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This article is about pregnancy in humans. For other mammals, seePregnancy (mammals).For fish, seePregnancy in fish.
"Trimester (pregnancy)" redirects here. For other uses of 'trimester', seeTrimester.
"Pregnant" redirects here. For the My Hero episode, seeList of My Hero episodes § ep12.

Pregnancy
Other namesGestation
A woman in the third trimester of pregnancy
SpecialtyObstetrics,midwifery
SymptomsMissed periods, tender breasts,nausea and vomiting,hunger, frequent urination[1]
ComplicationsMiscarriage,high blood pressure of pregnancy,gestational diabetes,iron-deficiency anemia,severe nausea and vomiting[2][3]
Duration~40 weeks from thelast menstrual period(38 weeks after conception)[4][5]
CausesSexual intercourse,assisted reproductive technology[6]
Diagnostic methodPregnancy test[7]
PreventionBirth control(includingemergency contraception)[8]
TreatmentPrenatal care,[9]abortion[8]
MedicationFolic acid,iron supplements[9][10]
Frequency213 million (2012)[11]
DeathsPositive decrease230,600 (2016)[12]

Pregnancyis the time during which one or moreoffspringdevelops (gestates) inside awoman'suterus(womb).[4][13]Amultiple pregnancyinvolves more than one offspring, such as withtwins.[14]

Pregnancy usually occurs bysexual intercourse,but can also occur throughassisted reproductive technologyprocedures.[6]A pregnancy may end in alive birth,amiscarriage,aninduced abortion,or astillbirth.Childbirthtypically occurs around 40 weeks from the start of thelast menstrual period(LMP), a span known as thegestational age.[4][5]This is just over nine months. Counting byfertilization age,the length is about 38 weeks.[5][13]Pregnancy is "the presence of an implanted human embryo or fetus in the uterus";implantationoccurs on average 8–9 days after fertilization.[15]Anembryois the term for the developing offspring during the first seven weeks following implantation (i.e. ten weeks' gestational age), after which the termfetusis used until birth.[5]

Signs and symptoms of early pregnancymay includemissed periods,tender breasts,morning sickness(nausea and vomiting), hunger,implantation bleeding,and frequent urination.[1]Pregnancy may be confirmed with apregnancy test.[7]Methods ofbirth control—or, more accurately,contraception—are used to avoid pregnancy.

Pregnancy is divided into three trimesters of approximately three months each. Thefirst trimesterincludes conception, which is when the sperm fertilizes the egg. Thefertilized eggthen travels down thefallopian tubeand attaches to the inside of theuterus,where it begins to form theembryoandplacenta.During the first trimester, the possibility of miscarriage (natural death of embryo or fetus) is at its highest. Around the middle of the second trimester, movement of the fetus may be felt. At 28 weeks, more than 90% of babies cansurvive outside of the uterusifprovided with high-quality medical care,though babies born at this time will likely experience serious health complications such as heart and respiratory problems and long-term intellectual and developmental disabilities.

Prenatal careimproves pregnancy outcomes.[9]Nutritionduring pregnancy is important to ensure healthy growth of the fetus.[16]Prenatal care may also include avoidingrecreational drugs(includingtobaccoandalcohol), taking regular exercise, havingblood tests,and regularphysical examinations.[9]Complications of pregnancymay includedisorders of high blood pressure,gestational diabetes,iron-deficiency anemia,andsevere nausea and vomiting.[3]In the ideal childbirth, labor begins on its own "at term".[17]Babies born before 37 weeks are "preterm"and at higher risk of health problems such ascerebral palsy.[4]Babies born between weeks 37 and 39 are considered "early term" while those born between weeks 39 and 41 are considered "full term".[4]Babies born between weeks 41 and 42 weeks are considered "late-term" while after 42 weeks they are considered "post-term".[4]Deliverybefore 39 weeks bylabor inductionorcaesarean sectionis not recommended unless required for other medical reasons.[18]

Terminology

Title page from an 18th-century book about pregnancy
William Hunter,Anatomia uteri humani gravidi tabulis illustrata,1774

Associated terms for pregnancy aregravidandparous.Gravidusandgravidcome from theLatinword meaning "heavy" and a pregnant female is sometimes referred to as agravida.[19]Gravidityrefers to the number of times that a female has been pregnant. Similarly, the termparityis used for the number of times that a female carries a pregnancy to aviable stage.[20]Twinsand other multiple births are counted as one pregnancy and birth.

A woman who has never been pregnant is referred to as anulligravida.A woman who is (or has been only) pregnant for the first time is referred to as aprimigravida,[21]and a woman in subsequent pregnancies as amultigravidaor asmultiparous.[19][22]Therefore, during a second pregnancy a woman would be described asgravida 2, para 1and upon live delivery asgravida 2, para 2.In-progress pregnancies,abortions,miscarriagesand/orstillbirthsaccount for parity values being less than the gravida number. Women who have never carried a pregnancy more than 20 weeks are referred to asnulliparous.[23]

A pregnancy is consideredtermat 37 weeks of gestation. It ispretermif less than 37 weeks andposttermat or beyond 42 weeks of gestation. American College of Obstetricians and Gynecologists have recommended further division withearly term37 weeks up to 39 weeks,full term39 weeks up to 41 weeks, andlate term41 weeks up to 42 weeks.[24]The termspretermandposttermhave largely replaced earlier terms ofprematureandpostmature.Pretermandposttermare defined above, whereasprematureandpostmaturehave historical meaning and relate more to the infant's size and state of development rather than to the stage of pregnancy.[25][26]

Demographics and statistics

About 213 million pregnancies occurred in 2012, of which, 190 million (89%) were in thedeveloping worldand 23 million (11%) were in the developed world.[11]The number of pregnancies in women aged between 15 and 44 is 133 per 1,000 women.[11]About 10% to 15% of recognized pregnancies end inmiscarriage.[2]In 2016,complications of pregnancyresulted in 230,600maternal deaths,down from 377,000 deaths in 1990.[12]Common causes includebleeding,infections,hypertensive diseases of pregnancy,obstructed labor,miscarriage, abortion, orectopic pregnancy.[12]Globally, 44% of pregnancies areunplanned.[27]Over half (56%) of unplanned pregnancies are aborted.[27]Among unintended pregnancies in the United States, 60% of the women usedbirth controlto some extent during the month pregnancy began.[28]

Signs and symptoms

Main article:Signs and symptoms of pregnancy
Further information:Complications of pregnancy
Melasma:pigment changes to the face due to pregnancy
In the later part of pregnancy the uterus takes up much of the abdomen.

The usualsigns and symptoms of pregnancydo not significantly interfere withactivities of daily livingor pose a health-threat to themotheror baby. However,pregnancy complicationscan cause other more severe symptoms, such as those associated withanemia.

Common signs and symptoms of pregnancy include:

Timeline

Comparison of dating systems for a typical pregnancy
Event Gestational age

(from the start of thelast menstrual period)

Fertilization age Implantation age
Menstrual periodbegins Day 1 of pregnancy Not pregnant Not pregnant
Hassexandovulates 2 weeks pregnant Not pregnant Not pregnant
Fertilization;cleavage stagebegins[32] Day 15[32] Day 1[32][33] Not pregnant
Implantationofblastocystbegins Day 20 Day 6[32][33] Day 0
Implantation finished Day 26 Day 12[32][33] Day 6 (orDay 0)
Embryostage begins; also, firstmissed period 4 weeks Day 15[32] Day 9
Primitive heart functioncan bedetected 5 weeks, 5 days[32] Day 26[32] Day 20
Fetal stagebegins 10 weeks, 1 day[32] 8 weeks, 1 day[32] 7 weeks, 2 days
First trimester ends 13 weeks 11 weeks 10 weeks
Second trimester ends 26 weeks 24 weeks 23 weeks
Childbirth 39–40 weeks 37–38 weeks[33]: 108  36–37 weeks

Thechronologyof pregnancy is, unless otherwise specified, generally given asgestational age,where the starting point is the beginning of the woman'slast menstrual period(LMP), or the corresponding age of the gestation as estimated by a more accurate method if available. This model means that the woman is counted as being "pregnant" two weeks beforeconceptionand three weeks beforeimplantation.Sometimes, timing may also use thefertilization age,which is the age of the embryo since conception.

Start of gestational age

Main article:Gestational age

TheAmerican Congress of Obstetricians and Gynecologistsrecommends the following methods to calculate gestational age:[34]

  • Directly calculating the days since the beginning of thelast menstrual period.
  • Earlyobstetric ultrasound,comparing the size of anembryoorfetusto that of areference groupof pregnancies of known gestational age (such as calculated from last menstrual periods), and using the mean gestational age of other embryos or fetuses of the same size. If the gestational age as calculated from an early ultrasound is contradictory to the one calculated directly from the last menstrual period, it is still the one from the early ultrasound that is used for the rest of the pregnancy.[34]
  • In case ofin vitro fertilization,calculating days sinceoocyte retrievalorco-incubationand adding 14 days.[35]

Trimesters

Pregnancy is divided into three trimesters, each lasting for approximately three months.[4]The exact length of each trimester can vary between sources.

  • Thefirst trimesterbegins with the start of gestational age as described above, that is, the beginning of week 1, or 0 weeks + 0 days of gestational age (GA). It ends at week 12 (11 weeks + 6 days of GA)[4]or end of week 14 (13 weeks + 6 days of GA).[36]
  • Thesecond trimesteris defined as starting, between the beginning of week 13 (12 weeks +0 days of GA)[4]and beginning of week 15 (14 weeks + 0 days of GA).[36]It ends at the end of week 27 (26 weeks + 6 days of GA)[36]or end of week 28 (27 weeks + 6 days of GA).[4]
  • Thethird trimesteris defined as starting, between the beginning of week 28 (27 weeks + 0 days of GA)[36]or beginning of week 29 (28 weeks + 0 days of GA).[4]It lasts untilchildbirth.
Timeline of pregnancy, including (from top to bottom): Trimesters, embryo/fetus development,gestational agein weeks and months, viability and maturity stages

Estimation of due date

Distribution ofgestational ageat childbirth among singleton live births, given both when gestational age is estimated by first trimester ultrasound and directly by last menstrual period.[37]Roughly 80% of births occur between 37 and 41 weeks of gestational age.
Main article:Estimated date of delivery

Due date estimationbasically follows two steps:

  • Determination of which time point is to be used asoriginforgestational age,as described in the section above.
  • Adding the estimated gestational age at childbirth to the above time point. Childbirth on average occurs at a gestational age of 280 days (40 weeks), which is therefore often used as a standard estimation for individual pregnancies.[38]However, alternative durations as well as more individualized methods have also been suggested.

TheAmerican College of Obstetricians and Gynecologistsdivides full term into three divisions:[39]

  • Early-term: 37 weeks and 0 days through 38 weeks and 6 days
  • Full-term: 39 weeks and 0 days through 40 weeks and 6 days
  • Late-term: 41 weeks and 0 days through 41 weeks and 6 days
  • Post-term: greater than or equal to 42 weeks and 0 days

Naegele's ruleis a standard way of calculating the due date for a pregnancy when assuming a gestational age of 280 days at childbirth. The rule estimates the expected date of delivery (EDD) by adding a year, subtracting three months, and adding seven days to the origin of gestational age. Alternatively there aremobile apps,which essentially always give consistent estimations compared to each other and correct forleap year,while pregnancy wheels made of paper can differ from each other by 7 days and generally do not correct for leap year.[40]

Furthermore, actual childbirth has only a certain probability of occurring within the limits of the estimated due date. A study of singleton live births came to the result that childbirth has astandard deviationof 14 days when gestational age is estimated by first trimesterultrasound,and 16 days when estimated directly by last menstrual period.[37]

Physiology

Capacity

Further information:Pregnancy over age 50

Fertilityandfecundityare the respective capacities tofertilizeand establish a clinical pregnancy and have a live birth.Infertilityis an impaired ability to establish a clinical pregnancy andsterilityis the permanent inability to establish a clinical pregnancy.[41]

The capacity for pregnancy depends on thereproductive system,its developmentandits variation,as well as on the condition of a person. Womenas well asintersexandtransgenderpeople who have a functioningfemale reproductive systemare capable of pregnancy. In some cases, someone might be able to produce fertilizable eggs, but might not have a womb or none that can sufficiently gestate, in which case they might findsurrogacy.[42]

Initiation

See also:Human fertilization
Fertilization and implantation in humans.

