Clinical overview
"High-risk pregnancy" is not a diagnosis — it is a working judgement that a particular woman, by virtue of her age, parity, past obstetric performance or a coexisting condition, carries a materially higher probability of an adverse maternal or perinatal outcome than the unselected obstetric population. The whole point of risk stratification is action: it changes where she should book and deliver (the appropriate level of care), how often she is seen, what is screened for, and what is anticipated at delivery. For the FCOG(SA) candidate, this objective is squarely a higher-order-thinking-skills (HOTS) topic — you are not asked to list dangers but to reason about why a given demographic carries a given risk, how large that risk is in rough terms, and what you would do differently in a South African district, regional or tertiary setting.
The recurring South African theme is that the demographics that drive risk here are not identical to those in high-income guidelines. We have a high burden of adolescent pregnancy, a large number of grand multiparous women in rural districts, a maternal HIV seroprevalence that reshapes almost every risk category, and a referral system stratified by level of care where the central skill is recognising the woman who must not deliver at the clinic. The leading direct and indirect causes of maternal death in the Saving Mothers reports — obstetric haemorrhage, hypertensive disease, and non-pregnancy-related infection (chiefly HIV) — concentrate disproportionately in exactly these higher-risk groups. Effective risk assessment at booking is therefore the single highest-yield preventive intervention in obstetrics.
Core knowledge
Advanced maternal age (AMA)
Advanced maternal age is conventionally defined as 35 years or older at the expected date of delivery, with a further "very advanced" stratum sometimes set at ≥40 or ≥45. The risks rise on a continuum rather than at a threshold, and they are partly biological (ageing oocytes, ageing vasculature) and partly because comorbidity accumulates with age.
The mechanisms worth holding in your head:
- Aneuploidy rises steeply because of increased meiotic non-disjunction in ageing oocytes. The risk of trisomy 21 at term is classically quoted around 1 in 1,500 at age 20, ~1 in 350 at age 35, and ~1 in 100 by age 40 (standard teaching — treat as orders of magnitude, not exact). This is the historical basis for offering aneuploidy screening and counselling and for the age-35 cut-off itself.
- Hypertensive disease and pre-eclampsia are more common, partly through stiffer maternal vasculature and a higher baseline prevalence of chronic hypertension.
- Gestational and pre-existing diabetes increase with age and with the rising BMI that often accompanies it.
- Placental dysfunction — both placental insufficiency causing fetal growth restriction and, at the other extreme, abruption and praevia — is commoner.
- Stillbirth risk rises modestly but consistently with maternal age, independent of comorbidity, which is one reason some services consider timed delivery around term in older women.
- Operative delivery (caesarean and instrumental) rates are higher, reflecting both medical indications and reduced myometrial efficiency.
Teenage / adolescent pregnancy
Adolescent pregnancy (broadly <18, with the highest risk <16 or within ~2 years of menarche) is a major South African public-health issue. The risks are a blend of biological immaturity and powerful social determinants.
- Pre-eclampsia and eclampsia are over-represented in primigravid adolescents — nulliparity itself is a pre-eclampsia risk factor and adolescents are usually nulliparous.
- Preterm birth and low birth weight are commoner.
- Cephalopelvic disproportion and obstructed labour are a real concern in the very young whose pelvis has not completed growth, with the historic downstream risk of obstetric fistula where labour is neglected.
- Anaemia and undernutrition are frequent and compound haemorrhage risk.
- Mental health — depression, anxiety and the consequences of coercion or gender-based violence — must be actively screened for; adolescent pregnancy is frequently non-consensual or exploitative, which has child-protection and legal implications.
- Late booking, poor attendance, and disengagement are the rule rather than the exception, so a single contact must achieve a great deal.
Grand multiparity
Grand multiparity is classically para 5 or more (≥5 previous births beyond viability); "great-grand multiparity" is sometimes set at ≥10. It remains common in parts of rural South Africa.