Key Facts

Antenatal care is a cornerstone of obstetric practice, aimed at ensuring optimal outcomes for mother and baby. The UK model provides structured care through a schedule of appointments with midwives and obstetricians, incorporating screening, health promotion, and early detection of complications.

Epidemiology

Approximately 640,000 births occur annually in England and Wales. The UK maternal mortality rate is approximately 9 per 100,000 maternities (MBRRACE-UK). Perinatal mortality (stillbirth + early neonatal death) is approximately 6 per 1,000 births. The majority of maternal deaths are considered to have modifiable factors.

Aetiology

Antenatal care addresses a wide range of potential complications:

• Pre-existing medical conditions: Diabetes, hypertension, epilepsy, autoimmune disease, cardiac disease
• Pregnancy-specific conditions: Pre-eclampsia, gestational diabetes, placenta praevia, preterm labour
• Fetal conditions: Growth restriction, structural anomalies, chromosomal abnormalities
• Infectious: Group B streptococcus, HIV, hepatitis B, syphilis, rubella, CMV, toxoplasmosis

Pathophysiology

Pregnancy involves profound physiological adaptations:

• Cardiovascular: 40-50% increase in blood volume; cardiac output increases 30-50%; peripheral vascular resistance decreases
• Haematological: Dilutional anaemia; hypercoagulable state (5× increased VTE risk)
• Renal: GFR increases 40-50%; ureteric dilatation
• Respiratory: Increased minute ventilation; mild respiratory alkalosis; reduced FRC
• Endocrine: hCG (first trimester), HPL and oestrogen/progesterone rise throughout

Routine Antenatal Schedule (NICE NG201)

• Booking (by 10 weeks): Full history, risk assessment, screening bloods, BMI, BP, urine
• 11-14 weeks: Dating/combined screening scan
• 16 weeks: Blood results review, screening results discussion
• 18-20+6 weeks: Anomaly scan
• 25 weeks (nulliparous): Measure fundal height, BP, urine
• 28 weeks: FBC, blood group antibodies, anti-D if Rh-negative, OGTT if indicated, BP, urine
• 31 weeks (nulliparous): Review results, BP, urine, fundal height
• 34 weeks: Review, second anti-D if indicated, information about labour
• 36 weeks: Check fetal presentation, discuss birth plan, BP, urine
• 38 weeks: BP, urine, discuss options if not delivered by term
• 40 weeks (nulliparous): Discuss post-dates management, offer membrane sweep
• 41 weeks: Offer membrane sweep, discuss induction of labour

Common Symptoms by Trimester

• First: Nausea/vomiting, fatigue, breast tenderness, urinary frequency
• Second: Quickening (fetal movements from ~18-20 weeks), round ligament pain, heartburn
• Third: Braxton Hicks contractions, back pain, oedema, breathlessness, pelvic pressure

Red Flags

• Vaginal bleeding — threatened miscarriage, ectopic, placenta praevia, abruption
• Severe headache, visual disturbance, epigastric pain, sudden oedema — pre-eclampsia
• Reduced fetal movements — arrange urgent assessment (RCOG guidance)
• Fever with abdominal pain — consider chorioamnionitis, UTI, appendicitis
• Preterm contractions (<37 weeks) — risk of preterm delivery
• Persistent vomiting with weight loss and ketonuria — hyperemesis gravidarum

Bedside

• Blood pressure: At every visit; ≥140/90 = gestational hypertension if after 20 weeks
• Urinalysis: Proteinuria (pre-eclampsia), glycosuria (gestational diabetes screening), nitrites/leucocytes (UTI)
• Fundal height: From 24 weeks; plot on customised growth chart (GAP/GROW); discrepancy of >2cm → USS
• Fetal heart auscultation: Doppler from ~12 weeks; pinard from ~28 weeks
• BMI: At booking — risk assessment for GDM, VTE, pre-eclampsia

Bloods

• Booking bloods: FBC, blood group + antibodies, rubella IgG (historical — no longer routinely tested), syphilis, hepatitis B surface antigen, HIV
• 28-week bloods: FBC, blood group antibodies
• OGTT (24-28 weeks): If risk factors for GDM (BMI ≥30, previous GDM, family history DM, South Asian/Black ethnicity) — fasting ≥5.6 or 2h ≥7.8 = GDM (NICE NG3)
• PlGF-based testing: If pre-eclampsia suspected between 20-36 weeks (NICE DG49)