Through an interplay of hormones that includesfollicle stimulating hormonethat stimulatesfolliculogenesisandoogenesiscreates a matureegg cell,the femalegamete.Fertilizationis the event where the egg cell fuses with the male gamete,spermatozoon.After the point of fertilization, the fused product of the female and male gamete is referred to as azygoteor fertilized egg. The fusion of female and male gametes usually occurs following the act ofsexual intercourse.Pregnancy rates for sexual intercourseare highest during themenstrual cycletime from some 5 days before until 1 to 2 days after ovulation.[43]Fertilization can also occur byassisted reproductive technologysuch asartificial inseminationandin vitro fertilisation.

Fertilization (conception) is sometimes used as the initiation of pregnancy, with the derived age being termedfertilization age.Fertilization usually occurs about two weeks before thenextexpected menstrual period.

A third point in time is also considered by some people to be the true beginning of a pregnancy: This is time of implantation, when the future fetus attaches to the lining of the uterus. This is about a week to ten days after fertilization.[44]

Development of embryo and fetus

Main articles:Human embryonic development,Prenatal development,andFetus
The initial stages ofhuman embryogenesis

The sperm and the egg cell, which has been released from one of the female's twoovaries,unite in one of the twofallopian tubes.The fertilized egg, known as azygote,then moves toward the uterus, a journey that can take up to a week to complete. Cell division begins approximately 24 to 36 hours after the female and male cells unite. Cell division continues at a rapid rate and the cells then develop into what is known as ablastocyst.The blastocyst arrives at the uterus and attaches to the uterine wall, a process known asimplantation.

The development of the mass of cells that will become the infant is calledembryogenesisduring the first approximately ten weeks of gestation. During this time, cells begin to differentiate into the various body systems. The basic outlines of the organ, body, and nervous systems are established. By the end of the embryonic stage, the beginnings of features such as fingers, eyes, mouth, and ears become visible. Also during this time, there is development of structures important to the support of the embryo, including theplacentaandumbilical cord.The placenta connects the developing embryo to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. The umbilical cord is the connecting cord from the embryo or fetus to the placenta.

After about ten weeks of gestational age—which is the same as eight weeks after conception—the embryo becomes known as afetus.[45]At the beginning of the fetal stage, the risk of miscarriage decreases sharply.[46]At this stage, a fetus is about 30 mm (1.2 inches) in length, the heartbeat is seen via ultrasound, and the fetus makes involuntary motions.[47]During continued fetal development, the early body systems, and structures that were established in the embryonic stage continue to develop. Sex organs begin to appear during the third month of gestation. The fetus continues to grow in both weight and length, although the majority of the physical growth occurs in the last weeks of pregnancy.

Electricalbrain activityis first detected at the end of week 5 of gestation, but as inbrain-deadpatients, it is primitive neural activity rather than the beginning of conscious brain activity. Synapses do not begin to form until week 17.[48]Neural connections between thesensory cortexandthalamusdevelop as early as 24 weeks' gestational age, but the first evidence of their function does not occur until around 30 weeks, when minimalconsciousness,dreaming,and the ability to feel pain emerges.[49]

Although the fetus begins to move during the first trimester, it is not until the second trimester that movement, known asquickening,can be felt. This typically happens in the fourth month, more specifically in the 20th to 21st week, or by the 19th week if the woman has been pregnant before. It is common for some women not to feel the fetus move until much later. During the second trimester, when the body size changes,maternity clothesmay be worn.

  • Embryo at 4 weeks after fertilization (gestational age of 6 weeks)
    Embryo at 4 weeks after fertilization (gestational age of 6 weeks)
  • Fetus at 8 weeks after fertilization (gestational age of 10 weeks)
    Fetus at 8 weeks after fertilization (gestational age of 10 weeks)
  • Fetus at 18 weeks after fertilization (gestational age of 20 weeks)
    Fetus at 18 weeks after fertilization (gestational age of 20 weeks)
  • Fetus at 38 weeks after fertilization (gestational age of 40 weeks)
    Fetus at 38 weeks after fertilization (gestational age of 40 weeks)
  • Relative size in 1st month (simplified illustration)
    Relative size in 1st month (simplified illustration)
  • Relative size in 3rd month (simplified illustration)
    Relative size in 3rd month (simplified illustration)
  • Relative size in 5th month (simplified illustration)
    Relative size in 5th month (simplified illustration)
  • Relative size in 9th month (simplified illustration)
    Relative size in 9th month (simplified illustration)

Maternal changes

Theuterusexpands making up a larger and larger portion of the abdomen. During the final stages of gestation the uterus may drop to a lower position.
Main article:Maternal physiological changes in pregnancy
Breast changes as seen during pregnancy. The areolae are larger and darker.

