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-risks 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.
Iodine, vitamin D and others. Iodine is essential for fetal neurodevelopment; SA uses universal salt iodisation as the population strategy, with supplementation considered where deficiency is likely. Vitamin D deficiency is common; routine universal high-dose supplementation is not uniformly recommended, and guidance varies — be cautious and individualise. Note the harm of excess: high-dose preformed vitamin A (retinol) is teratogenic and should be avoided, which is why generic high-strength multivitamins and liver in large quantities are discouraged.
Aspirin — the supplement that is really a drug
Low-dose aspirin straddles "supplement" and "pharmacotherapy" and is too important to omit. For women at risk of pre-eclampsia, low-dose aspirin (commonly 75–150 mg daily) started from around 12 weeks reduces the incidence of pre-eclampsia and preterm pre-eclampsia (NICE NG133). This is a high-yield intervention you should be initiating at booking for the right women — covered in depth in pre-eclampsia-and-hellp — and it is a far higher-impact "tablet to start" than most of the micronutrients.
Figure I5.1 — Time folate, iron, calcium and aspirin to the correct pregnancy risk, while avoiding high-dose retinol and other excess supplementation.
Gestational weight gain
Weight gain in pregnancy is best understood as a U-shaped risk curve anchored on the pre-pregnancy (or early-booking) BMI. Too little gain is associated with fetal growth restriction and preterm birth; too much is associated with macrosomia, gestational diabetes, pre-eclampsia, caesarean delivery, and postpartum weight retention that seeds obesity for the next pregnancy. The most widely taught framework is the Institute of Medicine (now National Academy of Medicine) BMI-stratified ranges — present these as the standard reference framework rather than a SA guideline mandate:
| Pre-pregnancy BMI (kg/m²) | Category | Commonly taught total gain (singleton) |
|---|---|---|
| < 18.5 | Underweight | ~12.5–18 kg |
| 18.5–24.9 | Normal | ~11.5–16 kg |
| 25.0–29.9 | Overweight | ~7–11.5 kg |
| ≥ 30.0 | Obese | ~5–9 kg |
These IOM figures are textbook standard, not a verified SA NDoH threshold — flag accordingly. In the SA context the obesity end of the curve dominates clinically: maternal obesity (RCOG GTG 72) raises risks of gestational diabetes, hypertensive disease, thromboembolism, fetal macrosomia and stillbirth, difficult monitoring and operative delivery, and worse anaesthetic risk. The corollary in food-insecure populations is inadequate gain and growth restriction — the same antenatal visit may demand opposite advice depending on the woman in front of you.
Exercise
Physical activity in pregnancy is safe and beneficial for the large majority of women, and a sedentary default is not the safe option. Regular moderate-intensity aerobic and strengthening activity reduces excessive gestational weight gain, lowers the incidence of gestational diabetes and hypertensive disorders, improves mood and may ease labour. International guidance (broadly reflected in NICE NG201 antenatal-care lifestyle advice) endorses continuing or commencing moderate exercise — the commonly taught target is around 150 minutes of moderate activity per week, which is a population physical-activity figure rather than a pregnancy-specific verified threshold, so present it as such. Pelvic-floor muscle training is a specific, evidence-supported component. Counsel women to avoid activities with a high fall or abdominal-trauma risk (contact sports, horse-riding), scuba diving (fetal decompression risk), and supine exercise late in pregnancy (aortocaval compression), and to maintain hydration and avoid overheating.
Assessment
History
- Diet and food security: usual intake, affordability, who controls food in the household, religious/cultural restrictions, vegetarian/vegan status (B12, iron, omega-3), pica.
- Pre-pregnancy weight and BMI, weight trajectory, prior gestational diabetes or macrosomic infant.
- Supplement and medication use: is she taking folate already, since when, and the dose? Over-the-counter multivitamins (retinol content), traditional/herbal remedies — ask explicitly and non-judgementally.
- Risk factors that change supplementation: previous NTD, diabetes, anti-epileptic drugs, obesity, malabsorption, HIV and ART regimen.
- Symptoms of deficiency or excess: fatigue/pallor (anaemia), and conversely symptoms suggesting hyperemesis limiting intake (see RCOG GTG 69) where nutrition becomes acute.
