Antenatal Care

• Birth rate ~35,000–40,000 per year in HK (declining trend)
• Maternal mortality < 5/100,000 (comparable to developed nations)
• Caesarean section rate ~25–30% in public hospitals
• GDM prevalence ~15–20% (high due to ethnic predisposition)
• HBsAg carriage rate ~5–8% in HK Chinese women

1. Folic acid supplementation: 0.4 mg/day (routine) → prevents neural tube defects ^[6][7]
   • High-risk women (previous NTD, on anti-epileptics, diabetes): 5 mg/day
2. Medication review:
   • Warfarin: teratogenic (highest risk 6–12 weeks) ^[4] → switch to LMWH before conception
   • ACE-i/ARBs: contraindicated → switch to labetalol/nifedipine/methyldopa
   • Sodium valproate: major teratogen (NTD) → switch if possible ^[8]
   • Statins, retinoids, methotrexate: stop pre-conception
   • ATD: PTU preferred in 1st trimester, then switch to carbimazole ^[9]
3. Vaccination:
   • Rubella: check immunity; vaccinate if non-immune (live vaccine → avoid conception for 4 weeks after)
   • Varicella: if non-immune
   • HPV: complete series before pregnancy
4. Chronic disease optimisation:
   • DM: target HbA1c < 6.5% before conception; switch to insulin if on OHAs
   • Hypertension: switch to pregnancy-safe agents
   • Epilepsy: simplify regimen, avoid valproate
   • Hepatitis B: assess viral load; TDF if HBV DNA > 200,000 IU/mL (start 28–32 weeks) ^[2][10]
5. Lifestyle counselling: ^[7]
   • Smoking, alcohol, substance abuse: stop for BOTH parents
   • No known safe level of alcohol
   • Optimal diet, weight — both too heavy and too light associated with adverse fetal outcomes
   • Intimate partner violence screening — women may not proactively volunteer → use structured checklists

• Timing: ~10–14 weeks ^[11]
  • Not earlier because a lot of early pregnancies are lost
  • Not later to facilitate 1st trimester Down syndrome screening (before 13+6) and accurate dating (CRL up to 13+6) ^[11]

Symptoms of pregnancy: ^[11]

• Secondary amenorrhoea
• Nausea/vomiting (commonly ≤6w–3m, due to hCG; ± hyperemesis gravidarum if severe)
• Increased urinary frequency (pressure of gravid uterus on bladder, diminishes ≤12w)
• Excessive lassitude/lethargy (disappears after 12w)
• Breast tenderness and heaviness (↑progesterone)
• Fetal movements: usually not noticed until 20w (primipara) or 18w (multipara) ^[11]

Urinary/serum hCG: detectable 6 days after ovulation, usually test +ve from 4 weeks ^[11]

Ultrasound landmarks: ^[11]

• Fetal sac: visible 4.5–5 weeks
• Yolk sac: 5–6 weeks to 10 weeks
• Fetal pole with cardiac activity: 5.5–6 weeks

Gestational age: defined as time from 1st day of LMP ^[11]

EDD = LMP + 280 days or LMP + 9 months + 7 days (Naegele's rule) ^[11]

• If cycle > 28 days, add (cycle length − 28 days)

Ultrasound measurements: ^[11]

• CRL (crown–rump length): before 13w+6d
• Head circumference (HC): 14–20 weeks

• Demographics: age, race
• HPC: symptoms of pregnancy, dating (LMP), prior AN care
• Past Obstetric History: all previous pregnancies including miscarriages and terminations
  • Antenatal complications (pre-eclampsia, APH)
  • Labour and delivery: gestational age, duration, mode, complications (prolonged labour, malpresentation)
  • Puerperal: complications (PPD, PPH)
  • Neonatal: birth weight, sex, current health, complications
• Past Gynaecological History: problems, procedures, menstrual regularity, last Pap smear
• PMH/PSH/Psychiatric history
• Family history
• Social history: smoking, drinking, substance abuse ^[7]

First antenatal visit:

• General: inspection, maternal height/weight/BMI, BP, urinalysis (protein/glucose) ^[3]
  • Low BMI (< 20) → higher risk of IUGR ^[11]
  • High BMI (> 30) → much higher risk of GDM, pre-eclampsia, need for C/S, anaesthetic difficulties ^[11]
• Lymph nodes and thyroid ^[3]
• Oedema: feet, lower legs, sacral ^[3]
• CVS: auscultation (flow murmur in 80% at end of 1st trimester is physiological) ^[3]
• Respiratory: auscultation ^[3]
• Breast: palpation — note CA breast during pregnancy a/w ↑rate of progression ^[12]
• Abdominal exam: scars (esp. previous C/S) ^[12]
• ± Pelvic exam:
  • Speculum: not indicated unless PV bleeding or discharge ^[12]
  • Bimanual: for estimation of uterus size ^[12]

• Q4w from 0–28 weeks
• Q2–3w from 28–36 weeks
• Q1w from 36 weeks onwards

Now: tailored to attendance for screening tests, increased frequency if risk factors present ^[12]

Screening for fetal anomalies and Down syndrome: ^[1]

• Screening programme for specific abnormalities — screening for fetal Down syndrome, thalassaemia ^[1]
• The combined first-trimester screen has detection rate ~85–90% with 5% false positive rate
• Non-invasive prenatal testing (NIPT/cfDNA): available in HK, high sensitivity/specificity for T21 (> 99%), used as secondary screen or primary screen (patient-funded in public sector)