During pregnancy, a woman undergoes many normalphysiologicalchanges, includingbehavioral,cardiovascular,hematologic,metabolic,renal,andrespiratorychanges. Increases inblood sugar,breathing,andcardiac outputare all required. Levels ofprogesteroneandestrogensrise continually throughout pregnancy, suppressing thehypothalamic axisand therefore themenstrual cycle.A full-term pregnancy at an early age (less than 25 years) reduces the risk ofbreast,ovarian,andendometrial cancer,and the risk declines further with each additional full-term pregnancy.[50][51]

End of second trimester + 2 weeks (26 weeks of pregnancy)

The fetus isgeneticallydifferent from its mother and can therefore be viewed as an unusually successfulallograft.[52]The main reason for this success is increasedimmune toleranceduring pregnancy,[53]which prevents the mother's body from mounting animmune system responseagainst certain triggers.[52]

During the first trimester,minute ventilationincreases by 40 percent.[54]The womb will grow to the size of alemonby eight weeks. Manysymptoms and discomforts of pregnancy,such as nausea andtender breasts,appear in the first trimester.[55]

During the second trimester, most women feel more energized and put on weight as the symptoms ofmorning sicknesssubside. They begin to feel regularfetal movements,which can become strong and even disruptive.[citation needed]

Braxton Hicks contractionsare sporadicuterine contractionsthat may start around six weeks into a pregnancy; however, they are usually not felt until the second or third trimester.[56]

Final weight gain takes place during the third trimester; this is the most weight gain throughout the pregnancy. The woman's abdomen will transform in shape as the fetus turns in a downward position ready for birth. The woman'snavelwill sometimes become convex, "popping" out, due to the expandingabdomen.The uterus, the muscular organ that holds the developing fetus, can expand up to 20 times its normal size during pregnancy.

Head engagement,also called "lightening" or "dropping", occurs as the fetal head descends into acephalic presentation.While it relieves pressure on the upper abdomen and gives a renewed ease in breathing, it also severely reduces bladder capacity, resulting in a need tovoid more frequently,and increases pressure on the pelvic floor and the rectum. It is not possible to predict when lightening will occur. In a first pregnancy it may happen a few weeks before the due date, though it may happen later or even not until labor begins, as is typical with subsequent pregnancies.[57]

It is during the third trimester that maternal activity and sleep positions may affectfetal developmentdue to restrictedblood flow.For instance, the enlarged uterus may impede blood flow by compressing thevena cavawhen lying flat, a condition that can be relieved by lying on the left side.[58]

Childbirth

Main article:Childbirth

Childbirth, referred to as labor and delivery in the medical field, is the process whereby an infant is born.[59]

A woman is considered to be in labor when she begins experiencing regular uterine contractions, accompanied by changes of her cervix—primarily effacement and dilation. While childbirth is widely experienced as painful, some women do report painless labors, while others find that concentrating on the birth helps to quicken labor and lessen the sensations. Most births are successful vaginal births, but sometimes complications arise and a woman may undergo acesarean section.

During the time immediately after birth, both the mother and thebabyare hormonally cued to bond, the mother through the release ofoxytocin,a hormone also released duringbreastfeeding.Studies show that skin-to-skin contact between a mother and her newborn immediately after birth is beneficial for both the mother and baby. A review done by theWorld Health Organizationfound that skin-to-skin contact between mothers and babies after birth reduces crying, improves mother–infant interaction, and helps mothers to breastfeed successfully. They recommend thatneonatesbe allowed to bond with the mother during their first two hours after birth, the period that they tend to be more alert than in the following hours of early life.[60]

Childbirth maturity stages

Further information:Preterm birthandPostterm pregnancy

Stages of pregnancy term
stage starts ends
Preterm[61] - at 37 weeks
Early term[62] 37 weeks 39 weeks
Full term[62] 39 weeks 41 weeks
Late term[62] 41 weeks 42 weeks
Postterm[62] 42 weeks -

In the idealchildbirth,labor begins on its own when a woman is "at term".[17] Events before completion of 37 weeks are considered preterm.[61]Preterm birthis associated with a range of complications and should be avoided if possible.[63]

Sometimes if a woman'swater breaksor she hascontractionsbefore 39 weeks, birth is unavoidable.[62]However, spontaneous birth after 37 weeks is considered term and is not associated with the same risks of a preterm birth.[59]Planned birth before 39 weeks bycaesarean sectionorlabor induction,although "at term", results in an increased risk of complications.[64]This is from factors includingunderdeveloped lungs of newborns,infection due to underdeveloped immune system, feeding problems due to underdeveloped brain, andjaundicefrom underdeveloped liver.[65]

Babies born between 39 and 41 weeks' gestation have better outcomes than babies born either before or after this range.[62]This special time period is called "full term".[62]Whenever possible, waiting for labor to begin on its own in this time period is best for the health of the mother and baby.[17]The decision to perform an induction must be made after weighing the risks and benefits, but is safer after 39 weeks.[17]

Events after 42 weeks are consideredpostterm.[62]When a pregnancy exceeds 42 weeks, the risk of complications for both the woman and the fetus increases significantly.[66][67]Therefore, in an otherwise uncomplicated pregnancy, obstetricians usually prefer to induce labor at some stage between 41 and 42 weeks.[68]

Postnatal period

Main article:Postpartum period

Thepostpartum periodalso referred to as thepuerperium,is the postnatal period that begins immediately after delivery and extends for about six weeks.[59]During this period, the mother's body begins the return to pre-pregnancy conditions that includes changes in hormone levels and uterus size.[59]

Diagnosis

The beginning of pregnancy may be detected either based on symptoms by the woman herself, or by usingpregnancy tests.However, an important condition with serious health implications that is quite common is thedenial of pregnancyby the pregnant woman. About 1 in 475 denials will last until around the 20th week of pregnancy. The proportion of cases of denial, persisting until delivery is about 1 in 2500.[69]Conversely, some non-pregnant women have a very strong belief that they are pregnant along with some of the physical changes. This condition is known as afalse pregnancy.[70]

Physical signs

Further information:Signs and symptoms of pregnancy
Linea nigrain a woman at 22 weeks pregnant

Most pregnant women experience a number of symptoms,[71]which can signify pregnancy. A number of earlymedical signsare associated with pregnancy.[72][73]These signs include:

Biomarkers

Further information:Pregnancy test

Pregnancy detection can be accomplished using one or more variouspregnancy tests,[75]which detect hormones generated by the newly formedplacenta,serving asbiomarkersof pregnancy.[76]Blood and urine tests can detect pregnancy by 11 and 14 days, respectively, after fertilization.[77][78]Blood pregnancy tests are moresensitivethan urine tests (giving fewer false negatives).[79]Home pregnancy tests are urine tests, and normally detect a pregnancy 12 to 15 days after fertilization.[80]A quantitative blood test can determine approximately the date the embryo was fertilized becausehCGlevels double every 36 to 72 hours before 8 weeks' gestation.[59][78]A single test ofprogesteronelevels can also help determine how likely a fetus will survive in those with athreatened miscarriage(bleeding in early pregnancy), but only if the ultrasound result was inconclusive.[81]

