Maternal iron deficiency anaemia is treated as a number to correct rather than as a risk to track, and the follow-up haemoglobin is often never checked. This analysis shows what that costs.
It is a secondary analysis of a multicentre randomised trial in India comparing single-dose intravenous ferric derisomaltose, single-dose intravenous ferric carboxymaltose and oral iron for moderate iron deficiency anaemia — haemoglobin 7.0 to 9.9 g/dL — started at 14 to 17 weeks of gestation. A total of 4,252 women were included, roughly 1,400 in each arm. The predictors were haemoglobin, ferritin and transferrin saturation at 20 to 24 weeks; the outcome was stillbirth, with early preterm birth and small-for-gestational-age as secondary.
Each 1 g/dL increase in haemoglobin response by 20 to 24 weeks was associated with a lower risk of stillbirth (relative risk 0.74, 95% CI 0.56 to 0.98), adjusted for age, body mass index, parity, treatment arm, baseline haemoglobin and site. Modelling the relationship as non-linear, stillbirth risk rose progressively as haemoglobin fell below 10.5 g/dL (p<0.0001), as did early preterm birth before 34 weeks (p=0.01).
That 10.5 g/dL figure is the practical output. It is not a treatment target invented by consensus; it is where the risk curve begins to climb in a population of women who have all already been treated for anaemia.
This is Indian data in Indian women, and anaemia in pregnancy is the single most common antenatal problem in the country. The change it implies is small and entirely achievable: check the haemoglobin again at 20 to 24 weeks, and treat a persistent value below 10.5 as a failure of the first treatment rather than as expected.
- Recheck haemoglobin at 20 to 24 weeks in every woman treated for anaemia — the response, not the starting value, predicts outcome
- Treat a haemoglobin still below 10.5 g/dL at 20 to 24 weeks as treatment failure and escalate
- Escalation means intravenous iron where oral iron has not worked, plus investigation of why it has not
- Ask about adherence and gastrointestinal side effects before assuming oral iron has failed pharmacologically
- Flag persistent mid-pregnancy anaemia in the notes as a stillbirth and early preterm risk factor, not just a laboratory value
The statistics, in plain English
The linear result, relative risk 0.74 with an interval of 0.56 to 0.98, only just excludes 1.0 — so the direction is established but the size is imprecise. The quadratic modelling is the more informative part: fitting a curve rather than a straight line lets the analysis show that risk is flat across the normal range and rises steeply below a threshold, which is how most nutrient-outcome relationships actually behave. Two cautions. This is a secondary analysis of a trial designed to compare treatments, so the haemoglobin-outcome relationship is observational within a randomised trial, and women who respond poorly to iron may differ in ways adjustment cannot capture. And an association between a mid-pregnancy haemoglobin and stillbirth does not prove that raising it prevents stillbirth — the authors call explicitly for a trial to test that.
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