What is the standard guideline for antenatal care in a pregnant woman from early pregnancy until delivery?

Standard Antenatal Care Guideline from Early Pregnancy to Delivery

All pregnant women should undergo comprehensive risk assessment at their first antenatal visit (ideally before 12 weeks), followed by risk-stratified monitoring schedules after 20 weeks, with specific attention to pre-eclampsia screening, preventive interventions, and timely specialist referral for high-risk conditions.

Early Pregnancy Assessment (First Trimester)

Initial Risk Stratification

Every pregnant woman requires systematic assessment for pre-eclampsia risk factors at the first antenatal contact to determine the appropriate care pathway. 1, 2

Identify the following risk factors at booking: 3

• First pregnancy (nulliparity) - RR 2.91 1, 2
• Previous pre-eclampsia - RR 7.19 1, 2
• Age ≥40 years - RR 1.68-1.96 1, 2
• Body mass index ≥35 3
• Family history of pre-eclampsia (mother or sister) - RR 2.90 2
• Booking diastolic blood pressure ≥80 mm Hg 3
• Proteinuria at booking (≥+ on more than one occasion or ≥300 mg/24h) 3
• Pregnancy interval ≥10 years since last baby 3
• Multiple pregnancy - RR 2.93 1, 2
• Pre-existing hypertension (diastolic BP ≥90 mm Hg) 3
• Pre-existing renal disease 3
• Pre-existing diabetes - RR 3.56 1, 2
• Antiphospholipid antibodies - RR 9.72 (highest risk) 1, 2

Mandatory Specialist Referral Before 20 Weeks

Refer women for specialist input before 20 weeks if they have any ONE of the following: 3, 1

• Previous pre-eclampsia
• Multiple pregnancy
• Pre-existing hypertension or booking diastolic BP ≥90 mm Hg
• Pre-existing renal disease or booking proteinuria
• Pre-existing diabetes
• Presence of antiphospholipid antibodies
• Any TWO other risk factors from the list above 3

Preventive Interventions to Initiate in First Trimester

Low-dose aspirin (100-150 mg daily) should be started before 16 weeks (but definitely before 20 weeks) in women with: 1, 2, 4

• Major risk factors: prior pre-eclampsia, chronic hypertension, pregestational diabetes, antiphospholipid antibodies
• Two or more minor risk factors
• Continue until 37 weeks gestation 1

Calcium supplementation (1200 mg daily) should be initiated at first antenatal contact in women with: 1, 4

• Low dietary calcium intake (<600 mg/day)
• Can be taken with iron-folic acid supplements despite minor interaction concerns 1

Monitoring Schedule After 20 Weeks

Risk-Stratified Monitoring Frequency

The monitoring schedule is determined by the number of risk factors identified at booking. 3, 1

Level 1 (Low Risk) - Women with NO risk factors: 3

• Follow local protocols and NICE guidelines for low-risk multiparous women
• Typical schedule: weeks 16,28,34,36,38,40, and 41 3

Level 2 (Moderate Risk) - Women with ONE risk factor (and no criteria requiring early specialist referral): 3, 1

• 24-32 weeks gestation: Maximum 3-week intervals between assessments 3, 1
• 32 weeks to delivery: Maximum 2-week intervals between assessments 3, 1

The rationale for this schedule is that pre-eclampsia before 32 weeks has the most serious outcomes, with an average interval of 14 days between diagnosis and delivery, and many women requiring delivery within 72 hours. 3

Content of Each Assessment After 20 Weeks

At every assessment after 20 weeks, screen for the following signs and symptoms of pre-eclampsia: 3

• New hypertension (≥140/90 mm Hg)
• New proteinuria (≥+ on dipstick, protein:creatinine ratio ≥30 mg/mmol, or ≥300 mg/24h)
• Symptoms of headache or visual disturbance
• Epigastric pain or vomiting
• Reduced fetal movements
• Small for gestational age infant

Action Thresholds for Step-Up Care

New hypertension without proteinuria: 3

• Diastolic BP 90-99 mm Hg: Refer for hospital assessment within 48 hours
• Diastolic BP 90-99 mm Hg WITH any symptom: Refer for same-day hospital assessment
• Diastolic BP ≥100 mm Hg: Immediate referral regardless of symptoms

Pre-eclampsia is defined as new hypertension (≥140/90 mm Hg) after 20 weeks with proteinuria (>0.3g/24h or albumin:creatinine ratio ≥30 mg/mmol), maternal organ dysfunction, or uteroplacental dysfunction. 1, 4

Special Populations

Women with Liver Disease or Liver Transplant

Pregnant liver transplant recipients require increased frequency of review with monitoring for: 3

• Gestational hypertension and pre-eclampsia
• Gestational diabetes
• Acute kidney injury
• Low-dose aspirin should be initiated in the first trimester for pre-eclampsia prophylaxis 3
• Increased surveillance for preterm birth and fetal growth restriction 3

Women with Cirrhosis or Portal Hypertension

Screening endoscopy should be performed within 1 year prior to conception to assess for varices. 3 Beta-blockers should be continued during pregnancy for variceal prophylaxis unless contraindicated. 3

Critical Pitfalls to Avoid

Blood pressure measurement technique is critical - errors have been implicated in maternal deaths. 3 Ensure proper technique with appropriate cuff size and positioning.

Women with no risk factors can still develop pre-eclampsia. 3 All women should be educated about symptoms and have 24-hour access to healthcare professionals, as pre-eclampsia can progress to life-threatening complications within 2 weeks of diagnosis. 3

The 20-week threshold is pathophysiologically significant - it reflects completion of placental development and spiral artery remodeling. 4 Hypertension before 20 weeks represents pre-existing or chronic hypertension, not gestational hypertension or pre-eclampsia. 4

Absence of antenatal care is strongly associated with eclampsia and fetal death. 3 Regular monitoring is essential even in apparently low-risk pregnancies.