Pregnancy is a period of profound physiological change, typically lasting 40 weeks (38 weeks from conception). Prenatal care aims to optimize maternal and fetal health through regular monitoring, screening, preventive interventions, and management of complications.
Prenatal Care Schedule
The standard prenatal visit schedule: confirmation visit (8-12 weeks), monthly visits (weeks 12-28), every 2 weeks (weeks 28-36), and weekly (weeks 36-40+). First visit includes complete history and physical, dating ultrasound, prenatal labs (CBC, blood type and Rh, antibody screen, rubella titer, syphilis, HIV, hepatitis B, gonorrhea/chlamydia, Pap smear, urinalysis, and cystic fibrosis carrier screening). Genetic screening is offered based on maternal age and risk.
Subsequent visits include weight, blood pressure, fundal height measurement (after 20 weeks), fetal heart rate auscultation, urine dipstick (glucose, protein), and symptom review. Screening tests: first-trimester nuchal translucency ultrasound and maternal serum screen (11-14 weeks), quad screen or cell-free fetal DNA (15-20 weeks), fetal anatomy ultrasound (18-22 weeks), glucose tolerance test for gestational diabetes (24-28 weeks), and group B streptococcus screening (35-37 weeks).
Physiological Changes of Pregnancy
Cardiovascular changes include increased blood volume (40-50%), increased cardiac output (30-50%), decreased systemic vascular resistance, physiologic anemia (plasma volume increases more than red cell mass), and mild decrease in blood pressure (especially second trimester). Respiratory changes include increased tidal volume (30-40%), increased minute ventilation (50%), decreased functional residual capacity, and respiratory alkalosis (compensated). Renal changes include increased renal blood flow and GFR (50%), glycosuria (not diagnostic of diabetes), and increased urinary frequency. Gastrointestinal changes include delayed gastric emptying, relaxed lower esophageal sphincter (heartburn), and slowed bowel motility (constipation). Musculoskeletal changes include relaxed ligaments (due to relaxin), lordosis, and widened pubic symphysis. Hormonal changes include high hCG (from placenta — maintains corpus luteum in first trimester), high estrogen and progesterone, increased prolactin, and insulin resistance (mediated by human placental lactogen).
Common Pregnancy Symptoms
Nausea and vomiting (50-80%, typically weeks 6-14) — management: dietary changes (small frequent meals, avoid triggers, ginger, vitamin B6 25 mg q6h + doxylamine 12.5 mg at bedtime). Heartburn (30-50%) — antacids, avoid lying down after meals. Constipation — increased fiber and hydration, stool softeners. Back pain — posture, exercise, support belts. Braxton Hicks contractions — irregular, painless uterine contractions (increased in third trimester). Fatigue (first and third trimesters). Urinary frequency. Edema (dependent, mild). Varicose veins.
Complications of Pregnancy
Gestational diabetes (6-9% of pregnancies) — glucose intolerance with onset in pregnancy. Diagnosed by 1-hour 50 g glucose challenge test (over 130-140 mg/dL screen positive, followed by 3-hour 100 g OGTT). Treatment: medical nutrition therapy, glucose monitoring, insulin or metformin (if not controlled with diet). Risk of fetal macrosomia, neonatal hypoglycemia, and increased cesarean delivery. Most resolves after delivery, but lifetime diabetes risk is 50% higher.
Hypertensive disorders of pregnancy include gestational hypertension (BP over 140/90 without proteinuria, after 20 weeks), preeclampsia (BP over 140/90 + proteinuria — can progress to severe: BP over 160/110, headache, visual changes, RUQ pain, thrombocytopenia, hepatic dysfunction, pulmonary edema), and eclampsia (preeclampsia + seizures). Risk factors: first pregnancy, multiple gestation, prior preeclampsia, obesity, chronic hypertension, diabetes, and family history. Prevention: low-dose aspirin (81 mg) starting at 12 weeks in high-risk women. Treatment: delivery is the only cure; management includes antihypertensives (labetalol, nifedipine, hydralazine) and magnesium sulfate for seizure prophylaxis (in severe preeclampsia).
Preterm labor (regular contractions with cervical change before 37 weeks). Risk factors include prior preterm birth, multiple gestation, infections, smoking, and short cervical length. Diagnosis: transvaginal cervical length under 20 mm or positive fetal fibronectin test. Acute management: tocolytics (nifedipine, indomethacin, terbutaline) for 48 hours to allow betamethasone administration for fetal lung maturity. Maintenance tocolysis is not generally recommended. Vaginal progesterone reduces preterm birth risk in women with short cervix (under 25 mm).
Placenta previa (placenta covering the cervical os) presents as painless vaginal bleeding in the second or third trimester. Diagnosis: ultrasound. Management: pelvic rest, avoidance of intercourse and vaginal exams, and cesarean delivery. Placental abruption (premature separation of the placenta) presents as painful vaginal bleeding and abdominal pain — a true emergency.
Nutrition and Exercise in Pregnancy
Increased caloric needs: approximately 300-450 additional calories per day in the second and third trimesters. Weight gain recommendations depend on pre-pregnancy BMI: underweight (BMI < 18.5) — 28-40 lbs, normal (18.5-24.9) — 25-35 lbs, overweight (25-29.9) — 15-25 lbs, obese (over 30) — 11-20 lbs. Folic acid 400-800 mcg/day (4,000 mcg with prior neural tube defect) prevents neural tube defects. Iron supplementation (27 mg/day elemental iron in prenatal vitamin — some women require additional iron for anemia). Calcium (1,000 mg/day). Vitamin D (600 IU/day). Avoid: alcohol, tobacco, illicit drugs, raw/undercooked meat and fish (toxoplasmosis, listeriosis), high-mercury fish (shark, swordfish, king mackerel, tilefish — limit tuna to 6 oz/week), and excessive caffeine (limit to 200 mg/day — 1-2 cups of coffee). Exercise: 150 minutes of moderate activity per week is recommended — walking, swimming, stationary cycling, and prenatal yoga are safe.
Summary
Pregnancy involves profound physiological changes across all organ systems. Prenatal care follows a scheduled pattern of visits and screening tests. Common complications include gestational diabetes, hypertensive disorders (preeclampsia), preterm labor, and placental abnormalities. Preeclampsia requires urgent delivery. Nutrition, folic acid, appropriate weight gain, and moderate exercise support healthy pregnancy outcomes. The goal of prenatal care is a healthy mother and baby.