Prenatal care

Gestational Age (GA) & Estimated Date of Delivery (EDD)

• Gestational Age (GA): Time elapsed since the first day of the Last Menstrual Period (LMP). It is measured in weeks and is the standard way to date a pregnancy. Note that GA is about two weeks longer than the fetal age (time since conception).
• Estimated Date of Delivery (EDD): Calculated as 40 weeks (280 days) from the first day of the LMP.

Methods for Determining GA and EDD

• Naegele’s Rule: A common method to estimate the EDD, assuming a 28-day cycle.
  • Calculation: (LMP - 3 months) + 7 days + 1 year.
  • Example: If LMP is 11/1/2023, EDD is 8/8/2024.
• Ultrasound: The most accurate method for determining GA, especially in the first trimester (up to 13 weeks and 6 days). It is particularly useful if the LMP is uncertain or cycles are irregular.

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Fundal Height

• Definition: The distance in centimeters from the pubic symphysis to the top of the uterine fundus. It’s a non-invasive screening tool to assess fetal growth.
• Measurement:
  • Typically starts being measured around 20-24 weeks of gestation.
  • The patient should lie supine, and a tape measure is used for the measurement. An empty bladder is preferred as a full one can alter the measurement.

Correlation with Gestational Age

• From 20-36 weeks: Fundal height in cm should roughly equal the GA in weeks (± 2 cm).
  • Example: At 28 weeks GA, the fundal height is expected to be around 26-30 cm.
• Key Landmarks:
  • 12 weeks: Uterine fundus at the level of the pubic symphysis.
  • 16 weeks: Halfway between the pubic symphysis and the umbilicus.
  • 20 weeks: At the umbilicus.
  • 36 weeks: Reaches the xiphoid process (highest point).
  • >36 weeks: Fundal height may decrease as the fetal head engages in the pelvis (“lightening”).

Tip

先记住三个 12周 耻骨联合上2－3横指(常考) 28周 脐以上3横指 36周 剑突下2横指 然后以4周2个横指推算 24周就脐上1横指 20周就脐下1横指 16周未具体说明 在脐与耻骨联合之间 32周未具体说明 在脐与剑突直接 40周 因为38周羊水达到最大量1000ml 40周大概只有800ml 所以宫底可以在剑突下或者略高于剑突

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Clinical Significance of Discrepancies

• A discrepancy of > 2-3 cm from the expected GA warrants further investigation, usually with an ultrasound.
• Fundal Height > GA (Large for Gestational Age - LGA):
  • Fetal macrosomia (often due to maternal diabetes).
  • Multiple gestations (e.g., twins).
  • Polyhydramnios (excess amniotic fluid).
  • Uterine fibroids.
  • Incorrect dating of pregnancy.
  • Maternal obesity can lead to less accurate measurements.
  • Breech presentation.
• Fundal Height < GA (Small for Gestational Age - SGA):
  • Intrauterine Growth Restriction (IUGR).
  • Oligohydramnios (low amniotic fluid).
  • Incorrect dating of pregnancy.
  • Fetal descent into the pelvis.
  • Small maternal stature or strong abdominal muscles.
  • Transverse lie.

Physical activity during pregnancy

• ACOG Recommendation: ≥150 min/week of moderate aerobic exercise.
• Key Benefits: ↓ GDM, ↓ preeclampsia, ↓ C-section rates, ↓ macrosomia (>4000g).
• Absolute Contraindications:
  • Cervical insufficiency / cerclage. c
  • Placenta previa (>20 wks), PPROM, or acute preterm labor.
  • Severe preeclampsia or persistent 2nd/3rd trimester bleeding.
  • Severe cardiac (e.g., aortic stenosis) or restrictive lung disease.
• Unsafe Activities & High-Yield Hazards:
  • Contact sports (soccer, martial arts) → Placental abruption.
  • Scuba diving → Fetal decompression sickness.
  • Hot yoga/pilates → Maternal hyperthermia → Neural Tube Defects (NTDs) in 1st trim.
  • Supine exercise post-1st trimester → IVC compression (aortocaval compression) → ↓ venous return → maternal hypotension & fetal hypoxia.
  • High fall-risk activities (downhill skiing, horseback riding).
• Safe Activities: Walking, swimming, stationary cycling, prenatal yoga (modified), low-impact aerobics.
• Red-Flag Symptoms to Stop Exercise:
  • Vaginal bleeding or fluid leakage (PROM).
  • Regular, painful uterine contractions.
  • Calf pain or swelling (rule out DVT).
  • Dyspnea prior to exertion, dizziness, syncope, or chest pain.

