A new study from Oregon Health & Science University, supported by the Agency for Healthcare Research and Quality at the U.S. Department of Health and Human Services, finds that while routine prenatal iron supplementation reduces the incidence of iron deficiency and related anemia during pregnancy, there is no significant effect on maternal or infant health outcomes, such as maternal hypertension and preterm birth.
This means for the average pregnancy, additional iron supplementation — which can cause nausea and constipation — may not be necessary.
The study, published today in the journal JAMA Network Open, will inform new recommendations by the U.S. Preventive Services Task Force, a group supported by the federal Agency for Healthcare Research and Quality to make evidence-based recommendations about clinical preventive services.
"There's a lot of marketing out there targeting various vitamins and supplements for pregnant people, and it can be overwhelming," said Amy G. Cantor, M.D., M.P.H., professor of medical informatics and clinical epidemiology, family medicine and obstetrics and gynecology in the OHSU School of Medicine, and the study's corresponding author. "It's best to keep it simple: If you don't have any risk factors outlined by your clinician, then a standard prenatal vitamin should be sufficient to ensure a healthy pregnancy."
Due in part to higher blood volume and physical changes during pregnancy, iron deficiency is the most common cause of anemia, a condition in which there are lower levels of healthy red blood cells available to carry oxygen throughout the body, sometimes resulting in symptoms such as fatigue or shortness of breath.
In the United States, nearly 18% of pregnant people are iron deficient; 5% of those, 5% have an iron deficiency that leads to anemia. The condition has a greater prevalence in certain populations, including Black and Mexican American individuals, as well as those at lower income levels who may not have ready access to iron-rich foods.
Screening for iron deficiency in pregnancy is common and may lead to early identification and treatment. However, evidence on the relationship between iron status and perinatal health outcomes is limited.
"Clinically, the question we wanted to address was if iron supplementation improves maternal and infant health outcomes, and there was actually very limited evidence in both of these areas," Cantor said. "We hope clinicians can use this information to improve discussions with patients around symptoms and health history, so treatment can be optimized and tailored to the individual."
Individualized iron, prenatal care
In 2015 the U.S. Preventive Services Task Force, or USPSTF, found insufficient evidence to assess the balance of benefits and harms of routine screening and supplementation for iron deficiency during pregnancy. In their new study, OHSU researchers aimed to inform updated recommendations for routine screening and supplementation by the USPSTF.
In a systematic review that looked at 17 trials on maternal iron supplementation, researchers found that when supplementation was compared with placebo or no supplementation, there were no statistically significant differences in health outcomes immediately before and after birth for parent or baby. The outcomes researchers examined included maternal quality of life, rates of gestational diabetes, maternal hemorrhage, hypertensive disorders of pregnancy, cesarean delivery, preterm birth and infant low birth weight.
While there are few harms of iron supplementation, there can be short-lived gastrointestinal side effects such as nausea or constipation; these side effects can be uncomfortable and disruptive for patients, especially when compounded with additional symptoms of pregnancy.
Given the limited impact on maternal and infant health outcomes, clinicians can use these findings to inform decisions around whether pregnant patients should take iron supplements along with their prenatal vitamins, based on their own personal history and symptoms. Iron is often included in many prenatal vitamins but can also be absorbed from common foods like lean meat and seafood, spinach, and certain legumes like white and kidney beans.
Cantor notes these findings address asymptomatic, average-risk pregnant people and do not apply to those with severe symptoms of iron deficiency, as measured by blood tests. Looking forward, she says more research is needed to understand the association between changes in maternal iron status and health outcomes.
"What this reinforces is that prenatal care should be individualized, because each patient is unique and how they experience pregnancy will also be unique," Cantor said. "Prenatal care shouldn't be one-size-fits-all, and we hope this review sparks more individualized discussions between patients and providers about health during pregnancy."
This research was funded under AHRQ Contract No. 75Q80120D00006, Task Order No. 75Q80121F32009, from the Agency for Healthcare Research and Quality (AHRQ), US Department of Health and Human Services, under a contract to support the USPSTF.
