Clinical overview
Nutrition, exercise, supplementation and gestational weight gain are the substrate on which a healthy pregnancy is built, and they are among the few modifiable determinants of fetal and maternal outcome that you can influence from the very first antenatal contact. The registrar who treats these as "lifestyle advice" — a box to tick — misses the point. Periconceptional folate prevents neural tube defects; iron and the management of anaemia reduce the depth from which a woman bleeds at delivery; calcium supplementation lowers pre-eclampsia risk in deficient populations; appropriate weight gain sits between the twin harms of growth restriction at one extreme and macrosomia, gestational diabetes and operative delivery at the other. In a South African public-sector clinic these decisions are made against a backdrop of food insecurity, a generalised HIV epidemic, high rates of obesity coexisting with micronutrient deficiency ("the double burden"), and a maternal mortality profile in which haemorrhage, hypertension and HIV-associated infection dominate.
Your job during a "discuss" objective like this is to integrate the evidence into concrete, defensible counselling: what every pregnant woman should take, what she should eat and avoid, how much and what kind of exercise is safe, how much weight she should gain across her BMI categories, and which of these recommendations diverge between international guidance and the SA National Integrated Maternal and Perinatal Care Guideline (NDoH, 2024). This chapter assumes the booking framework of Antenatal booking and the SA service architecture in SA maternity guidelines, and it feeds directly into the high-risk stratification of High-risk pregnancy factors and the medical-disease overlap of Medical complications in pregnancy.
Core knowledge
Physiological demand and the energy economy of pregnancy
Pregnancy is not a state of "eating for two". Total additional energy cost across a singleton pregnancy is modest and back-loaded: standard teaching is that there is essentially no extra requirement in the first trimester, a small increment in the second, and the largest (still only a few hundred kilocalories per day) in the third — flag this as textbook physiology rather than a guideline threshold. Blood volume expands by roughly 40–50%, plasma proportionally more than red-cell mass, producing the physiological dilutional fall in haemoglobin that you must not mistake for pathological anaemia. The fetus is a relatively efficient parasite of maternal stores for energy but an obligate consumer of specific micronutrients — folate, iron, iodine, calcium and vitamin D — whose maternal stores are easily exhausted, which is why targeted supplementation matters more than gross calorie counting.
The key micronutrients
Folate / folic acid. The single most important periconceptional supplement. Adequate folate around conception and through early organogenesis prevents neural tube defects (NTDs) — anencephaly and spina bifida — which close by around the end of the fourth week after conception, i.e. before many women know they are pregnant. The standard recommendation is to start folic acid before conception and continue through the first trimester. The SA NDoH Maternity Guideline (NDoH, 2024) and international antenatal guidance (NICE NG201) both recommend routine periconceptional folic acid; a higher dose is advised for women at high risk of NTD — previous affected pregnancy, diabetes, on anti-epileptic drugs, obesity, or on certain HIV regimens. The commonly taught figures are 0.4 mg daily routine and 5 mg daily for high-risk women; treat the exact milligram values as standard teaching and confirm against the current NDoH/EML before prescribing.
Iron. Iron-deficiency anaemia is endemic in SA pregnancy and is both a direct contributor to maternal morbidity and a reducer of the reserve a woman brings to a postpartum haemorrhage — anaemia is repeatedly highlighted as an aggravating factor in the Saving Mothers (NCCEMD) reports. Routine antenatal iron (with folate) supplementation is SA policy. The diagnostic threshold and treatment intensity depend on the haemoglobin level and trimester; the WHO/SA convention treats Hb below roughly 11 g/dL in the first and third trimesters as anaemia (slightly lower mid-pregnancy because of dilution) — cite these as conventional cut-offs and verify the exact trimester-specific values in the current guideline. Severe or symptomatic anaemia, or failure to respond to oral iron, warrants investigation (iron studies, exclude other causes including HIV, parasitic infection and haemoglobinopathy) and may require parenteral iron or, rarely, transfusion (see RCOG GTG 47 for obstetric transfusion).
Calcium. Calcium supplementation in populations with low dietary calcium intake reduces the risk of pre-eclampsia and its severity, and is recommended by WHO for such populations. South Africa has historically low dietary calcium intake in many communities, and the NDoH Maternity Guideline incorporates calcium supplementation — this is one of the clearest examples of a nutrition intervention with a hard hypertensive-disease endpoint, and links directly to Pre eclampsia and HELLP and Hypertension in pregnancy. The commonly cited dose is around 1.5–2 g elemental calcium daily in divided doses; flag the precise figure as standard teaching pending the current EML.