Last updated: January 3, 2023

Summarytoggle arrow icon

Pregnancy begins with the fertilization of the ovum and its subsequent implantation into the uterine wall. The duration of pregnancy is counted in weeks of gestation from the first day of the last menstrual period and on average lasts 40 weeks. Presumptive signs of pregnancy include amenorrhea, nausea and vomiting, and breast enlargement and tenderness. Preconception counseling assists in the planning of pregnancy through education and risk assessment to help ensure best possible outcomes. Pregnancy can be confirmed definitively via positive serum or urine hCG tests and detection of the embryo on ultrasound. Ultrasound is also used to determine the gestational age and date of delivery. Women experience several physiological changes during pregnancy (e.g., increased plasma volume, venous stasis, increased insulin secretion, increased oxygen demand), which can lead to symptoms and conditions that may require treatment (e.g., peripheral edema, insulin resistance, hypercoagulability, dyspnea). Regular check-ups should be performed to detect potential high-risk pregnancies as well as fetal and maternal complications.

See also “Prenatal care” and “Maternal complications during pregnancy.”

Gravidity, parity, and duration of pregnancy [1]

  • Gravidity: the number of times a woman has been pregnant, regardless of pregnancy outcome
    • Nulligravidity: no history of pregnancy
    • Primigravidity: history of one pregnancy
    • Multigravidity: history of two or more pregnancies
  • Parity: the number of pregnancies that a woman carries beyond 20 weeks of gestation and ends with the birth of an infant weighing > 500 g
    • Nulliparity: no history of a completed pregnancy that reached beyond 20 weeks' gestation or ended with a birth weight of > 500 g
    • Primiparity: a history of one completed pregnancy that reached beyond 20 weeks' gestation or ended with a birth weight of > 500 g
    • Multiparity: a history of more than one pregnancy that reached beyond 20 weeks' gestation or ended with a birth weight of > 500 g
  • Fetal age [2]
    • Counted as completed weeks of gestation and completed days (0–6) of the current week of pregnancy
    • Gestational age: estimated fetal age (in weeks and days) calculated from the first day of the last menstrual period
    • Conceptional age: the age (in weeks and days) of the fetus calculated from the day of conception (fertilization)
  • Duration of pregnancy
    • Normal duration of pregnancy: 40 weeks (280 days)
    • Postterm pregnancy: a pregnancy that extends beyond 42 weeks' gestation or the estimated date of delivery plus 14 days
    • Periviable birth: live birth occurring between 20–25 weeks of pregnancy
    • Preterm birth: live birth before the completion of 37 weeks (< 37 0/7) of pregnancy
    • Postterm birth: live birth after 42 weeks (> 42 0/7) of pregnancy
  • Trimesters of pregnancy
    • First trimester (weeks 1–13)
    • Second trimester (weeks 14–26)
    • Third trimester (weeks 27–40)

Recording systems

Overview of recording systems
Recording system Description Example
TPAL Obstetric recording system that comprises: term births (T), premature births (P), abortions (A), and living children (L) A woman who reports 5 pregnancies with two miscarriages at weeks 11 and 14 of pregnancy, one medical abortion, one delivery at week 39 of pregnancy of a child weighing 3100 g, one delivery at week 29 of pregnancy of a child weighing 2100 g who died soon after birth should be reported as: T1, P1, A3, L1.
GTPAL An extension of the TPAL recording system that also includes gravidity (G) A woman who reports 5 pregnancies with two miscarriages at weeks 11 and 14 of pregnancy, one medical abortion, one delivery at week 39 of pregnancy of a child weighing 3100 g, one delivery at week 29 of pregnancy of a child weighing 2100 g who died soon after birth should be reported as: G5, T1, P1, A3, L1.
GP Obstetric recording system that comprises: gravidities (G) and parities (P) A woman who reports 4 pregnancies and one delivery of an infant weighing 2100 g at week 32 of pregnancy is reported as: G4, P1.

