The Effect of Oral Iron Supplementation on the Glucose Metabolism in Non-Anemic Pregnant Women: A Prospective Case-Control Study

In this prospective case-control study, we assessed the effect of oral iron supplementation on glucose metabolism of pregnant women who had low risk of gestational diabetes mellitus (GDM). Between April 2004 and November 2004, we analyzed pregnant women that were admitted to our antenatal clinic at their first trimester. Study group was given at least 2 months of oral iron supplementation (40 mg/day) after entering study protocol. Control group was not given any iron supplementation, but matched with study group according to age, gravida, parity, BMI, first trimester Hb. In these two groups, 50 g oral glucose tolerance test (OGTT) at the 24th-28th weeks and iron metabolism parameters were compared. This study was approved by our institutional review board. Fifty-eight eligible women (35 study, 23 control) were analyzed. Mean ferritin levels at 24-28th weeks were 12.5 +/- 9.7 ng/ml in control, and 16.5 +/- 6.09 ng/ml in study group (p=0.018). The mean serum glucose levels after 50 g OGTT were 115.26 +/- 27.01 mg/dl in control group, and 129.77 +/- 27.8 mg/dl in study group (p=0.04). 50 g OGTT was considered as abnormal in 17 pregnant women (49%) in the study group and 6 (26%) in the control group (P=0.05). This is the first prospective trial in the literature that evaluated the relationship between iron supplementation and glucose intolerance in pregnant women. We found that iron overloading, might cause glucose intolerance in non-anemic pregnant women who had a low-risk for GDM. Thus, the rationale of routine iron supplementation should be discussed especially in non-anemic women at risk of developing GDM in the absence of any potential benefit to the fetus.