- Activity level: current exercise, occupation (physical demand, standing), and any obstetric contraindication to exercise.
Examination
- BMI from booking weight and height; serial weight at subsequent visits interpreted against the BMI-appropriate range, not in isolation.
- Pallor, glossitis, koilonychia (iron); goitre (iodine); signs of oedema in context.
- Symphysis–fundal height tracking — the clinical proxy that links nutritional adequacy to fetal growth; discordance triggers the growth-restriction pathway of intrauterine-growth-restriction and review of placental-insufficiency-response.
Investigations
- Haemoglobin / full blood count at booking and repeated per schedule; iron studies (ferritin) if anaemia is confirmed and the picture is unclear.
- HIV testing as routine SA practice (opt-out), because HIV and its treatment intersect with anaemia, micronutrient status and folate dosing — see hiv-in-pregnancy.
- Random/booking glucose or risk-based screening for gestational diabetes where weight and risk factors warrant (NICE NG3), since weight gain and GDM are tightly coupled.
- Targeted tests only where indicated (e.g. vitamin D, B12) — there is no role for indiscriminate micronutrient panels.
Management
Management here is overwhelmingly counselling, prescribing and monitoring, delivered longitudinally across antenatal contacts. Structure it.
Universal advice for every pregnant woman
- Start/continue folic acid periconceptionally and through the first trimester; the higher 5 mg dose for the high-risk groups above (confirm the exact dose against the current NDoH/EML).
- Routine iron + folate supplementation per SA NDoH policy; escalate investigation and treatment for confirmed anaemia and treat it as a haemorrhage-reserve issue, not a cosmetic blood result.
- Calcium supplementation in this low-dietary-calcium population for its pre-eclampsia benefit (WHO recommendation, incorporated by NDoH).
- Low-dose aspirin from ~12 weeks for women at risk of pre-eclampsia (NICE NG133) — assessed and started at booking.
- Dietary counselling: a varied diet with adequate protein, iron-rich foods (and vitamin-C co-ingestion to aid absorption), calcium sources, and folate-rich vegetables; realistic and affordable within her means.
- Food-safety advice: avoid unpasteurised dairy and soft cheeses, undercooked meat, raw eggs and high-mercury fish (listeriosis, toxoplasmosis, salmonella, mercury); avoid liver/high-dose retinol; wash produce.
- Caffeine moderation, no alcohol (no safe threshold — links to substance-use-in-pregnancy), and smoking cessation.
- Exercise: encourage continuation/commencement of moderate activity and pelvic-floor exercises, with the safety caveats above; reassure that it does not cause miscarriage in normal pregnancy.
Tailoring to the woman
- Underweight / food-insecure: prioritise caloric and protein adequacy, link to social support and nutrition programmes, monitor SFH closely for growth restriction, and gain toward the higher end of her BMI band.
- Overweight / obese (RCOG GTG 72): target the lower gestational-weight-gain range, screen for and manage GDM and hypertensive disease proactively, consider VTE risk assessment, counsel on the anaesthetic and intrapartum implications, and avoid the trap of recommending active weight loss in pregnancy — the goal is limiting excess gain, not dieting.
- HIV-positive: integrate ART (TLD per SA ART guidelines), be alert to interacting micronutrient/anaemia issues and to folate dosing where relevant, and manage within the broader plan of hiv-in-pregnancy.
- Hyperemesis / intractable vomiting: when nutrition fails acutely, this becomes a management problem in its own right (rehydration, thiamine before glucose, antiemetics) per RCOG GTG 69 — do not let a "nutrition" objective blind you to the emergency overleaf.
Levels of care and follow-up
Most nutritional management is delivered at primary/community level by midwives, with escalation to district/regional level for complications (severe anaemia needing parenteral iron or transfusion, poorly controlled GDM, hypertensive disease, significant growth restriction). The loop is closed by serial weight, Hb checks and SFH plotting, with documented advice and supplement adherence at each visit.
Emergency overlap — anaemia and haemorrhage
Although nutrition is mostly outpatient, recognise the one place it turns acute: the severely anaemic woman who bleeds. A woman booking with Hb already low has minimal reserve, and a postpartum haemorrhage will decompensate her fast.