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Common discomforts during pregnancy

• Nausea & Vomiting of Pregnancy (NVP)
  • Etiology: Peak β-hCG and progesterone (8–12 wks).
  • Management: Small frequent meals → Pyridoxine (Vit B6) ± Doxylamine (1st-line) → Promethazine or Ondansetron.
  • Differential: Hyperemesis Gravidarum (>5% pre-pregnancy weight loss, ketonuria, hypokalemic metabolic alkalosis; give thiamine before dextrose to prevent Wernicke encephalopathy).
• Gastroesophageal Reflux Disease (GERD)
  • Etiology: Progesterone-mediated ↓ lower esophageal sphincter (LES) tone + mechanical displacement by gravid uterus.
  • Management: Elevate head of bed, avoid meals <2–3 hr before sleep → Antacids (calcium carbonate) (1st-line) → H2 blockers (famotidine) → PPIs.
  • Differential: Epigastric/RUQ pain in preeclampsia w/ severe features (check BP, LFTs, platelets).
• Constipation & Hemorrhoids
  • Etiology: Progesterone-induced ↓ colonic transit + increased water absorption + oral iron therapy.
  • Management: High-fiber diet, hydration → Bulk-forming laxatives (psyllium), docusate, or PEG (avoid castor/mineral oil); warm sitz baths and topical agents for hemorrhoids.
• Round Ligament Pain
  • Etiology: Stretching of round ligaments during 2nd trimester (frequently right-sided due to uterine dextrorotation).
  • Presentation: Sharp, stabbing, or dull positional groin/lower abdominal pain; normal vitals, soft abdomen, normal fetal heart tones.
  • Management: Reassurance, position modifications, local warmth, acetaminophen.
  • Differential: Appendicitis (appendix displaced superiorly/laterally to RUQ), placental abruption, ovarian torsion.
• Pregnancy-Related Low Back & Pelvic Girdle Pain
  • Etiology: Exaggerated lumbar lordosis + relaxin/progesterone-induced laxity of sacroiliac joints and pubic symphysis.
  • Management: Supportive footwear, maternity pelvic belts, PT, acetaminophen (avoid NSAIDs, especially in 3rd trimester due to premature closure of ductus arteriosus and oligohydramnios). c
• Carpal Tunnel Syndrome (CTS)
  • Etiology: Estrogen/progesterone fluid retention compressing the median nerve beneath flexor retinaculum.
  • Presentation: Bilateral nocturnal paresthesias/numbness in digits 1–3.
  • Management: Neutral-position wrist splints (usually resolves postpartum).
• Dependent (Physiologic) Edema c
  • Etiology: Gravid uterus compresses the IVC and iliac veins → ↑ lower extremity venous hydrostatic pressure.
  • Presentation: Bilateral, gradual ankle/foot pitting edema without proteinuria or hypertension.
  • Management: Leg elevation, left lateral decubitus (LLD) positioning, compression stockings (diuretics are contraindicated).
  • Differential: Preeclampsia (sudden non-dependent/facial edema + HTN + proteinuria), DVT (unilateral calf swelling/erythema → obtain compression duplex US).
• Supine Hypotensive Syndrome
  • Etiology: IVC compression when supine (>20 wks) → ↓ venous return (preload) → ↓ cardiac output → hypotension and syncope.
  • Management: Immediate left lateral decubitus (LLD) position.
• Urinary Frequency & Nocturia
  • Etiology: Increased GFR (~50%) + mechanical compression of the bladder.
  • Differential: UTI / Asymptomatic Bacteriuria (ASB) (presence of dysuria/fever or positive urine culture; ASB must always be treated in pregnancy to prevent pyelonephritis and preterm labor).
• Physiologic Leukorrhea
  • Etiology: Estrogen-induced stimulation of cervical glands and epithelial shedding.
  • Presentation: Thin, white/clear, non-pruritic, non-malodorous vaginal discharge (pH ≤4.5).
  • Differential: PROM (fluid pooling, (+) nitrazine blue, (+) ferning), Candidiasis (pseudohyphae, pruritus), Bacterial Vaginosis (clue cells, fishy odor, pH >4.5), Trichomoniasis (motile flagellates, strawberry cervix).

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Initial Visit (First Trimester, ~8–10 Weeks)

• Baseline Labs (All Patients):
  • Blood Type & Rh Status: Rh(D) typing + indirect Coombs antibody screen.
  • CBC: Screen for anemia and baseline platelets.
  • Infectious Screening:
    • HIV: Opt-out universal screening.
    • Syphilis: RPR/VDRL or treponemal EIA.
    • Hepatitis B: HBsAg.
    • Rubella & Varicella: IgG titers (document immunity; live vaccines contraindicated during pregnancy).
    • Chlamydia & Gonorrhea: NAAT/PCR (screen if age <25 or high risk).
  • Urinalysis & Urine Culture: Universal screening for asymptomatic bacteriuria (treat if ≥10⁵ CFU/mL to prevent pyelonephritis and preterm labor).
  • Cervical Cytology: Pap test only if due based on routine screening guidelines.
• Genetic / Aneuploidy Screening Options:
  • Cell-free fetal DNA (cfDNA): Performed at ≥10 weeks. Highest sensitivity/specificity for Trisomies 21, 18, and 13.
  • First-Trimester Combined Test (10–13 weeks): Nuchal translucency (NT) on US + pregnancy-associated plasma protein A (PAPP-A) + β-hCG.
  • Chorionic Villus Sampling (CVS): Performed at 10–13 weeks. Diagnostic/confirmatory (karyotype/microarray); carries ~0.2–0.5% risk of fetal loss.