Ultrasound

Main article:Obstetric ultrasonography

Obstetric ultrasonographycan detectfetal abnormalities,detectmultiple pregnancies,and improve gestational dating at 24 weeks.[82]The resultant estimatedgestational ageand due date of the fetus are slightly more accurate than methods based on last menstrual period.[83]Ultrasound is used to measure thenuchal foldin order to screen forDown syndrome.[84]

Management

An infographic showing a flow chart leading to three diagrams, each showing two human figures depicting different lengths of gestation, with a grid showing weight limits for different locations in front of the body
Flowchart showing the recommended weight limits for lifting at work during pregnancy as a function of lifting frequency, weeks of gestation, and the position of the lifted object relative to the lifter's body.[85][86]

Prenatal care

Main articles:Prenatal careandpre-conception counseling

Pre-conception counselingis care that is provided to a woman or couple to discuss conception, pregnancy, current health issues and recommendations for the period before pregnancy.[87]

Prenatal medical careis the medical and nursing care recommended for women during pregnancy, time intervals and exact goals of each visit differ by country.[88]Women who are high risk have better outcomes if they are seen regularly and frequently by a medical professional than women who are low risk.[89]A woman can be labeled as high risk for different reasons including previous complications in pregnancy, complications in the current pregnancy, current medical diseases, or social issues.[90][91]

The aim of good prenatal care is prevention, early identification, and treatment of any medical complications.[92]A basic prenatal visit consists of measurement of blood pressure,fundal height,weight and fetal heart rate, checking for symptoms of labor, and guidance for what to expect next.[87]

Nutrition

Main article:Nutrition and pregnancy

Nutritionduring pregnancy is important to ensure healthy growth of the fetus.[16]Nutrition during pregnancy is different from the non-pregnant state.[16]There are increased energy requirements and specific micronutrient requirements.[16]Women benefit from education to encourage a balanced energy and protein intake during pregnancy.[93]Some women may need professional medical advice if their diet is affected by medical conditions, food allergies, or specific religious/ ethical beliefs.[94]Further studies are needed to access the effect of dietary advice to preventgestational diabetes,although low quality evidence suggests some benefit.[95]Adequate periconceptional (time before and right after conception)folic acid(also called folate or Vitamin B9) intake has been shown to decrease the risk of fetal neural tube defects, such asspina bifida.[96]The neural tube develops during the first 28 days of pregnancy, a urine pregnancy test is not usually positive until 14 days post-conception, explaining the necessity to guarantee adequate folate intake before conception.[80][97]Folate is abundant ingreen leafy vegetables,legumes,andcitrus.[98]In the United States and Canada, most wheat products (flour, noodles) are fortified with folic acid.[99]

Weight gain

Weight gain during pregnancy
Measurement of the belly and weight are both performed by pregnant women during her pregnancy

The amount of healthy weight gain during a pregnancy varies.[100]Weight gain is related to the weight of the baby, the placenta, extra circulatory fluid, larger tissues, and fat and protein stores.[16]Most needed weight gain occurs later in pregnancy.[101]

TheInstitute of Medicinerecommends an overall pregnancy weight gain for those of normal weight (body mass indexof 18.5–24.9), of 11.3–15.9 kg (25–35 pounds) having a singleton pregnancy.[102]Women who are underweight (BMI of less than 18.5), should gain between 12.7 and 18 kg (28–40 lb), while those who areoverweight(BMI of 25–29.9) are advised to gain between 6.8 and 11.3 kg (15–25 lb) and those who areobese(BMI ≥ 30) should gain between 5–9 kg (11–20 lb).[103]These values reference the expectations for a term pregnancy.

During pregnancy, insufficient or excessive weight gain can compromise the health of the mother and fetus.[101]The most effective intervention for weight gain in underweight women is not clear.[101]Being or becoming overweight in pregnancy increases the risk of complications for mother and fetus, includingcesarean section,gestational hypertension,pre-eclampsia,macrosomiaandshoulder dystocia.[100]Excessive weight gain can make losing weight after the pregnancy difficult.[100][104]Some of these complications are risk factors forstroke.[105]

Around 50% of women of childbearing age in developed countries like the United Kingdom are overweight or obese before pregnancy.[104]Diet modification is the most effective way to reduce weight gain and associated risks in pregnancy.[104]

Medication

Main article:Pharmaceutical drugs in pregnancy

Drugs used during pregnancy can have temporary or permanent effects on the fetus.[106]Anything (including drugs) that can cause permanent deformities in the fetus are labeled asteratogens.[107]In the U.S., drugs were classified into categories A, B, C, D and X based on theFood and Drug Administration(FDA) rating system to provide therapeutic guidance based on potential benefits and fetal risks.[108]Drugs, including somemultivitamins,that have demonstrated no fetal risks after controlled studies in humans are classified as Category A.[106]On the other hand, drugs likethalidomidewith proven fetal risks that outweigh all benefits are classified as Category X.[106]

Recreational drugs

See also:Neonatal withdrawal

The use ofrecreational drugsin pregnancy can cause variouspregnancy complications.[59]

Exposure to toxins

Further information:Environmental toxicants and fetal development
A video describing research onN95 respiratoruse during advanced pregnancy

Intrauterine exposure toenvironmental toxins in pregnancyhas the potential to cause adverse effects onprenatal development,and to causepregnancy complications.[59]Air pollution has been associated with low birth weight infants.[115]Conditions of particular severity in pregnancy includemercury poisoningandlead poisoning.[59]To minimize exposure to environmental toxins, the American College of Nurse-Midwives recommends: checking whether the home haslead paint,washing all freshfruitsandvegetablesthoroughly and buyingorganicproduce, and avoiding cleaning products labeled "toxic" or any product with a warning on the label.[116]