• MCV < 80 fL at booking → check iron status (ferritin/Fe profile)
• If iron replete and MCV still low → suspect thal trait → Hb electrophoresis/HPLC
• Test partner's MCV ^[12]
  • If both parents are carriers of the same type → genetic counselling → offer prenatal diagnosis (CVS/amniocentesis)
  • α-thal: if both parents are α⁰ carriers (SEA deletion) → risk of Bart's hydrops fetalis (lethal)
  • β-thal: risk of β-thal major → lifelong transfusion dependence

• All women: ABO/Rh typing at booking ^[12]
• Rh-negative women (~5% of Chinese women):
  • Anti-D prophylaxis at 28 weeks (routine)
  • Anti-D within 72 hours after any sensitising event (miscarriage, APH, amniocentesis, ECV, delivery of Rh+ baby)
  • Indirect Coombs test (antibody screen) at booking and 28 weeks
• If antibodies detected → serial titres → if rising → referral for MCA Doppler (peak systolic velocity) to assess for fetal anaemia

GBS detail: ^[10]

• Reservoir: GI tract (primary, 20–40% adults), vaginal colonisation (10–30% pregnant women)
• Neonatal infection: ~1/1000 births in HK
• Risk of early-onset infection 1–2% in colonised mothers
• Swab procedure: 2 separate locations without speculum — low vaginal swab at introitus + rectal swab through anal sphincter

• Screening: OGTT at 24–28 weeks ^[1]
• 75g OGTT — WHO/IADPSG criteria:
  • Fasting ≥ 5.1 mmol/L
  • 1-hour ≥ 10.0 mmol/L
  • 2-hour ≥ 8.5 mmol/L
  • Any ONE value abnormal = GDM
• Risk factors for GDM: obesity, age > 35, FHx DM, previous GDM, previous macrosomia, PCOS, ethnicity (Chinese)
• Management: dietary counselling → SMBG → if targets not met → insulin (metformin used increasingly)
• Monitoring: serial growth US (macrosomia, polyhydramnios); fetal surveillance from 36w; plan delivery by 40w

• BP at every visit; urinalysis for protein at every visit ^[3]
• First-trimester risk assessment: maternal factors + uterine artery Doppler + PlGF + MAP + PAPP-A
• High-risk women → low-dose aspirin 150 mg nocte from 12 weeks to 36 weeks

• Diet: 2000–2500 kcal/day in last 2 trimesters
  • Balanced CHO, protein (60–80 g/day), fats
  • Vitamins: folate (0.4 mg/day), iodine, vitamin D (note RFs)
• Exercise: reasonable activity, no need to limit beyond excessive exertion and fatigue ^[14]
• Coitus: no C/I unless: ^[14]
  • Risk of miscarriage (threatened miscarriage, recurrent miscarriage Hx)
  • Evidence of PROM, placenta praevia, Hx of APH
• Breast care: good personal hygiene, adequate mechanical support, counselling
  • Colostrum: may leak from nipple especially in 3rd trimester and in multiparous women ^[14]
• Use of drugs: ^[14]
  • Analgesics: paracetamol safe; NSAID C/I after 35 weeks (risk of premature ductus arteriosus closure)
  • Vomiting: metoclopramide safe

Cardiac disease in pregnancy: ^[15]

• Combined obstetric/cardiac clinic
• Echocardiogram at booking + 28 weeks
• Monitor for HF symptoms: SOBOE, orthopnoea, PND
• Warfarin must be stopped in 1st trimester + 2 weeks before EDC ^[4]
• LMWH: insufficient for mechanical prosthetic valves but safe as does not cross placenta ^[4]
• Epidural preferred intrapartum (↓stress on heart)
• Syntocinon instead of syntometrine (syntometrine causes intense vasoconstriction → ↑↑afterload) ^[15]

Thrombophilia in pregnancy: ^[4]

• Low-dose aspirin 100 mg nocte + LMWH for antiphospholipid syndrome
• Minimise immobility: do NOT injudiciously prescribe bed rest
• Adequate hydration, ± compression stockings

HIV-positive mother: ^[10]

• Avoid fetal scalp blood sampling, scalp electrode insertion, rupture of membranes
• C-section offered unless prolonged ROM / advanced labour / adequate cART (VL < 50)
• Avoid breastfeeding (unless no alternative; if on cART risk is much lower)
• Post-exposure prophylaxis for baby: zidovudine 300 mg PO BD × 7 days + lamivudine 150 mg PO BD × 7 days ^[10]

• ↑ risk of chromosomal abnormalities → emphasis on first-trimester combined screening / NIPT
• ↑ risk of GDM, pre-eclampsia, C-section
• May require more frequent monitoring

• Determine chorionicity at first scan (critical for management)
• More frequent growth scans (Q2w for MCDA; Q4w for DCDA)
• Screen for twin-twin transfusion syndrome (MCDA)
• Higher risk of preterm labour, pre-eclampsia, GDM

1. "Outline the schedule and content of routine antenatal care" — use the timeline table
2. "A 32-year-old woman presents at 10 weeks. What investigations would you arrange?" — list all booking investigations with rationale
3. "Discuss screening for Down syndrome in pregnancy" — cover combined first-trimester screen, NIPT, diagnostic tests
4. "A woman is Rh-negative. How would you manage her pregnancy?" — anti-D timing, antibody screening, sensitising events
5. OSCE station: Booking visit history taking — demonstrate systematic approach

"Antenatal care is a longitudinal screening and prevention programme with the goal of a healthy mother and healthy baby. I would structure my approach chronologically: pre-pregnancy counselling, booking visit at 10–14 weeks, first-trimester screening, anomaly scan at 18–22 weeks, GDM screening at 24–28 weeks, GBS screening at 35–37 weeks, and weekly visits from 36 weeks. At every visit, I check BP, urinalysis, SFH, fetal heart, and maternal wellbeing."