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Second Trimester (Weeks 13–27)

• Aneuploidy & Neural Tube Defect (NTD) Screening (15–20 Weeks):
  • Maternal Serum Alpha-Fetoprotein (MSAFP) or Quad Screen (MSAFP, β-hCG, unconjugated estriol, inhibin A):
    • ↑ MSAFP: Neural tube defects (anencephaly, spina bifida), abdominal wall defects (gastroschisis, omphalocele), multiple gestation, underestimated gestational age (most common).
    • Trisomy 21 (Down syndrome): ↑ hCG, ↑ Inhibin A, ↓ MSAFP, ↓ Estriol (“HIgh” = HCG & Inhibin).
    • Trisomy 18 (Edwards syndrome): ↓ All four markers (inhibin A may be normal).
  • Next Step for Abnormal MSAFP/Quad: Ultrasound (evaluate gestational age, viability, anatomy, and multiples).
  • Amniocentesis: Performed at ≥15 weeks. Diagnostic/confirmatory for abnormal screening results.
• Anatomy Ultrasound (18–22 Weeks):
  • Assess fetal anatomical survey, placental location (rule out placenta previa), amniotic fluid index, and cervical length.

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Third Trimester (Weeks 28–Delivery)

• 24–28 Weeks:
  • Gestational Diabetes Mellitus (GDM) Screening:
    • 1-hour 50-g oral glucose challenge test (GCT). If glucose ≥140 mg/dL (or ≥130 mg/dL) → diagnostic 3-hour 100-g oral glucose tolerance test (OGTT).
  • Repeat CBC: Assess for physiologic vs. iron-deficiency anemia (Hb <10.5 g/dL in 2nd/3rd trimester is abnormal).
  • Repeat Antibody Screen: For all Rh(D)-negative mothers.
• 28 Weeks:
  • Anti-D Immune Globulin (RhoGAM): Administer 300 µg at 28 weeks to all unsensitized Rh(D)-negative mothers.
  • Postpartum: Give second dose within 72 hours of delivery if the infant is Rh(D)-positive. Perform Kleihauer-Betke test or rosette test to determine if a higher dose is needed after fetomaternal hemorrhage.
• 36 0/7 to 37 6/7 Weeks:
  • Group B Streptococcus (GBS) Screening: Rectovaginal swab culture.
    • No swab needed if: Pt had GBS bacteriuria in current pregnancy OR prior infant with invasive GBS disease (automatically receive intrapartum prophylaxis).
    • Intrapartum Prophylaxis: IV Penicillin G (or Ampicillin) initiated at rupture of membranes or onset of labor.
    • Penicillin Allergy: Cefazolin (low-risk anaphylaxis), Clindamycin (if isolate is sensitive to both clindamycin and erythromycin), or Vancomycin (if resistant or high-risk severe allergy).
  • Repeat STI Screening: HIV, RPR, and NAAT for Gonorrhea/Chlamydia in high-risk patients.

Vaccines in Pregnancy

• Recommended / Indicated:
  • Tdap: Administer between 27 and 36 weeks of gestation during every pregnancy (optimizes neonatal passive pertussis immunity).
    • Placental active IgG transport increase exponentially in the 3rd trimester
  • Inactivated Influenza: Administer in any trimester during flu season. c
  • COVID-19: Administer in any trimester.
  • RSV Vaccine (Abrysvo): Administer between 32 0/7 and 36 6/7 weeks if delivery is expected during RSV season.
• Contraindicated (Live Attenuated Vaccines):
  • MMR, Varicella, and Live Attenuated Influenza (nasal spray).
  • Avoid pregnancy for at least 1 month after receiving MMR or Varicella vaccine.

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Prophylaxis & Supplementation

• Folic Acid:
  • Average risk: 0.4 mg (400 µg)/day, start ≥1 month preconception.
  • High risk (prior child with NTD, taking antiepileptic drugs like valproate/carbamazepine): 4.0 mg/day.
• Low-Dose Aspirin (81 mg/day):
  • Initiate at 12–16 weeks until delivery for Preeclampsia Prophylaxis in high-risk patients:
    • High-risk factors: Prior preeclampsia, chronic HTN, pregestational DM, renal disease, autoimmune disease (SLE, APS), multifetal gestation.