Pregnant women can also be exposed totoxins in the workplace,including airborne particles. The effects of wearing anN95 filtering facepiece respiratorare similar for pregnant women as for non-pregnant women, and wearing a respirator for one hour does not affect the fetal heart rate.[117]

Death by violence

Pregnant women or those who have recently given birth in the U.S. aremore likely to be murderedthan to die from obstetric causes. These homicides are a combination of intimate partner violence and firearms. Health authorities have called the violence "a health emergency for pregnant women", but say that pregnancy-related homicides are preventable if healthcare providers identify those women at risk and offer assistance to them.[118][119][120]

Sexual activity

Main article:Sexual activity during pregnancy

Most women can continue to engage in sexual activity, includingsexual intercourse,throughout pregnancy.[121]Research suggests that during pregnancy both sexual desire and frequency of sexual relations decrease during the first and third trimester, with a rise during the second trimester.[122][123][124][125]Sex during pregnancy is a low-risk behavior except when the healthcare provider advises that sexual intercourse be avoided for particular medical reasons.[121]For a healthy pregnant woman, there is no singlesafeorrightway to have sex during pregnancy.[121]

Exercise

A pregnant woman and her colleague returning from fishing, Gurara River bridge,Kachia,Nigeria.

Regularaerobic exerciseduring pregnancy appears to improve (or maintain) physical fitness.[126]Physical exerciseduring pregnancy appears to decrease the need forC-section,[127]and even vigorous exercise carries no significant risks to babies[128]and provides significant health benefits to the mother.[129]Bed rest,outside of research studies, is not recommended as there is no evidence of benefit and potential harm.[130]

The Clinical Practice Obstetrics Committee of Canada recommends that "All women without contraindications should be encouraged to participate in aerobic and strength-conditioning exercises as part of a healthy lifestyle during their pregnancy".[131]Although an upper level of safe exercise intensity has not been established, women who were regular exercisers before pregnancy and who have uncomplicated pregnancies should be able to engage in high intensity exercise programs, without a higher risk of prematurity, lower birth weight, or gestational weight gain.[128]In general, participation in a wide range of recreational activities appears to be safe, with the avoidance of those with a high risk of falling such as horseback riding or skiing or those that carry a risk of abdominal trauma, such as soccer or hockey.[132]

The American College of Obstetricians and Gynecologistsreports that in the past, the main concerns of exercise in pregnancy were focused on the fetus and any potential maternal benefit was thought to be offset by potential risks to the fetus. However, they write that more recent information suggests that in the uncomplicated pregnancy, fetal injuries are highly unlikely.[132]They do, however, list several circumstances when a woman should contact her healthcare provider before continuing with an exercise program: vaginal bleeding,dyspneabefore exertion, dizziness, headache, chest pain, muscle weakness, preterm labor, decreased fetal movement, amniotic fluid leakage, and calf pain or swelling (to rule outthrombophlebitis).[132]

Sleep

Main article:Pregnancy and sleep

It has been suggested thatshift workand exposure to bright light at night should be avoided at least during the last trimester of pregnancy to decrease the risk of psychological and behavioral problems in the newborn.[133]

Stress

The children of women who had high stress levels during pregnancy are slightly more likely to haveexternalizing behavioral problemssuch as impulsivity.[134]The behavioral effect was most pronounced during early childhood.[134]

Dental care

See also:Prenatal dental care

The increased levels ofprogesteroneandestrogenduring pregnancy makegingivitismore likely; thegumsbecome edematous, red in colour, and tend to bleed.[135]Also apyogenic granulomaor "pregnancy tumor", is commonly seen on the labial surface of the papilla. Lesions can be treated by local debridement or deep incision depending on their size, and by following adequateoral hygienemeasures.[136]There have been suggestions that severeperiodontitismay increase the risk of havingpreterm birthandlow birth weight;however, a Cochrane review found insufficient evidence to determine ifperiodontitiscan develop adverse birth outcomes.[137]

Flying

In low risk pregnancies, most health care providers approve flying until about 36 weeks of gestational age.[138]Most airlines allow pregnant women to fly short distances at less than 36 weeks, and long distances at less than 32 weeks.[139]Many airlines require a doctor's note that approves flying, especially at over 28 weeks.[139]During flights, the risk ofdeep vein thrombosisis decreased by getting up and walking occasionally, as well as by avoiding dehydration. The exposure to cosmic radiation is negligible for most travelers. For pregnant women, even the longest intercontinental fight would expose them less than 15% of both theNCRPMandICRPlimit.[140][139]Full body scannersdo not use ionizing radiation, and are safe in pregnancy.[141]

Pregnancy classes and birth plan

Main article:Birthing classes and birth plans

To prepare for the birth of the baby, health care providers recommend that parents attend antenatal classes during the third trimester of pregnancy. Classes include information about the process of labor and birth and the various kinds of births, including both vaginal andcaesarean delivery,the use of forceps, and other interventions that may be needed to safely deliver the infant. Types of pain relief, including relaxation techniques, are discussed. Partners or others who may plan to support a woman during her labor and delivery learn how to assist in the birth.[citation needed]

It is also suggested that a birth plan be written at this time. A birth plan is a written statement that outlines the desires of the mother during labor and delivery of the baby. Discussing the birth plan with the midwife or other care provider gives parents a chance to ask questions and learn more about the process of labour.[142]

In 1991 theWHOlaunched theBaby-Friendly Hospital Initiative,a global program that recognizes birthing centers and hospitals that offer optimal levels of care for giving birth. Facilities that have been certified as "Baby Friendly" accept visits from expecting parents to familiarize them with the facility and the staff.[143]

Complications

Main article:Complications of pregnancy

Each year, ill health as a result of pregnancy is experienced (sometimes permanently) by more than 20 million women around the world.[144]In 2016, complications of pregnancy resulted in 230,600 deaths down from 377,000 deaths in 1990.[12]Common causes includebleeding(72,000),infections(20,000),hypertensive diseases of pregnancy(32,000),obstructed labor(10,000), andpregnancy with abortive outcome(20,000), which includesmiscarriage,abortion,andectopic pregnancy.[12]

The following are some examples of pregnancy complications:

There is also an increasedsusceptibility and severity of certain infections in pregnancy.