Imaging

• Dating USS (11-14 weeks): Crown-rump length, nuchal translucency (combined screening), viability, multiple pregnancy
• Anomaly USS (18-20+6 weeks): Structural survey — 11 conditions screened for (cardiac, neural tube, renal, abdominal wall, skeletal)
• Growth scans: USS for estimated fetal weight (EFW) if SGA suspected or high-risk pregnancy
• Presentation USS at 36 weeks: If clinical uncertainty about presentation

Special Tests

• Combined screening test (11-14 weeks): NT + β-hCG + PAPP-A — risk for T21, T18, T13
• NIPT (Non-invasive prenatal testing): Cell-free fetal DNA from maternal blood; >99% sensitivity for T21; offered as contingent screening
• Amniocentesis/CVS: Diagnostic — karyotype/microarray; amnio from 15 weeks, CVS from 11 weeks; ~1% miscarriage risk
• Group B streptococcus: Not routinely screened in the UK; treat if incidentally found or if previous GBS-affected baby

Non-pharmacological

• Folic acid 400mcg OD: From preconception to 12 weeks (5mg if high-risk — epilepsy, diabetes, previous NTD)
• Vitamin D 10mcg (400 IU) OD: Throughout pregnancy and breastfeeding
• Dietary advice: Avoid raw/undercooked meat, unpasteurised dairy, liver, certain fish (high mercury), alcohol
• Exercise: Moderate exercise encouraged (30 min/day)
• Smoking cessation: Offer referral to stop smoking services at every appointment
• Mental health screening: At booking and postnatally — use Whooley questions/PHQ-9
• Birth planning: Discuss preferences, birth setting options (home, MLU, hospital)

Pharmacological

• Aspirin 150mg nocte from 12 weeks: If ≥1 high-risk factor (previous pre-eclampsia, CKD, autoimmune disease, diabetes, chronic hypertension) or ≥2 moderate-risk factors (nulliparity, age >40, BMI >35, FH pre-eclampsia, multiple pregnancy, IVF)
• Anti-D immunoglobulin: For Rh-negative women — routine at 28 weeks (1500 IU); within 72 hours of sensitising events (bleeding, amniocentesis, external cephalic version)
• Iron supplementation: If Hb <110 g/L first trimester, <105 g/L second/third trimester — ferrous sulfate 200mg BD-TDS
• VTE prophylaxis: LMWH (e.g., enoxaparin 40mg OD SC) if risk factors (RCOG guidelines)

Surgical/Interventional

• External cephalic version (ECV): Offered from 36 weeks for breech presentation (NICE NG201)
• Membrane sweep: Offered from 40 weeks (nulliparous) or 41 weeks (parous)
• Induction of labour: Offered from 41+0 weeks if not delivered (NICE NG207)
• Caesarean section: Planned for specific indications (placenta praevia, malpresentation, previous classical section, etc.)

Referral Criteria

• High-risk pregnancy (pre-existing medical conditions, previous complications) — consultant-led care
• Low-risk — midwife-led care with obstetric review only if complications arise
• Mental health concerns — perinatal mental health team
• Fetal anomaly detected — fetal medicine specialist

• UK maternal mortality: ~9 per 100,000 maternities; leading causes: cardiac disease, thromboembolism, sepsis, pre-eclampsia
• Perinatal mortality: ~6 per 1,000 births; leading causes: prematurity, congenital anomalies, unexplained stillbirth
• Pre-eclampsia: Affects ~2-5% of pregnancies; aspirin prophylaxis reduces risk by ~18% (ASPRE trial)
• GDM: Affects ~5-7% of pregnancies; managed with diet ± metformin ± insulin; resolves postpartum but ~50% develop T2DM within 10-20 years
• Preterm birth: ~7-8% of UK births; single biggest cause of neonatal mortality
• Antenatal care quality: MBRRACE-UK data shows modifiable factors in the majority of maternal deaths

Antenatal Screening Timeline Summary

Pre-Eclampsia Risk Factors (NICE NG133)