Iron status at early pregnancy is associated with infectious respiratory and gastric illness in women receiving routine iron supplementation: the NuPED prospective cohort.

Background: Antenatal iron deficiency (ID) and anaemia, but also elevated ferritin and haemoglobin (Hb) have been associated with morbidity during pregnancy. In South Africa, pregnant women receive routine iron supplementation for anaemia prevention regardless of iron status. Our aim was to assess whether iron status at early pregnancy is associated with infectious morbidity and symptoms during pregnancy.

Methods: This prospective cohort was conducted in 250 pregnant women at a public maternal and child hospital in Johannesburg, South Africa. Biomarkers of maternal iron status at < 18 weeks' gestation were measured. Women kept a symptoms diary throughout pregnancy. Associations were determined using multivariable regression models.

Results: ID women had 2.6 times greater odds for experiencing gastric illness (OR: 2.642, 95% CI: 1.116, 6.255, p = 0.027). Anaemic women (Hb < 10.5 g/dL) tended to have double the duration of respiratory illness [median 15.5 (5.0, 31.0) days] compared to non-anaemic women [median 8.0 (6.0, 12.1) days], (β: 0.167, 95% CI: -0.007, 0.342, p = 0.060) and had more incidences of vomiting throughout pregnancy (p = 0.028). In the partially adjusted models, iron sufficient erythropoiesis (non-IDE) women tended to have 2.3 times increased odds for respiratory illness (OR: 2.314, 95% CI: 0.939, 5.701, p = 0.068) and there were more incidences of fever during pregnancy in the non-IDE group (p = 0.006).

Conclusion: Anaemic and ID pregnant women in this largely overweight population, receiving ~ 55 mg iron daily, experience more and longer infectious morbidity, potentially related to poor iron absorption. However, although presenting with weaker evidence, iron-sufficient erythropoiesis women at early pregnancy receiving the same routine iron supplementation may have twice the risk to contract infectious respiratory illness than IDE women during pregnancy.