Miscarriage and stillbirth

Main articles:MiscarriageandStillbirth
See also:Miscarriage and grief

Miscarriage is the most common complication of early pregnancy. It is defined as the loss of an embryo or fetus before it is able to survive independently. The most common symptom of miscarriage is vaginal bleeding with or without pain. The miscarriage may be evidenced by a clot-like material passing through and out of the vagina.[149]About 80% of miscarriages occur in the first 12 weeks of pregnancy. The underlying cause in about half of cases involves chromosomal abnormalities.[150]

Stillbirth is defined as fetal death after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. Each year about 21,000 babies are stillborn in the U.S.[151]Sadness, anxiety, and guilt may occur after a miscarriage or a stillbirth. Emotional support may help with processing the loss.[152]Fathers may experience grief over the loss as well. A large study found that there is a need to increase the accessibility of support services available for fathers.[153]

Diseases in pregnancy

Further information:Pre-existing disease in pregnancy

A pregnant woman may have apre-existing disease,which is not directly caused by the pregnancy, but may causecomplicationsto develop that include a potential risk to the pregnancy; or a disease may develop during pregnancy.

Abortion

Main article:Abortion

An abortion is the termination of an embryo or fetus via medical method. It is usually done within the first trimester, sometimes in the second, and rarely in the third. Reasons forpregnancies being undesiredare broad,[158]rapebeing the most legally accepted.[159]

Birth control and education

Main article:Birth control

Family planning,as well as the availability and use ofcontraception,along with increasedcomprehensive sex education,has enabled many to prevent pregnancies when they are not desired. Schemes and funding to support education and the means to prevent pregnancies when they are not intended have been instrumental and are part of the third of theSustainable Development Goals(SDGs) advanced by theUnited Nations.[160]

Technologies and science

Further information:Obstetrics

Assisted reproductive technology

Main article:Assisted reproductive technology

Modern reproductive medicine offers many forms of assisted reproductive technology for couples who stay childless against their will, such asfertility medication,artificial insemination,in vitrofertilizationandsurrogacy.

Medical imaging

CT scanning(volume renderedin this case) confers aradiation doseto the developing fetus.
A pregnant woman undergoing anultrasound.Ultrasound is used to check on the growth and development of the fetus.
Main article:Medical imaging in pregnancy

Medical imagingmay beindicatedin pregnancy because ofpregnancy complications,disease, or routineprenatal care.Medical ultrasonographyincludingobstetric ultrasonography,andmagnetic resonance imaging (MRI)withoutcontrast agentsare not associated with any risk for the mother or the fetus, and are the imaging techniques of choice for pregnant women.[161]Projectional radiography,CT scanandnuclear medicine imagingresult in some degree ofionizing radiationexposure, but in most cases theabsorbed dosesare not associated with harm to the baby.[161]At higher dosages or frequency, effects can includemiscarriage,birth defectsandintellectual disability.[161]

Epidemiology

See also:Pregnancy rateandAdvanced maternal age

About 213 million pregnancies occurred in 2012 of which 190 million were in thedeveloping worldand 23 million were in the developed world.[11]This is about 133 pregnancies per 1,000 women aged 15 to 44.[11]About 10% to 15% of recognized pregnancies end in miscarriage.[2]Globally, 44% of pregnancies areunplanned.Over half (56%) of unplanned pregnancies are aborted. In countries whereabortion is prohibited,or only carried out in circumstances where the mother's life is at risk, 48% of unplanned pregnancies areaborted illegally.Compared to the rate in countries where abortion is legal, at 69%.[27]

Of pregnancies in 2012, 120 million occurred in Asia, 54 million in Africa, 19 million in Europe, 18 million in Latin America and the Caribbean, 7 million in North America, and 1 million inOceania.[11]Pregnancy rates are 140 per 1000 women of childbearing age in the developing world and 94 per 1000 in the developed world.[11]

The rate of pregnancy, as well as the ages at which it occurs, differ by country and region. It is influenced by a number of factors, such as cultural, social and religious norms; access to contraception; and rates of education. Thetotal fertility rate(TFR) in 2013 was estimated to be highest inNiger(7.03 children/woman) and lowest inSingapore(0.79 children/woman).[162]

In Europe, the average childbearing age has been rising continuously for some time. In Western, Northern, and Southern Europe, first-time mothers are on average 26 to 29 years old, up from 23 to 25 years at the start of the 1970s. In a number of European countries (Spain), the mean age of women at first childbirth has crossed the 30-year threshold.

This process is not restricted to Europe. Asia, Japan and the United States are all seeing average age at first birth on the rise, and increasingly the process is spreading to countries in the developing world like China, Turkey and Iran. In the US, the average age of first childbirth was 25.4 in 2010.[163]

In the United States and United Kingdom, 40% of pregnancies areunplanned,and between a quarter and half of those unplanned pregnancies wereunwanted pregnancies.[164][165]

In the US, a woman's educational attainment and her marital status are correlated with childbearing: the percentage of women unmarried at the time of first birth drops with increasing educational level. In other words: among uneducated women, a large fraction (~80%) have their first child while they are unmarried. By contrast, few women with a bachelor's degree or higher (~25%) have their first child while unmarried. However, this phenomenon also has a strong generational component: in 1996, about 50% of women without a university degree had their first child being unmarried while that number increased to ~85% in 2018. Similarly, in 1996, only 4% of women with a BA degree or similar had their first child being unmarried. In 2018, that fraction increased to ~25%.[166]

Further information:Reproductive rightsandReproductive justice

Many countries have various legal regulations in place to protect pregnant women and their children. Many countries have laws againstpregnancy discrimination.[167]

Maternity Protection Conventionensures that pregnant women are exempt from activities such as night shifts or carrying heavy stocks.Maternity leavetypically provides paid leave from work during roughly the last trimester of pregnancy and for some time after birth. Notable extreme cases include Norway (8 months with full pay) and the United States (no paid leave at all except in some states).

