Pregnancy

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. 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).

Management of pregnancy, including counseling, examinations, ultrasound, and care of high-risk pregnancies, is covered separately in the article “Prenatal care.”

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)
  • Late-term pregnancy: a pregnancy between 41 0/7 and 41 6/7 weeks' gestation
  • Postterm pregnancy: a pregnancy that extends beyond ≥ 42 0/7 weeks' gestation or the estimated date of delivery plus 14 days
• Gestional age at birth
  • Periviable birth: live birth occurring between 20–25 weeks' gestation
  • Preterm birth: live birth before the completion of 37 weeks of gestation (< 37 0/7 weeks' gestation)
  • Postterm birth: live birth after the completion of 42 weeks of gestation (≥ 42 0/7 weeks' gestation)
• Trimesters of pregnancy
  • First trimester (weeks 1–13)
  • Second trimester (weeks 14–26)
  • Third trimester (weeks 27–40)

Recording systems

Presumptive signs

• Amenorrhea
• Nausea and vomiting
• Breast enlargement and tenderness
• Linea nigra: darkening of the midline skin of the abdomen
• Hyperpigmentation of the areola
• Abdominal bloating and constipation
• Increased weight gain
• Cravings for or aversions to certain foods
• Increased urinary frequency
• Fatigue

Probable signs ^[3][4]

Human chorionic gonadotropin (hCG)

• Site of production: placental syncytiotrophoblast
• Structure
  • α-subunit: common to hCG, FSH, LH, and TSH
  • β-subunit: specific to the placenta (pregnancy tests measure the β-hCG levels)
• Function
  • Maintenance of the corpus luteum during the first 8–10 weeks of pregnancy (LH has a similar function)
  • Luteal-placental shift: levels decrease after corpus luteum involution (placenta starts synthesizing its own estriol and progesterone)
• Pregnancy test: measurement of human chorionic gonadotropin (β-hCG)
  • Urine β-hCG test (e.g., home pregnancy test)
    • Qualitative test (less sensitive than serum pregnancy test)
    • β-hCG can be detected in urine 14 days after fertilization
  • Serum β-hCG test
    • Quantitative test (high sensitivity)
    • Detectable 6–9 days (on average) after fertilization

Interpretation of β-hCG findings

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

See also “Prenatal ultrasound” and “Gestational age and estimated date of delivery.”

• 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.

Cardiovascular system ^[7][8]

• ↑ Progesterone → ↓ vascular tone → ↓ peripheral vascular resistance (↓ afterload)
  • ↑ Cardiac output by up to 40% (↑ preload)
  • ↑ Stroke volume (by 10–30%)
  • ↑ Heart rate (by ∼ 12–18 bpm) → ↑ uterine perfusion
  • ↓ Mean arterial pressure
• Innocent systolic murmur
• The apex beat is displaced upward.
• ↑ Plasma volume → ↓ oncotic pressure → edema of lower limbs
• Varicosities
• Aggravation of preexisting valvular diseases

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

Respiratory system ^[9]

• ↑ 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
  • ↑ Tidal volume → ↑ minute ventilation
  • ↓ PCO₂ (∼ 30 mm Hg)

Renal system ^[8][10]

• ↑ 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
  • Hydronephrosis and hydroureter
  • Hypomotility of the ureters → urinary stasis → pyelonephritis
• ↑ Urinary frequency
• ↑ 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 ^[8][11][12]

• Progesterone
  • Responsible for pregnancy maintenance
  • Produced by the corpus luteum until the 10–12 weeks of gestation, after which it is produced by the fetoplacental unit
• Human placental lactogen: a hormone synthesized by syncytiotrophoblasts of the placenta, which promotes the production of insulin-like growth factors.
  • Increases insulin levels
  • Causes insulin resistance
  • Increases serum glucose levels and lipolysis to ensure sufficient glucose supply for the fetus
  • Maternal insulin resistance begins in the second trimester and peaks in the third trimester.
• Thyroid hormones
  • ↑ hCG → ↓ TSH levels during the first part of the first trimester
  • ↑ TBG → ↑ T₄ and T₃ → slightly increased free T₄ and T₃ levels during first trimester
  • Free T4 and T3 levels decrease during the second and third trimesters
• ↑ 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 ^[8][13][14]

• ↑ Plasma volume → ↓ hematocrit, especially towards the end of pregnancy (30–34^th week of gestation) → dilutional anemia (hemoglobin value rarely drops below 11 g/dL)
• 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).
• ↓ Platelet count → gestational thrombocytopenia
• ↑ RBC mass (increases from 8–10^th week of gestation until the end of pregnancy)
• ↓ Iron and folate levels due to increased vitamin and mineral requirements
• ↑ WBC count
• ↓ Albumin
• ↑ Alkaline phosphatase (placental isoenzymes)