Drill — severe anaemia presenting with active obstetric bleeding: call for help and activate the obstetric haemorrhage protocol; two large-bore IV cannulae; FBC, cross-match, coagulation; resuscitate with warmed crystalloid and blood early (do not wait for a "trigger" Hb in active bleeding); treat the cause of bleeding in parallel (uterotonics/tranexamic acid 1 g IV within 3 h per WOMAN trial — see postpartum-haemorrhage); transfuse per RCOG GTG 47. The antenatal lesson is upstream: never let a woman reach labour with untreated anaemia when months of iron would have given her reserve.
Red flags / pitfalls
- Treating folate as optional or starting it late. NTDs close before most women present; the win is periconceptional. Always ask whether she was already taking it and identify the high-risk women who need the higher dose.
- Ignoring anaemia as "just dilutional". Distinguish physiological dilution from true iron deficiency; untreated anaemia is a Saving Mothers–flagged aggravator of maternal death via reduced haemorrhage reserve.
- One-size-fits-all weight advice. The same clinic sees food-insecure underweight women and obese women on the same morning; the correct advice is opposite. Anchor on BMI, not on a single "gain target".
- Recommending weight loss in pregnancy. The aim in obesity is to limit excess gain, not to diet — active caloric restriction risks the fetus.
- Over-supplementation and retinol teratogenicity. High-dose vitamin A and indiscriminate multivitamins can harm; more is not better. Never silently substitute a high-strength generic multivitamin for a pregnancy-appropriate one.
- Quoting precise thresholds you have not verified. Anaemia cut-offs, exact folate/calcium doses and IOM ranges are repeated here as standard teaching — confirm the operative numbers against the current SA NDoH Maternity Guideline (2024) and EML before you prescribe.
- Forgetting aspirin. The highest-impact "tablet" in this whole domain for at-risk women is low-dose aspirin from 12 weeks — easy to omit when the mental frame is "nutrition".
- Discouraging exercise out of misplaced caution. For uncomplicated pregnancy, sedentary behaviour is the riskier default; reassure and encourage within sensible limits.
Evidence anchors
- South African National Integrated Maternal and Perinatal Care Guideline (NDoH, 2024) — the SA obstetric source of truth for routine supplementation (folate, iron, calcium), anaemia management and antenatal lifestyle advice.
- Saving Mothers / NCCEMD reports (latest triennium) — anaemia as an aggravating factor in maternal deaths; haemorrhage and hypertension as leading causes, framing why iron and calcium matter.
- South African EML — Hospital and Primary Care levels (current edition) — for the operative doses of folic acid, iron, calcium and aspirin.
- South African National HIV / ART Consolidated Guidelines (2023) — TLD first-line; relevance to anaemia, micronutrients and folate dosing in pregnancy.
- NICE NG201 — Antenatal care (2021) — routine supplementation, dietary and lifestyle (including exercise) counselling, food-safety advice.
- NICE NG133 — Hypertension in pregnancy (2019) — low-dose aspirin from ~12 weeks for women at risk of pre-eclampsia.
- NICE NG3 — Diabetes in pregnancy — screening and management of gestational diabetes, tightly coupled to weight gain.
- RCOG GTG 72 — Obesity in pregnancy — risks and antenatal management of the obese gravida.
- RCOG GTG 69 — Hyperemesis gravidarum — when nutrition fails acutely.
- RCOG GTG 47 — Blood transfusions in obstetrics — transfusion in severe anaemia/haemorrhage.
- WOMAN trial (Lancet 2017) — tranexamic acid 1 g IV within 3 h in PPH (haemorrhage-reserve link).
- Institute of Medicine / National Academy of Medicine gestational weight gain ranges — the standard BMI-stratified reference framework (textbook standard, not a SA NDoH mandate).
- Note: physiological energy increments, exact anaemia trimester cut-offs, folate (0.4 mg / 5 mg) and calcium (1.5–2 g) doses, and the 150-minutes-per-week activity figure are stated as standard teaching and should be confirmed against the current NDoH guideline / EML before clinical use.