In the United States, some actions that result in miscarriage or stillbirth, such as beating a pregnant woman, are considered crimes. One law that does so is the federalUnborn Victims of Violence Act.In 2014, the American state ofTennesseepassed a law which allows prosecutors to charge a woman with criminal assault if she uses illegal drugs during her pregnancy and her fetus or newborn is harmed as a result.[168]

However, protections are not universal. InSingapore,theEmployment of Foreign Manpower Actforbids current and formerwork permitholders from becoming pregnant or giving birth in Singapore without prior permission.[169][170]Violation of the Act is punishable by a fine of up toS$10,000 (US$7300) anddeportation,[169][171]and until 2010, their employers would lose their $5,000 security bond.[172]

Teenage pregnancy

Main article:Teenage pregnancy

Teenage pregnancyis also known asadolescentpregnancy.[173]TheWHOdefines adolescence as the period between the ages of 10 and 19 years.[174]Adolescents face higher health risks than women who give birth at age 20 to 24 and their infants are at a higher risk for preterm birth, low birth weight, and other severe neonatal conditions. Their children continue to face greater challenges, both behavioral and physical, throughout their lives. Teenage pregnancies are also related to social issues, including social stigma, lower educational levels, and poverty.[175][173]Studies show that female adolescents are often in abusive relationships at the time of their conceiving.[176]

Nurse-Family Partnership(NFP) is a non-profit organization operating in the United States and the UK designed to serve the needs of low income young mothers who may have special needs in their first pregnancy. Each mother served is partnered with a registered nurse early in her pregnancy and receives ongoing nurse home visits that continue through her child's second birthday. NFP intervention has been associated with improvements in maternal health, child health, and economic security.[177][178]

Racial disparities

There are significant racial imbalances in pregnancy and neonatal care systems.[179]Midwifery guidance, treatment, and care have been related to better birth outcomes. Diminishing racial inequities in health is an increasingly large public health challenge in the United States. Despite the fact that average rates have decreased, data on neonatal mortality demonstrates that racial disparities have persisted and grown. The death rate for African American babies is nearly double that of white neonates. According to studies,congenital defects,SIDS,preterm birth,andlow birth weightare all more common among African American babies.[180]

Midwifery care has been linked to better birth and postpartum outcomes for both mother and child. It caters to the needs of the woman and provides competent, sympathetic care, and is essential for maternal health improvement. The presence of adoula,or birth assistant, during labor and delivery, has also been associated with improved levels of satisfaction with medical birth care. Providers recognized their profession from a historical standpoint, a link to African origins, the diaspora, and prevailing African American struggles. Providers participated in both direct clinical experience and activist involvement. Advocacy efforts aimed to enhance the number of minority birth attendants and to promote the benefits of woman-centered birth care to neglected areas.[180]

Transgender people

Main article:Transgender pregnancy

Transgender people have experienced significant advances in societal acceptance in recent years leaving many health professionals unprepared to provide quality care. A 2015 report suggests that "numbers of transgender individuals who are seeking family planning, fertility, and pregnancy services could certainly be quite large". Regardless of prior hormone replacement therapy treatments, the progression of pregnancy and birthing procedures fortransgender people who carry pregnanciesare typically the same as those ofcisgenderwomen[181]however, they may be subjected to discrimination, which can include a variety of negative social, emotional, and medical experiences, as pregnancy is regarded as an exclusively female activity. According to a study by theAmerican College of Obstetricians and Gynecologists,there is a lack of awareness, services, and medical assistance available to pregnant trans men.[182]

Culture

The Visitation:Mary,pregnant withJesus,visiting pregnantElizabeth,depicted as a statue at theChurch of the VisitationinEin Karem,Israel.

In most cultures, pregnant women have a special status in society and receive particularly gentle care.[183]At the same time, they are subject to expectations that may exert great psychological pressure, such as having to produce a son and heir. In many traditional societies, pregnancy must be preceded by marriage, on pain of ostracism of mother and(illegitimate) child.

Overall, pregnancy is accompanied by numerous customs that are often subject to ethnological research, often rooted intraditional medicineor religion. Thebaby showeris an example of a modern custom. Contrary tocommon misconception,women historically in theUnited Stateswere not expected to seclude themselves during pregnancy, as was popularized byGone With the Wind.[184][185]

Pregnancy is an important topic insociology of the family.The prospective child may preliminarily be placed into numeroussocial roles.The parents' relationship and the relation between parents and their surroundings are also affected.

Abelly castmay be made during pregnancy as a keepsake.

Arts

Main article:Pregnancy in art

Images of pregnant women, especially smallfigurines,were made in traditional cultures in many places and periods, though it is rarely one of the most common types of image. These include ceramic figures from somePre-Columbiancultures, and a few figures from most of the ancient Mediterranean cultures. Many of these seem to be connected withfertility.Identifying whether such figures are actually meant to show pregnancy is often a problem, as well as understanding their role in the culture concerned.

Among the oldest surviving examples of the depiction of pregnancy are prehistoric figurines found across much ofEurasiaand collectively known asVenus figurines.Some of these appear to be pregnant.

Due to the important role of theMother of GodinChristianity,the Western visual arts have a long tradition of depictions of pregnancy, especially in the biblical scene of theVisitation,and devotional images called aMadonna del Parto.[186]

The unhappy scene usually calledDiana and Callisto,showing the moment of discovery ofCallisto's forbidden pregnancy, is sometimes painted from the Renaissance onwards. Gradually, portraits of pregnant women began to appear, with a particular fashion for "pregnancy portraits" in elite portraiture of the years around 1600.

Pregnancy, and especially pregnancy of unmarried women, is also an important motif in literature. Notable examples includeThomas Hardy's 1891 novelTess of the d'Urbervillesand Goethe's 1808 playFaust.

See also

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