• Posted September 26, 2024

Most Pregnant Women Will Become Iron Deficient, Study Finds

Four out of five pregnant women will become deficient in an essential nutrient, iron, by their third trimester, a new study finds.

The researchers and other experts are now advocating that iron levels be routinely checked during a pregnancy for the safety of a mother and her baby.

Right now, guidelines from the United States Preventive Services Taskforce (USPSTF), an influential independent panel of medical experts, and the American College of Obstetricians and Gynecologists (ACOG) do not advocate for regular iron checks.

However, the new findings suggest that both groups should “change their approach to diagnosis to screen all pregnant women for iron deficiency, irrespective of the presence or absence of anemia, and recommend supplementation when present for the most frequent nutrient deficiency disorder that we encounter," wrote the authors of an editorial accompanying the new study.

The findings were published Sept. 26 in the American Journal of Clinical Nutrition.

The new research was led by Dr. Elaine McCarthy, a lecturer in nutrition at the School of Food and Nutritional Sciences at University College Cork, in Ireland.

Her team noted that pregnancy brings on a 10-fold surge in uptake of dietary iron to supply the needs of both the fetus and the mom-to-be.

A woman's bodily "iron stores" at the beginning of her pregnancy can help supply much of this needed iron, but McCarthy's team note that an estimated 50% of women begin pregnancy with insufficient iron stores.

Depleted iron levels can, in the worst-case scenario, lead to anemia, which has long been tied to a heightened risk for postpartum depression, postpartum hemorrhage, preterm birth, low birth weight and small-for-gestational age birth. 

However, iron levels in pregnancy that are low but do not meet the threshold for anemia can still be hazardous, being linked to later neurodevelopmental issues for offspring.

In the United States, there's no set rule to test for iron levels in pregnancy in the absence of anemia. The USPSTF, for example, states that evidence is still "insufficient" to mandate such testing.

That's in contrast to guidelines from the International Federation of Gynecology and Obstetrics and European Hematology Society, which both advocate for routine tests in a woman's first trimester, regardless of whether she is anemic or not.

Just how prevalent is iron deficiency in pregnancy?

To find out, McCarthy's team tracked blood levels of the nutrient in 641 Irish women who were pregnant and had a successful delivery for the first time.

Testing was done at 15 weeks, 20 weeks and 33 weeks of pregnancy.

“In this high-resource setting,” the researchers found that “iron deficiency defined by a variety of biomarkers and thresholds, was very common during pregnancy, despite the cohort profile as generally healthy.” 

Deficiencies tended to appear later in pregnancies: While none of these relatively well-off, well-cared-for women were iron-deficient in their first trimester, by their third trimester 80% had insufficient levels of iron.

However, "iron-containing supplements [mainly multivitamins] taken pre/early pregnancy were associated with a reduced risk of deficiency throughout pregnancy, including the third trimester," McCarthy and colleagues noted. Supplements typically contained a daily 15-17 milligram (mg) dose of iron.

They also noted that iron deficiency blood screening should be based on two markers of iron levels, hemoglobin and ferritin, not just hemoglobin alone. Ferritin is a protein that stores iron.

The researchers suggest that a blood level of 60 micrograms per liter or less of ferritin at 15 weeks gestation be the cutoff for signaling the potential for iron deficiency.

"This has previously been identified as the inflection point at which fetal iron accretion is compromised, leading to poorer neurocognitive function and earlier onset of postnatal iron deficiency in the offspring," McCarthy's team said.

The accompanying journal editorial was co-authored by Dr. Michael Auerbach, a clinical professor of medicine at Georgetown University in Washington, D.C., and Dr. Helain Landy, chair of obstetrics and gynecology at Georgetown.

Based on the new findings, they are urging both the USPSTF and ACOG to change guidelines and mandate routine iron deficiency testing -- even in the absence of anemia -- for all pregnant women.

More information

Find out more about iron levels in pregnancy at the Mayo Clinic.

SOURCE: American Society for Nutrition, news release, Sept, 26, 2024