Are iron supplements appropriate for iron replete pregnant women?
Introduction
Among the remarkable profusion of metabolic alterations during normal pregnancy is the upregulation of dietary iron absorption in the second and third trimesters [1]. During the first 12 weeks, the normal daily dietary intake of 1–1.5 mg remains constant, whereas during the second trimester, iron absorption increases to 5 mg and, in the third trimester, to 9 mg.
The increase in absorption, which promptly recedes after parturition, is a well programmed, consistent process rather than an emergency response to a non-existent anemia. In fact, in the US, 88% of 12–47 yr women are iron replete [2]. Moreover, the diets of most iron replete women contain more than an adequate amount of the metal for the entire pregnancy. Nonetheless, iron supplements often are routinely recommended for healthy, iron replete pregnant women. The US Centers for Disease Control and Prevention has advised a supplement of 30 mg iron/day for all pregnant persons [3]. A similar recommendation is that iron replete pregnant women whose serum ferritin values are between 30 and 70 ng/ml take 40 mg iron/day [4].
An extensive review of controlled trials failed to demonstrate that daily iron supplementation of iron replete women improves clinical outcome of either the mother or newborn [5]. However, it has long been assumed that daily iron loading of iron replete persons is harmless to both mother and fetus. But more recently, two hazardous complications of pregnancy, gestational diabetes mellitus (GDM) and pre-eclampsia, have been recognized to be associated with elevated body iron values. Moreover, for pre-eclampsia, the danger may extend not only to the fetus but also to maternal health long after the pregnancy has been completed [6].
Section snippets
Gestational diabetes
During the past score of years, an array of clinical and epidemiological studies have reported a positive association between elevated body iron and development of type 1 and type 2 diabetes, other insulin resistant states such as metabolic syndrome, and gestational diabetes [7]. Anti-oxidative defense mechanisms of pancreatic beta cells are particularly weak and are readily overwhelmed by iron catalysis of reactive hydroxyl radicals [8]. Animal model studies have confirmed and extended these
Pre-eclampsia
Pre-eclampsia causes maternal vascular endothelial cell dysfunction and fetal growth restriction [14]. It is identified by proteinuria and hypertension. The condition occurs in 3–10% of pregnancies and causes about 15% of pre-term births. In developed countries, pre-eclampsia is the leading cause of maternal mortality and is associated with a five-fold increase in perinatal mortality.
After an episode of pre-eclampsia, women have an increased risk of vascular disease. In a meta-analysis of
Perspectives
Clearly, iron replete women who have had episode(s) of GDM or pre-eclampsia in earlier pregnancies should be counseled to avoid iron supplements. Should this advice be extended to persons in their first pregnancy, especially to those who have inherited mutations associated with iron loading? Should a serum ferritin value be obtained from every patient at the first prenatal visit to a health care provider? The test result would permit evidence-based medical guidance to replace mass medication of
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