Presumptive signs

Probable signs [3][4]

Signs Physical findings Weeks of pregnancy
Goodell Cervical softening First 4 weeks
Hegar Softening of the lower segment of the uterus Between 6–8 weeks
Ladin Softening of the midline of the uterus First 6 weeks
Chadwick Bluish discoloration of vagina and cervix Between 6–8 weeks
Telangiectasias and palmar erythema Small blood vessels and redness of the palms First 4 weeks
Chloasma Hyperpigmentation of the face (forehead, cheeks, nose) First 16 weeks

Human chorionic gonadotropin (hCG)

Interpretation of β-hCG findings


β-hCG findings

Low Maternal
High Maternal

Ultrasound findings in normal pregnancy (abdominal or transvaginal) [6]

  • Confirms pregnancy
  • At 5 weeks of pregnancy: detection of the gestational sac (corresponds with a serum β-HCG level of 1500–2000 mIU/mL)
  • At 5–6 weeks of pregnancy: detection of the yolk sac
  • At 6–7 weeks of pregnancy: detection of the fetal pole and cardiac activity with transvaginal ultrasound
  • At 10–12 weeks of pregnancy: detection of fetal heartbeat with doppler ultrasound
  • At 18–20 weeks of pregnancy: fetal movements
  • See POCUS for early pregnancy for more details.

Gestational age and estimated date of delivery

  • Naegele rule: used to calculate the expected date of delivery (due date)
  • Ultrasonography
    • More accurate than Naegele rule
    • Measurement of the crown-rump length (CRL) in the first trimester
    • Measurement of biparietal diameter , fetal femoral length , and abdominal circumference in the second and third trimesters (can be used for determining gestational age starting at 13 weeks) ; ; ; ; [7]
  • Symphysis fundal height: the length from the top of the uterus to the top of the pubic symphysis
    • Used to assess fetal growth and development from approx. 20 weeks' gestation onwards
    • Development is approx. 1 cm/week after 20 weeks
    • Correlates with gestational age

Cardiovascular system [8][9]

A physiological systolic murmur may be heard due to increased cardiac output and increased plasma volume.

Respiratory system [10]

Renal system [9][11]

Endocrine system [9][12][13]

Hematologic system [9][14][15]

Physiological hypercoagulability during pregnancy leads to an increased risk of thrombosis. Patients with thrombophilia should receive adequate thrombosis prophylaxis.

Gastrointestinal system [9]

Musculoskeletal system [9]


Reproductive system

Basic principles

  • Nutritional intake: must be adapted to meet the demands of both the mother and the fetus
  • Dietary recommendations
    • Limit caffeine intake: daily recommended dose < 200 mg (this equals about 1–2 cups of coffee or 2–4 cups of caffeinated tea)
    • Avoid alcohol and tobacco use throughout pregnancy. [16]
    • Avoid unwashed or uncooked foods.
    • Avoid fish with possibly high levels of methylmercury, esp. tilefish, swordfish, shark, mackerel, and tuna.
Recommended vitamin and mineral supplementation in pregnancy [17][18]
Supplementation Reason for increased demand Consequences of deficiency
Folic acid [19]
  • Folic acid 0.4–0.8 mg/day
  • Ideally, women should begin intake 4 weeks prior to pregnancy and continue with this dose for at least the first 2–3 months of pregnancy.
Vitamin B12
  • 2.6 mcg/day
  • Recommended for pregnant women who follow a vegan diet.
Iron [22]
  • 30–60 mg/day
Calcium [23][24]
  • 1,000–1,300 mg/day
  • Increased fetal demand (e.g., for bone development)
  • Lactation
Iodine [26]
  • 250 μg/day
  • Increased metabolism and excretion

Recommended weight-gain during pregnancy [27]

  • Recommended weight-gain is determined by BMI prior to pregnancy
    • BMI < 18.5 (underweight): 28–40 lb (12–18 kg)
    • BMI 18.5–24.9 (normal weight): 25–35 lb (11–16 kg)
    • BMI 25–29.9 (overweight): 15–25 lb (7–11 kg)
    • BMI ≥ 30 (obese): 11–20 lb (5–9 kg)
  • Inadequate gestational weight gain
  • Average recommended daily calorie intake
  • Regular physical activity is recommended (see below).