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

Gastrointestinal system ^[8]

• ↑ Salivation
• ↓ Lower esophageal sphincter tone → gastroesophageal reflux
• ↓ Motility → constipation and bloating
• Gallbladder stasis → gallstones
• Hemorrhoids

Musculoskeletal system ^[8]

• ↑ Body weight → forward shift in center of gravity → ↑ lumbar lordosis
• ↑ Intraabdominal pressure → diastasis recti; meralgia paresthetica
• Relaxation of the pelvic girdle ligaments and symphysis pubis; → pelvic girdle pain, coccygeal pain
• Fluid retention in tissue → carpal tunnel syndrome

Skin

• 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

Reproductive system

• Uterus: increase in size
• Vulva and vagina
  • Vaginal discharge
  • Formation of varicose veins
• Mammary glands: increase in size; breast fullness and tenderness

Oligohydramnios ^[15]

• Definition: amount of amniotic fluid is less than expected for gestational age
• Etiology
  • Fetal anomalies
    • Urethral obstruction (e.g., posterior urethral valves)
    • Bilateral renal agenesis
    • Autosomal recessive polycystic kidney disease (ARPKD)
    • Chromosomal aberrations (e.g., trisomy 18)
    • Intrauterine infections (e.g., congenital TORCH infections)
    • In multiple pregnancies: twin-to-twin transfusion syndrome
  • Maternal conditions
    • Placental insufficiency
    • Late or postterm pregnancies (> 42 weeks of gestation)
    • Premature rupture of membranes
    • Preeclampsia
  • Idiopathic
• Diagnosis ^[16]
  • 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).
• Treatment
  • Amnioinfusion: infusion of fluid into the amniotic cavity through amniocentesis
  • Treat underlying cause: See “Preeclampsia,” “Premature rupture of membranes,” and “Placental insufficiency.”
  • Delivery is advised if the fetus is close to term.
• Complications
  • Intrauterine growth restriction (due to diminished mobility of the fetus)
  • Birth complications (e.g., umbilical cord compression)
  • Potter sequence
    • Etiology
      • Chronic placental insufficiency
      • ↓ Renal output (e.g., due to bilateral renal agenesis, ARPKD, obstruction of posterior urethral valves)
      • Chronic amniotic fluid leakage
    • Pathophysiology: oligohydramnios → intrauterine compression and decreased amniotic fluid ingestions → ↓ space for fetal development → internal and external deformations
    • Clinical features
      • Pulmonary hypoplasia (cause of death due to severe neonatal respiratory insufficiency)
      • Craniofacial abnormalities (e.g., prominent epicanthal and infraorbital folds, flattened nose, receding chin, low set ears)
      • Wrinkling of the skin
      • Limb anomalies (e.g., bowed legs, clubbed feet)

Potter babies cannot Pee.

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

Polyhydramnios ^[17]

• Definition: excessive amniotic fluid volume expected for gestational age that results in uterine distention.
• Etiology
  • Typically idiopathic (∼ 70% of cases) ^[18]
  • Fetal anomalies
    • Gastrointestinal (e.g., esophageal atresia, duodenal atresia and stenosis): reduced swallowing and absorption of amniotic fluid
    • CNS: anencephaly; (leads to impaired swallowing of amniotic fluid, leakage of cerebrospinal fluid, and increased urination due to lack of fetal ADH), meningomyelocele (due to leakage of cerebrospinal fluid) ^[19]
    • Pulmonary: cystic lung malformations
    • Multiple pregnancy: twin-to-twin transfusion syndrome
    • Fetal anemia ^[20]
    • Chromosomal aberrations
    • Intrauterine infections (e.g., congenital TORCH infections)
  • Maternal conditions
    • Diabetes mellitus
    • Rh incompatibility (e.g., hemolytic disease of the newborn)
• Diagnostics
  • Physical examination: abdominal girth and uterine size large for gestational age
  • Ultrasound
    • AFI ≥ 25
    • Assess for fetal anomalies
  • Others
    • Rh screen
    • Blood glucose
• Management
  • All patients should obtain regular biophysical profile with nonstress test
  • Amnioreduction: drainage of excess amniotic fluid
    • Indications: severe abdominal discomfort, uterine irritability, severe shortness of breath
    • Complications: preterm labor, premature rupture of membranes
  • Treatment of underlying cause (e.g., glycemic control in diabetic mothers, intrauterine exchange transfusion in hemolytic disease of the newborn)
• Complications
  • Fetal malposition
  • Umbilical cord prolapse
  • Premature birth
  • Premature rupture of membranes
  • Premature uterine contractions

Other complications

• Hemolytic disease of the fetus and newborn
• Intrauterine growth restriction
• Teratogenic birth defects

• One-Minute Telegram 9-2020-2/3: COVID-19: Pregnant women at increased risk for complications

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