10.1 Antepartum Care & Pregnancy Complications

Antepartum Care & Pregnancy Complications: Clinical Management and Algorithms

Quick Answer: Antepartum care prioritizes risk assessment and routine screening timelines—know when to screen for gestational diabetes (24–28 weeks) and GBS (36–37 weeks). Differentiate painless third-trimester bleeding (placenta previa, vasa previa) from painful bleeding (placental abruption), and never perform digital exams before ultrasound. Manage preeclampsia based on severe features and gestational age, utilizing magnesium sulfate for seizure prophylaxis.

Routine Prenatal Screening and Care

Prenatal management begins with establishing accurate gestational age, ideally by first-trimester crown-rump length ultrasound.

Chronological Prenatal Screening Timeline

Managing a normal pregnancy requires adherence to a strict timeline of screening and diagnostic tests:

• Initial Prenatal Visit:
  • Confirm gestational age via ultrasound (crown-rump length is most accurate in the first trimester).
  • Obtain baseline lab work: CBC, blood type and Rh factor, antibody screen, rubella and varicella immunity, and infectious serologies (HIV, RPR/VDRL for syphilis, HBsAg for hepatitis B, chlamydia screening).
• 10 to 13 Weeks: Fetal aneuploidy screening via cell-free DNA (NIPS, starting at 10 weeks) or first-trimester combined screening (PAPP-A, free beta-hCG, and nuchal translucency).
• 12 to 16 Weeks: Screen for asymptomatic bacteriuria with a routine urine culture.
• 15 to 22 Weeks: Quadruple screening (AFP, beta-hCG, estriol, inhibin A) if desired.
• 18 to 22 Weeks: Fetal anatomy ultrasound.
• 24 to 28 Weeks: Gestational diabetes mellitus (GDM) screening with a 1-hour 50g oral glucose challenge test (followed by a diagnostic 3-hour 100g oral glucose tolerance test if positive).
• 28 Weeks: Administer Rho(D) immune globulin to unsensitized Rh-negative mothers.
• 36 to 37 Weeks: Rectovaginal culture for Group B Streptococcus (GBS) colonization.

Hypertensive Disorders of Pregnancy

Hypertensive disorders are diagnosed after 20 weeks gestation. Gestational hypertension is BP ≥140/90 mmHg on two occasions at least 4 hours apart without proteinuria or systemic signs. Preeclampsia requires BP ≥140/90 mmHg plus proteinuria (≥300 mg/24h or protein/creatinine ratio ≥0.3). In the absence of proteinuria, preeclampsia is diagnosed with new-onset hypertension plus severe features: thrombocytopenia (<100,000/mcL), renal insufficiency (creatinine >1.1 mg/dL or doubling), impaired liver function (AST/ALT twice normal or severe persistent right upper quadrant pain), pulmonary edema, or new-onset cerebral/visual disturbances. Preeclampsia with severe features includes these findings or BP ≥160/110 mmHg. A severe variant, HELLP syndrome, presents with hemolysis (schistocytes on smear, elevated bilirubin, LDH >600 U/L), elevated liver enzymes, and low platelets. High-risk patients should start low-dose aspirin at 12–28 weeks to prevent preeclampsia. Deliver preeclampsia without severe features at 37 0/7 weeks, and with severe features at 34 0/7 weeks (or immediately if unstable). Administer intravenous magnesium sulfate for seizure prophylaxis during labor and 24 hours postpartum. Monitor for magnesium toxicity: loss of deep tendon reflexes (7-10 mEq/L), respiratory depression (11-15 mEq/L), and cardiac arrest. Treat toxicity with IV calcium gluconate. Severe hypertension (BP ≥160/110 mmHg) requires IV labetalol, IV hydralazine, or oral nifedipine. Avoid ACE inhibitors and ARBs due to fetal renal toxicity. Eclampsia (tonic-clonic seizures) requires magnesium sulfate, blood pressure control, and prompt delivery.

Gestational Diabetes Mellitus (GDM)

Gestational diabetes is driven by placental secretion of human placental lactogen (hPL), which increases maternal insulin resistance to ensure adequate glucose supply to the fetus. Diagnose GDM using the 3-hour OGTT if two or more values are met: fasting ≥95, 1-hour ≥180, 2-hour ≥155, and 3-hour ≥140 mg/dL. First-line management consists of nutritional therapy and exercise, with blood glucose checks fasting (<95 mg/dL) and 1-hour (<140 mg/dL) or 2-hour (<120 mg/dL) postprandial. Initiate pharmacotherapy if diet fails. Insulin is the first-line medication as it does not cross the placenta. Oral agents like metformin and glyburide are second-line; metformin crosses the placenta, and glyburide increases risks of macrosomia and neonatal hypoglycemia. Poorly controlled GDM increases risks of fetal macrosomia, shoulder dystocia, respiratory distress syndrome, and neonatal hypoglycemia (caused by fetal hyperinsulinemia in response to maternal hyperglycemia). Deliver well-controlled diet-managed GDM at 39 0/7 to 40 6/7 weeks, and medication-managed GDM at 39 0/7 to 39 6/7 weeks. Screen patients postpartum with a 2-hour 75g OGTT at 4–12 weeks to assess for Type 2 diabetes.

Third-Trimester Bleeding

Obstetric bleeding in the third trimester requires immediate evaluation. Placenta previa (placenta covering the internal os) presents as sudden, painless vaginal bleeding. Risk factors include prior Cesarean section, multiparity, and smoking. Never perform a digital vaginal exam until previa is ruled out by transvaginal ultrasound, as digital palpation can cause severe maternal hemorrhage. Manage stable previa with pelvic rest and scheduled Cesarean delivery at 36 0/7 to 37 6/7 weeks. Placental abruption (premature separation of the placenta) presents as painful vaginal bleeding, severe abdominal pain, uterine tenderness, and high-frequency contractions. Risk factors include hypertension, cocaine use, smoking, and abdominal trauma. Management involves IV fluids, continuous fetal monitoring, and delivery (vaginal if stable, emergent Cesarean if maternal or fetal instability). Vasa previa (fetal vessels crossing the internal os) presents as painless bleeding and fetal bradycardia immediately after rupture of membranes. It requires scheduled Cesarean at 34 0/7 to 35 6/7 weeks to prevent fetal exsanguination. Uterine rupture occurs mainly in patients with prior uterine scars and presents with sudden abdominal pain, loss of fetal station, and fetal distress, requiring emergent laparotomy. Hemodynamic stability must be prioritized, including preparing for massive transfusion protocols if blood loss is severe.