Iron supplement in pregnancy and development of gestational diabetes—a randomised placebo‐controlled trial

Abstract

Objective To test the hypothesis that iron supplement from early pregnancy would increase the risk of gestational diabetes mellitus (GDM).Design Randomised placebo-controlled trial.Setting A university teaching hospital in Hong Kong.Population One thousand one hundred sixty-four women with singleton pregnancy at less than 16 weeks of gestation with haemoglobin (Hb) level between 8 and 14 g/dl and no pre-existing diabetes or haemoglobinopathies.Methods Women were randomly allocated to receive 60 mg of iron supplement daily (n = 565) or placebo (n = 599). Oral glucose tolerance tests (OGTTs) were performed at 28 and 36 weeks. Women were followed up until delivery.Outcome measures The primary outcome was development of GDM at 28 weeks. The secondary outcomes were 2-hour post-OGTT glucose levels, development of GDM at 36 weeks and delivery and infant outcomes.Results There was no significant difference in the incidence of GDM in the iron supplement and placebo groups at 28 weeks (OR: 1.04, 95% confidence interval [CI]: 0.7-1.53 at 90% power) or 36 weeks. Maternal Hb and ferritin levels were higher in the iron supplement group at delivery (P < 0.001 and P = 0.003, respectively). Elective caesarean section rate was lower in the iron supplement group (OR: 0.58, 95% CI: 0.37-0.89). Infant birthweight was heavier (P = 0.001), and there were fewer smallfor-gestational-age babies in the iron supplement group (OR: 0.46, 95% CI: 0.24-0.85).Conclusion Iron supplement from early pregnancy does not increase the risk of GDM. It may have benefits in terms of pregnancy outcomes.

Dietary iron intake, iron status, and gestational diabetes

“…The majority of iron supplements contain nonheme iron in the form of ferrous and ferric iron salts, such as ferrous sulfate, ferric sulfate, and ferrous fumarate (18,40). The effects of iron supplementation on the risk of GDM have been examined in 2 large randomized control trials (34,36) (Table 1). In the trial conducted in Hong Kong (34), either an iron supplement (300 mg ferrous sulfate tablet containing 60 mg elemental Fe) or a placebo tablet was prescribed to women with hemoglobin concentrations within the usual range [i.e., those who had either low (,8 g/dL) or high (.14 g/dL) hemoglobin concentrations at a baseline of ,16 wk of gestation were excluded].…”

“…The effects of iron supplementation on the risk of GDM have been examined in 2 large randomized control trials (34,36) (Table 1). In the trial conducted in Hong Kong (34), either an iron supplement (300 mg ferrous sulfate tablet containing 60 mg elemental Fe) or a placebo tablet was prescribed to women with hemoglobin concentrations within the usual range [i.e., those who had either low (,8 g/dL) or high (.14 g/dL) hemoglobin concentrations at a baseline of ,16 wk of gestation were excluded]. No effect of iron supplementation was observed on the risk of GDM (RR: 1.04; 95% CI: 0.70, 1.53), yet inference from these findings was limited by low compliance (54.4%) and the exclusion of women with an elevated iron status at baseline.…”

Iron Deficiency and Anaemia in Pregnant Women in Malaysia ? Still a Significant and Challenging Health Problem

“…Furthermore, IDA in late third trimester significantly increases the risk of complications at delivery as well as the risk for maternal perinatal death [26].…”

“…In severe anaemia, maternal death may occur in the last trimester, during labour, immediately after delivery and during puerperium due to cardiac failure or pulmonary embolism [53]. Anaemia in association with delivery increases the frequency of birth complications [2,3,26]. Therefore, a reduction in the prevalence of prepartum and postpartum anaemia will also reduce maternal mortality rate.…”

Role of Iron Supplements on Pregnancy Outcomes

“…It is very vital to have a good amount of iron reserves and iron supplements before pregnancy as absorbed iron needs cannot be fulfilled at that pregnancy from just food iron or iron supplementation during pregnancy. 1 A healthier and better lifestyle is observed if pregnant women with anemia are treated by iron supplements. 2 Comparing the delivery status of anemic and nonanemic women, we come to see that anemic women tend to have a higher risk of pre-term delivery.…”