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 “” and “ .”
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 
- 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)
|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 |
|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)
- Site of production: placental syncytiotrophoblast
- Pregnancy test: measurement of human chorionic gonadotropin (β-hCG)
Ultrasound findings in normal pregnancy (abdominal or transvaginal) 
- 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 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 for more details.
Gestational age and estimated date of delivery
- Naegele rule: used to calculate the expected date of delivery (due date)
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 
- ↑ Progesterone → ↓ vascular tone → ↓ peripheral vascular resistance (↓ afterload)
- Innocent systolic murmur
- The apex beat is displaced upward.
- ↑ Plasma volume → ↓ oncotic pressure → edema of lower limbs
- Aggravation of preexisting valvular diseases
Respiratory system 
- ↑ Oxygen consumption (by approx. 20%)
- ↑ Intraabdominal pressure through uterine growth → dyspnea (the diaphragm is displaced upwards → ↓ total lung capacity, residual volume, functional residual capacity, and expiratory reserve volume)
- Progesterone stimulates the respiratory centers in the brain → hyperventilation (to eliminate fetal CO2 more efficiently) → physiological, chronic compensated respiratory alkalosis
Renal system 
- ↑ Renal plasma flow → ↑ GFR → ↓ BUN and creatinine
- ↑ Aldosterone → ↑ plasma volume and hypernatremia
- ↑ Progesterone and intraabdominal pressure → dilation of kidney, pelvis, and calyceal systems → reduced tone and peristalsis
- ↑ Glucose levels in urine: Increased glomerular filtration results in overload of the glucose carrier responsible for its resorption.
- Mild proteinuria: Increased GFR and glomerular permeability to albumin increases protein excretion.
Endocrine system 
- Human placental lactogen: a hormone synthesized by syncytiotrophoblasts of the placenta, which promotes the production of insulin-like growth factors.
- Thyroid hormones
- ↑ SHBG and corticosteroid-binding globulin
- ↑ Triglycerides and cholesterol (due to increased lipolysis and fat utilization)
- Hyperplasia of lactotroph cells in the anterior pituitary → physiological enlargement of the pituitary gland (up to 40% increase from pregestational volume)
Hematologic system 
- ↑ Plasma volume → ↓ hematocrit, especially towards the end of pregnancy (30–34th week of gestation) → dilutional anemia (hemoglobin value rarely drops below 11 g/dL)
- ↑ RBC mass (increases from 8–10th week of gestation until the end of pregnancy)
- ↓ Platelet count 
- ↑ WBC count
- ↓ Albumin
- Hypercoagulability is due to an increase in fibrinogen, factor VII, and factor VIII and a decrease in protein S; (reduces the risk of intrapartum blood loss).
- ↑ Alkaline phosphatase (placental isoenzymes)
- ↓ Iron and folate levels due to increased vitamin and mineral requirements
Gastrointestinal system 
- ↑ Salivation
- ↓ Lower esophageal sphincter tone → gastroesophageal reflux
- ↓ Motility → constipation
- Gallbladder stasis → gallstones
Pelvic girdle pain 
- Etiology: increased pressure from the uterus, lumbar lordosis, and relaxation of the ligaments supporting the joints of the pelvic girdle
- Clinical features: lower back pain
- Diagnosis: positive pelvic pain provocation tests (e.g., , , )
Round ligament pain
- Etiology: stretching of the as the uterus expands
- Epidemiology: one of the most common conditions during pregnancy
- Clinical features
- Diagnosis: based on clinical history
- Management: usually no treatment required; resolves after delivery
- Spider angioma
- Palmar erythema
- Striae gravidarum: scarring that manifests as erythematous, violaceous, and/or hypopigmented linear striations on the abdomen
- Hyperpigmentation: chloasma, linea nigra, hyperpigmentation of the nipples
- Nutritional intake: must be adapted to meet the demands of both the mother and the fetus
- 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. 
- Avoid unwashed or uncooked foods.
- Fish (contamination with parasites and bacteria)
- Milk products: high risk of
- Meat: high risk of
- Avoid fish with possibly high levels of methylmercury, esp. tilefish, swordfish, shark, mackerel, and tuna.
|Recommended vitamin and mineral supplementation in pregnancy |
|Supplementation||Reason for increased demand||Consequences of deficiency|
|Folic acid || |
|Vitamin B12|| || || |
|Iron || || |
|Calcium || || |
|Iodine || || || |
Recommended weight-gain during pregnancy 
- Recommended weight-gain is determined by BMI prior to pregnancy
- Average recommended daily calorie intake
- Regular physical activity is recommended (see below).
- Regular physical activity (e.g., aerobic and strength-training exercise) is considered beneficial and is recommended before, during, and after pregnancy.
- Careful evaluation of medical and obstetric disorders is necessary before recommending regular physical activity.
- Contraindications to aerobic exercise
- Exercise routines that are considered unsafe during pregnancy should be avoided or modified accordingly.
|Safe and unsafe sports during pregnancy |
|Safe activities|| |
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 “ ”).
Risk factors for a complicated pregnancy 
- Family history (medical and obstetric) of complicated pregnancies
- Personal history
- Advanced maternal age (> 35 years)
- First pregnancy
- Multiparity (> 5 births)
- Medical conditions (e.g., epilepsy, malignancies) , , ,
- Social and environmental factors (e.g., drug use, stress)
- Preexisting gynecological conditions (e.g., uterine leiomyoma, history of uterine surgery)
- Prior complicated pregnancies
- Complications that arise during pregnancy: See “ ” and section below.
- Definition: amount of amniotic fluid is less than expected for gestational age
- Small abdominal girth and uterine size for gestational age
- Ultrasound: determine amniotic fluid and assess for fetal anomalies
Amniotic fluid index (AFI): a semiquantitative tool used to assess amniotic fluid volume (normal range: 8–18 cm)
- Determined by dividing the uterus into 4 quadrants, holding the transducer perpendicular to the patient's spine, and adding up the deepest vertical pocket of fluid in each quadrant.
- Oligohydramnios: ≤ 5
- In pregnancies < 24 weeks and multiple gestations, the single deepest pocket is used (normal range: 2–8 cm).
- Intrauterine growth restriction (due to diminished mobility of the fetus)
- Birth complications (e.g., umbilical cord compression)
- Pathophysiology: oligohydramnios → intrauterine compression and decreased amniotic fluid ingestions → ↓ space for fetal development → internal and external deformations
- Clinical features
Potter babies cannot Pee.
- Definition: excessive amniotic fluid volume expected for gestational age that results in uterine distention.
- Typically idiopathic (∼ 70% of cases) 
- Gastrointestinal (e.g., : , )reduced swallowing and absorption of amniotic fluid
- CNS: ; (leads to impaired swallowing of amniotic fluid, leakage of cerebrospinal fluid, and increased urination due to lack of fetal ADH), (due to leakage of cerebrospinal fluid) 
- Pulmonary: cystic lung malformations
- Multiple pregnancy: twin-to-twin transfusion syndrome
- Fetal anemia 
- Intrauterine infections (e.g., )
- Maternal conditions