4 in 5 Pregnant Women Become Iron Deficient: ‘Staggering’ Says Doctor

The vast majority of pregnant women develop an iron deficiency by their third trimester, according to a study that hematologist Dr. Michael Auerbach, of Georgetown University School of Medicine, has called “a bombshell.”

“Imagine the staggering numbers from McCarthy et al. [the study authors]: iron deficiency in 21 percent at 15 weeks, 47 percent at 20 weeks and 83 percent at 33 weeks. All these women are missed!” he told Newsweek. “I can assure you, if men had periods and babies, this would have been fixed a century or more ago.”

During pregnancy, a woman’s requirement for iron increases almost tenfold, as her body tries to support itself and the needs of a growing baby. Not enough iron, and both mother and child can be negatively affected.

“Maternal iron deficiency is associated with adverse pregnancy outcomes, including low birthweight, prematurity, and intrauterine growth restriction,” Professor Susan Fairweather-Tait, of Norwich Medical School, England, told Newsweek.

Auerbach added that iron was essential for the healthy development of the child, with effects measurable “up to 19 years of age and likely longer” on brain health and motor function.

“This has an effect on fetal development,” he said. “Forty five percent of infants [in the U.S.] are born with iron levels consistent with developmental delay. We don’t even check [their mothers for iron deficiency].”

So, scientists at the American Society for Nutrition decided to investigate iron levels during pregnancy, in one of the largest studies ever to do so, according to the paper.

They used data from 641 women in Ireland—the vast majority Caucasian and Irish—who became pregnant and successfully delivered children while participating in the Improved Pregnancy Outcomes via Early Detection consortium project.

None of these women were anemic at the start of the study. That means, none of them had iron levels low enough to affect the hemoglobin in their blood, which is a common way iron deficiency is tested.

Blood samples were taken at 15 weeks, 20 weeks and 33 weeks of pregnancy, and scientists found that one in five women were iron deficient in their first trimester, two in five at the second trimester, and four in five at the third trimester.

This was despite the fact that three quarters of the women took iron-containing supplements during pregnancy—although the scientists did note that those who supplemented were 57 percent less likely to experience a deficiency.

“The main message is that all women of reproductive age, and all women who are pregnant, need to be screened for higher deficiency, whether they’re anemic or not,” said Auerbach, who co-wrote the study’s editorial introduction with Dr. Helain Landy, from the Department of Obstetrics and Gynecology at Georgetown.

“Look at the numbers of these people who were missed,” said Auerbach. “These were healthy Irish women from a high resource group of people, nonanemic and asymptomatic. Look at these numbers. These are staggering: 83 percent at 33 weeks.”

The study authors criticized current U.S. guidelines for iron screening, calling for an update to recommendations that Auerbach and Landy described as “misogynistic,” as they normalize “the morbid event of iron deficiency”.

The International Federation of Gynecology and Obstetrics, and the European Hematology Society, have both recommended that all pregnant and reproductive-age women be screened for iron, even if they don’t have anemia—but the United States Preventive Services Taskforce has continued to disagree, citing “insufficient” evidence.

Yet this study found that low levels of ferritin—a protein that stores iron—in women in the first trimester could predict iron deficiency by the third trimester, so early screening could catch low iron levels before they became dangerous.

To protect against iron deficiency in pregnancy, Fairweather-Tait recommended “eating a diet containing a good supply of bioavailable iron” including meat, fish, poultry, dark green vegetables, and sources of vitamin C such as citrus fruits.

“If this is not enough, the solution is to take iron supplements—preferably low-dose and taken every other day.”

But Auerbach told Newsweek that oral iron supplements were not enough to address this problem, citing evidence that “up to 75 percent of pregnant women who are given oral iron can’t stand it”.

He said that oral iron supplements often led to, or worsened, constipation—already a problem for many women in pregnancy—as well as other side effects, including nausea.

Auerbach recommended intravenous iron supplementation, where iron is injected, as a highly effective and “incredibly safe” method.

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Reference

McCarthy, E. K., Schneck, D., Basu, S., Xenopoulos-Oddsson, A., McCarthy, F. P., Kiely, M. E., Georgieff, M. K. (2024). Longitudinal evaluation of iron status during pregnancy: a prospective cohort study in a high-resource setting, The American Journal of Clinical Nutrition. https://doi.org/10.1016/j.ajcnut.2024.08.010

Auerbach, M., Landy, H. (2024). Finally, a quality prospective study to support a proactive paradigm in anemia of pregnancy, The American Journal of Clinical Nutrition. https://doi.org/10.1016/j.ajcnut.2024.08.010