Safe and unsafe sports during pregnancy [28]

Safe activities High impact training
  • Running, jogging
  • Racquet sports
  • Strength training
Low impact training
  • Swimming
  • Walking
  • Stationary cycling
  • Pilates
  • Yoga

Unsafe activities

  • Contact sports (e.g., soccer, basketball)
  • Activities associated with a high risk of falling (e.g., snow and water skiing, gymnastics, surfing)
  • Activities associated with high risk of dehydration (e.g., hot yoga, hot pilates)
  • Extreme sports (e.g., skydiving, scuba diving)

Physical activity should be discontinued in the event of the following: antepartum or postpartum hemorrhage, uterine contractions, amniotic fluid leakage, chest pain, dyspnea before exertion, dizziness, headaches, calf pain/swelling, and/or muscle weakness with impaired balance.

Early identification of high-risk pregnancies is vital in order to prevent the occurrence of maternal and fetal complications. They require regular prenatal care to monitor and support the pregnant mother (see “Prenatal care”).

Risk factors for a complicated pregnancy [29][30]

Oligohydramnios [33]

Potter babies cannot Pee.

POTTER sequence: Pulmonary hypoplasia (lethal), Oligohydramnios (origin), Twisted facies, Twisted skin, Extremity deformities, and Renal agenesis (classic form).

Polyhydramnios [35]

Other complications

Interested in the newest medical research, distilled down to just one minute? Sign up for the One-Minute Telegram in “Tips and links” below.

  1. Obstetrics Data Definitions. Updated: January 1, 2014. Accessed: August 27, 2020.
  2. Spong CY. Defining “Term” Pregnancy. JAMA. 2013; 309 (23): p.2445. doi: 10.1001/jama.2013.6235 . | Open in Read by QxMD
  3. Anthony J, Osman A, Sani M. Valvular heart disease in pregnancy. Cardiovasc J Afr. 2016; 27 (2): p.111-118. doi: 10.5830/cvja-2016-052 . | Open in Read by QxMD
  4. Soma-Pillay P, Nelson-Piercy C, Tolppanen H, Mebazaa A. Physiological changes in pregnancy. Cardiovasc J Afr. 2016; 27 (2): p.89-94. doi: 10.5830/cvja-2016-021 . | Open in Read by QxMD
  5. LoMauro A, Aliverti A. Respiratory physiology of pregnancy. Breathe. 2015; 11 (4): p.297-301. doi: 10.1183/20734735.008615 . | Open in Read by QxMD
  6. Ghamrawi R, Kattah AG, Garovic VD. Isolated Proteinuria of Pregnancy: A Call for Action. Kidney International Reports. 2019; 4 (6): p.766-768. doi: 10.1016/j.ekir.2019.04.012 . | Open in Read by QxMD
  7. Magon N, Kumar P. Hormones in pregnancy. Nigerian Medical Journal. 2012; 53 (4): p.179. doi: 10.4103/0300-1652.107549 . | Open in Read by QxMD
  8. Cignini P, Cafà EV, Giorlandino C, Capriglione S, Spata A, Dugo N. Thyroid physiology and common diseases in pregnancy: review of literature.. Journal of prenatal medicine. 2012; 6 (4): p.64-71.
  9. Chandra S, Tripathi AK, Mishra S, Amzarul M, Vaish AK. Physiological Changes in Hematological Parameters During Pregnancy. Indian Journal of Hematology and Blood Transfusion. 2012; 28 (3): p.144-146. doi: 10.1007/s12288-012-0175-6 . | Open in Read by QxMD
  10. Bremme KA. Haemostatic changes in pregnancy.. Best Pract Res Clin Haematol. 2003; 16 (2): p.153-168.
  11. Tunzy, Gray. Common Skin Conditions During Pregnancy. American Family Physician. 2007 .
  12. Probable signs of pregnancy. Updated: July 30, 2016. Accessed: September 2, 2020.
  13. Cohen LS. Diagnostic Ultrasound in the First Trimester of Pregnancy. The Global Library of Women's Medicine. 2009 . doi: 10.3843/glowm.10094 . | Open in Read by QxMD
  14. Tezuka et al.. Embryonic Heart Rates: Development in Early First Trimester and Clinical Evaluation. Gynecol Obstet Invest. 1991; 32 (4): p.210-212. doi: 10.1159/000293033 . | Open in Read by QxMD
  15. ISUOG. ISUOG Practice Guidelines: performance of first-trimester fetal ultrasound scan. Ultrasound in Obstetrics & Gynecology. 2012; 41 (1): p.102-113. doi: 10.1002/uog.12342 . | Open in Read by QxMD
  16. Hart TD, Harris MB. Preeclampsia revisited. US Pharm. 2012; 37 (9): p.48-53.
  17. American College of Obstetricians and Gynecologists.. ACOG Committee Opinion No. 764.Medically indicated late-preterm and early-term deliveries.. American Journal of Obstetrics and Gynecology.. 2019 .
  18. Dubil EA, Magann EF. Amniotic fluid as a vital sign for fetal wellbeing. Australasian Journal of Ultrasound in Medicine. 2013; 16 (2): p.62-70. doi: 10.1002/j.2205-0140.2013.tb00167.x . | Open in Read by QxMD
  19. Mousavi AS, Hashemi N, Kashanian M, Sheikhansari N, Bordbar A, Parashi S. Comparison between maternal and neonatal outcome of PPROM in the cases of amniotic fluid index (AFI) of more and less than 5 cm. J Obstet Gynaecol (Lahore). 2018; 38 (5): p.611-615. doi: 10.1080/01443615.2017.1394280 . | Open in Read by QxMD
  20. Salhan S. Textbook of Obstetrics. JP Medical Ltd ; 2016
  21. Taskin S, Pabuccu EG, Kanmaz AG, Kahraman K, Kurtay G. Perinatal outcomes of idiopathic polyhydramnios. Interventional Medicine and Applied Science. 2013; 5 (1): p.21-25. doi: 10.1556/imas.5.2013.1.4 . | Open in Read by QxMD
  22. Sahni M, Ohri A. Meningomyelocele. StatPearls. 2020 .
  23. Hamza A, Herr D, Solomayer E, Meyberg-Solomayer G. Polyhydramnios: Causes, Diagnosis and Therapy. Geburtshilfe Frauenheilkd. 2013; 73 (12): p.1241-1246. doi: 10.1055/s-0033-1360163 . | Open in Read by QxMD
  24. Committee on Obstetric Practice. ACOG Committee Opinion No. 650: Physical Activity and Exercise During Pregnancy and the Postpartum Period. ACOG Comm Opin. 2015 . doi: 10.1097/AOG.0000000000001214 . | Open in Read by QxMD
  25. Galal M, Symonds I, Murray H, Petraglia F, Smith R. Postterm pregnancy.. Facts, views & vision in ObGyn. 2012; 4 (3): p.175-87.
  26. Alkmark M, Keulen JKJ, Kortekaas JC, Bergh C, van Dillen J, Duijnhoven RG, Hagberg H, Mol BW, Molin M, van der Post JAM, Saltvedt S, Wikström AK, Wennerholm UB, de Miranda E. Induction of labour at 41 weeks or expectant management until 42 weeks: A systematic review and an individual participant data meta-analysis of randomised trials.. PLoS medicine. 2020; 17 (12): p.e1003436. doi: 10.1371/journal.pmed.1003436 . | Open in Read by QxMD
  27. Alcohol use in pregnancy. Updated: April 30, 2020. Accessed: August 28, 2020.
  28. Dietary guidelines for Americans 2015-2020. Updated: December 1, 2015. Accessed: August 28, 2020.
  29. Soneji S, Beltrán-Sánchez H. Association of Special Supplemental Nutrition Program for Women, Infants, and Children With Preterm Birth and Infant Mortality. JAMA Network Open. 2019; 2 (12): p.e1916722. doi: 10.1001/jamanetworkopen.2019.16722 . | Open in Read by QxMD
  30. Bibbins-Domingo et al.. Folic Acid Supplementation for the Prevention of Neural Tube Defects. JAMA. 2017; 317 (2): p.183-189. doi: 10.1001/jama.2016.19438 . | Open in Read by QxMD
  31. Viswanathan M, Treiman KA, Kish-Doto J, Middleton JC, Coker-Schwimmer EJ, Nicholson WK. Folic Acid Supplementation for the Prevention of Neural Tube Defects: An Updated Evidence Report and Systematic Review for the US Preventive Services Task Force.. JAMA. 2017; 317 (2): p.190-203. doi: 10.1001/jama.2016.19193 . | Open in Read by QxMD
  32. McNulty B, McNulty H, Marshall B, et al. Impact of continuing folic acid after the first trimester of pregnancy: findings of a randomized trial of Folic Acid Supplementation in the Second and Third Trimesters.. Am J Clin Nutr. 2013; 98 (1): p.92-8. doi: 10.3945/ajcn.112.057489 . | Open in Read by QxMD
  33. Cantor et al.. Routine Iron Supplementation and Screening for Iron Deficiency Anemia in Pregnancy: A Systematic Review for the U.S. Preventive Services Task Force. Ann Intern Med. 2015; 162 (8): p.566. doi: 10.7326/m14-2932 . | Open in Read by QxMD
  34. Calcium. . Accessed: June 6, 2019.
  35. Mahadevan S, Kumaravel V, Bharath R. Calcium and bone disorders in pregnancy. Indian J Endocrinol Metab. 2012; 16 (3): p.358–363. doi: 10.4103/2230-8210.95665 . | Open in Read by QxMD
  36. Calcium and bone disorders in pregnancy..
  37. Stagnaro-Green A et al. Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum. Thyroid. 2011; 21 (10): p.1081-1125. doi: 10.1089/thy.2011.0087 . | Open in Read by QxMD
  38. Weight gain during pregnancy. Updated: January 17, 2019. Accessed: August 28, 2020.
  39. Ferri FF. Ferri's Clinical Advisor 2017. Elsevier ; 2016 : p. 1345-1346
  40. Callahan TL, Caughey AB. Blueprints Obstetrics and Gynecology. Lippincott Williams&Wilki ; 2013
  41. Medical Embryology, the Placenta: Decidual Formation.
  42. Smith JA, Refuerzo JS, Ramin SM, Lockwood CJ, Barss VA. Treatment and Outcome of Nausea and Vomiting of Pregnancy. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: January 3, 2017. Accessed: June 16, 2017.
  43. Ehsanipoor RM, Satin AJ, Lockwood CJ, Barss VA. Normal and Abnormal Labor Progression. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: June 7, 2017. Accessed: June 16, 2017.
  44. Refuerzo JS, Smith JA, Ramin SM, Lockwood CL, Barss VA. Clinical Features and Evaluation of Nausea and Vomiting of Pregnancy. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: January 3, 2017. Accessed: July 7, 2017.
  45. American College of Obstetricians and Gynecologists. Practice Bulletin No. 142: Cerclage for the Management of Cervical Insufficiency. Obstet Gynecol. 2014; 123 (2): p.372-379. doi: 10.1097/ . | Open in Read by QxMD
  46. Ressel GW. ACOG Releases Bulletin on Managing Cervical Insufficiency. Am Fam Physician. 2004; 69 (2): p.436-439.
  47. Norwitz ER, Saade GA, Miller HS, Davidson CM. Obstetric Clinical Algorithms. Wiley-Blackwell ; 2016
  48. Berghella V, Lockwood CJ, Barss VA. Cervical Insufficiency. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: January 4, 2017. Accessed: July 7, 2017.
  49. Tao Le, Vikas Bhushan, Deol M, Reyes G. First Aid for the USMLE Step 2 CK, Tenth Edition. McGraw-Hill Education ; 2018
  50. Ciobanu et al.. Thrombocytopenia in Pregnancy. Maedica. 2016; 11 (1): p.55-60.
  51. Reese JA, Peck JD, Deschamps DR, et al. Platelet Counts during Pregnancy. N Engl J Med. 2018; 379 (1): p.32-43. doi: 10.1056/nejmoa1802897 . | Open in Read by QxMD
  52. Valenti O, Di Prima FA, Renda E, et al. Fetal cardiac function during the first trimester of pregnancy.. Journal of prenatal medicine. 2011; 5 (3): p.59-62.

3 free articles remaining

You have 3 free member-only articles left this month. Sign up and get unlimited access.
 Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer