Pregnancy
SynonymGestation
Pregnant woman.jpg
A pregnant woman
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 the last menstrual period[4][5]
CausesSexual intercourse, assisted reproductive technology[6]
Diagnostic methodPregnancy test[7]
PreventionBirth control, abortion[8]
TreatmentPrenatal care[9]
MedicationFolic acid, iron supplements[9][10]
Frequency213 million (2012)[11]
DeathsDecrease 230,600 (2016)[12]

Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman.[4] A multiple pregnancy involves more than one offspring, such as with twins.[13] Pregnancy can occur by sexual intercourse or assisted reproductive technology.[6] Childbirth typically occurs around 40 weeks from the last menstrual period (LMP).[4][5] This is just over nine months, where each month averages 31 days.[4][5] When measured from fertilization it is about 38 weeks.[5] An embryo is the developing offspring during the first eight weeks following fertilization, after which, the term fetus is used until birth.[5] Symptoms of early pregnancy may include missed periods, tender breasts, nausea and vomiting, hunger, and frequent urination.[1] Pregnancy may be confirmed with a pregnancy test.[7]

Pregnancy is typically divided into three trimesters.[4] The first trimester is from week one through 12 and includes conception, which is when the sperm fertilizes the egg.[4] The fertilized egg then travels down the fallopian tube and attaches to the inside of the uterus, where it begins to form the embryo and placenta.[4] During the first trimester, the possibility of miscarriage (natural death of embryo or fetus) is at its highest.[2] The second trimester is from week 13 through 28.[4] Around the middle of the second trimester, movement of the fetus may be felt.[4] At 28 weeks, more than 90% of babies can survive outside of the uterus if provided with high-quality medical care.[4] The third trimester is from 29 weeks through 40 weeks.[4]

Prenatal care improves pregnancy outcomes.[9] Prenatal care may include taking extra folic acid, avoiding drugs and alcohol, regular exercise, blood tests, and regular physical examinations.[9] Complications of pregnancy may include disorders of high blood pressure, gestational diabetes, iron-deficiency anemia, and severe nausea and vomiting among others.[3] In the ideal childbirth labor begins on its own when a woman is "at term".[14] Pregnancy is considered at full term when gestation has lasted 39 to 41 weeks.[4] After 41 weeks, it is known as late term and after 42 weeks post term.[4] Babies born before 39 weeks are considered early term while those before 37 weeks are preterm.[4] Preterm babies are at higher risk of health problems such as cerebral palsy.[4] Delivery before 39 weeks by labor induction or caesarean section is not recommended unless required for other medical reasons.[15]

About 213 million pregnancies occurred in 2012, of which, 190 million (89%) were in the developing world and 23 million (11%) were in the developed world.[11] The number of pregnancies in women ages 15 to 44 is 133 per 1,000 women.[11] About 10% to 15% of recognized pregnancies end in miscarriage.[2] In 2016, complications of pregnancy resulted in 230,600 deaths, down from 377,000 deaths in 1990.[12] Common causes include bleeding, infections, hypertensive diseases of pregnancy, obstructed labor, and complications associated with miscarriage, ectopic pregnancy, or elective abortion.[16] Globally, 44% of pregnancies are unplanned.[17] Over half (56%) of unplanned pregnancies are aborted.[17] Among unintended pregnancies in the United States, 60% of the women used birth control to some extent during the month pregnancy occurred.[18]

Terminology

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

Associated terms for pregnancy are gravid and parous. Gravidus and gravid come from the Latin for "heavy" and a pregnant female is sometimes referred to as a gravida.[19] Gravidity is a term used to describe the number of times that a female has been pregnant. Similarly, the term parity is used for the number of times that a female carries a pregnancy to a viable stage.[20] Twins and other multiple births are counted as one pregnancy and birth. A woman who has never been pregnant is referred to as a nulligravida. A woman who is (or has been only) pregnant for the first time is referred to as a primigravida,[21] and a woman in subsequent pregnancies as a multigravida or as multiparous.[19][22] Therefore, during a second pregnancy a woman would be described as gravida 2, para 1 and upon live delivery as gravida 2, para 2. In-progress pregnancies, abortions, miscarriages and/or stillbirths account for parity values being less than the gravida number. In the case of a multiple birth the gravida number and parity value are increased by one only. Women who have never carried a pregnancy achieving more than 20 weeks of gestation age are referred to as nulliparous.[23]

The terms preterm and postterm have largely replaced earlier terms of premature and postmature. Preterm and postterm are defined above, whereas premature and postmature have historical meaning and relate more to the infant's size and state of development rather than to the stage of pregnancy.[24][25]

Signs and symptoms

Melasma pigment changes to the face due to pregnancy

The usual symptoms and discomforts of pregnancy do not significantly interfere with activities of daily living or pose a health-threat to the mother or baby. However, pregnancy complications can cause other more severe symptoms, such as those associated with anemia.

Common symptoms and discomforts of pregnancy include: