Health Blog

Iron Deficiency & Pregnancy


A recent study out of Belgium showed that, based on ferritin levels, approximately 35% of pregnant women in their first trimester were iron deficient. As Dr. Poppe, lead author of the study and Head of Saint-Pierre University Hospital’s Endocrine Clinic, said, “Women should be checked for iron deficiency during pregnancy, and ideally before too.” It may have been surprising to find iron deficiency anemia (IDA) in a wealthy industrialized country, but perhaps it shouldn’t be. Dietary guidelines during the second half of the twentieth century and the early part of the twenty-first included strong recommendations to limit consumption of some of the most iron-rich foods, such as red meat and liver. Pregnant women, specifically, have also long been cautioned to avoid shellfish, another iron heavy-hitter. (There are many marine foods that are safe for pregnancy, including shrimp and crab.)

Iron is available in many plant foods, especially beans and dark green leafy vegetables, but this is non-heme iron, which is less bioavailable and, in the case of beans, may be bound to phytic acid, which makes the iron even less available to the body.

Iron deficiency is common among adolescent females, so it’s not entirely surprising that this would carry over into pregnancy. In fact, without iron supplementation, upwards of 60% of pregnant women may develop IDA during the second half of their pregnancy. Overall, in industrialized countries, the prevalence of iron deficiency during pregnancy is anywhere from 24–44%. This can be disastrous in the long term, as women require higher amounts of iron in order to maintain the increased blood supply to the fetus. Some estimates suggest that iron needs triple during pregnancy.

The recommended dietary allowance (RDA) for iron, as set by the Food and Nutrition Board of the Institute of Medicine of the National Academies of Sciences, is 18mg/day for women of childbearing age, and this jumps to 27mg/day during pregnancy—an amount that may be difficult for some women to reach, particularly if they adhere to vegan or vegetarian diets, as well as if they are omnivores but choose to eat smaller amounts of iron-rich meats.

Iron has a little-known role in thyroid health. It’s required for synthesis of thyroid hormone and proper functioning of thyroid peroxidase, and iron deficiency limits the conversion of T4 to T3 in the liver. The Belgian study concluded that iron deficiency is associated with small but significant increases in thyroid autoimmunity and subclinical hypothyroidism. Suboptimal maternal thyroid function may have profound effects for cognitive function and development in offspring, and while iodine intake is a big factor here, iron also plays a role. With this in mind, might it be possible that maternal iron deficiency, or even just subclinical insufficiency, is playing a role in the increased incidence of conditions that affect learning, attention, and behavior in children these days? Moreover, there seems to be a synergy between iron and iodine, such that targeting iron repletion may increase the efficacy of iodine supplementation.

With the increasing popularity of functional medicine, healthcare practitioners and patients alike are becoming enamored with advanced testing and targeted protocols based on genetic profiles. While these are certainly helpful and represent a leap forward in the use of new technologies to develop highly effective treatments, we shouldn’t discount the tried and true. Sometimes the simple and less glamorous things (such as testing for iron) have the biggest impact, and because they’re simple, they might be overlooked, to the detriment of the patient, as was demonstrated via a case of scurvy in a child that was missed by a slew of doctors and specialists until someone raised questions about the child’s diet.

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