Amy Kanter, MD, MPH, holds an iron supplement. To inform clinical recommendations for pregnant patients, Kanter and her OHSU research team investigated the relationship between iron supplements and perinatal health outcomes. (OHSU/Kristin Torres-Hicks)
A new study from Oregon Health & Science University, supported by the U.S. Department of Health and Human Services' Agency for Healthcare Research and Quality, finds that regular prenatal iron supplementation reduces the incidence of iron deficiency and related anemia during pregnancy but has no significant effect on maternal or infant health outcomes, such as maternal hypertension or preterm birth.
This means that during the average pregnancy, additional iron supplements, which can cause nausea and constipation, may not be necessary.
The study, published today in JAMA Network Open, forms the basis for new recommendations from the U.S. Preventive Services Task Force, which is supported by the federal Agency for Healthcare Research and Quality to develop evidence-based recommendations for clinical preventive services.
“There's a lot of marketing targeted at different vitamins and supplements aimed at pregnant women, and it can be overwhelming,” says Amy G. Cantor, MD, MPH, professor of health informatics and clinical epidemiology, family medicine and obstetrics and gynecology at the Oregon Health & Science University School of Medicine and corresponding author of the study. “It's best to keep it simple. If your clinician hasn't identified any risk factors, a standard prenatal vitamin can help ensure a healthy pregnancy.”
Due in part to increased blood volume and physical changes during pregnancy, iron deficiency is the most common cause of anemia, a condition in which there are fewer healthy red blood cells that carry oxygen throughout the body, which can lead to symptoms like fatigue and shortness of breath.
In the United States, about 18% of pregnant women are iron deficient, and 5% of those have iron deficiency that leads to anemia. The condition is more prevalent in certain populations, including Black and Mexican-American people, as well as low-income people who don't have easy access to iron-rich foods.
Screening for iron deficiency during pregnancy is common and can lead to early detection and treatment, but evidence on the relationship between iron status and perinatal health outcomes is limited.
“Clinically, the question we wanted to answer was whether iron supplementation improves the health of mothers and infants, but the evidence in these two areas has actually been very limited,” Kanter says. “We hope that clinicians can use this information to improve discussions with patients about symptoms and health histories, so they can optimize and tailor treatment to the individual.”
Individualized iron, prenatal care
In 2015, the U.S. Preventive Services Task Force (USPSTF) determined that there was insufficient evidence to assess the balance of benefits and harms of routine testing and supplementation for iron deficiency during pregnancy. In a new study, OHSU researchers aimed to inform the USPSTF's updated recommendations on routine testing and supplementation.
In a systematic review that looked at 17 trials of maternal iron supplementation, researchers found that when iron supplementation was compared with a placebo or no supplementation, there were no statistically significant differences in the health of parents or babies immediately before and after birth. Outcomes they looked at included maternal quality of life, gestational diabetes, maternal bleeding, pregnancy-induced hypertension, cesarean section, preterm birth, and rates of low birth weight babies.
Although iron supplementation is unlikely to cause any harm, it can cause temporary gastrointestinal side effects such as nausea and constipation. These side effects can be unpleasant and disruptive to patients, especially when combined with additional symptoms of pregnancy.
Because the impact on maternal and infant health is limited, clinicians can use these findings to help decide whether pregnant women should take iron supplements with their prenatal vitamins, based on their own medical history and symptoms. Iron is included in many prenatal vitamins, but it can also be absorbed from common foods such as red meat, seafood, spinach, and certain legumes, such as white beans and kidney beans.
Kanter points out that these findings were based on asymptomatic, average-risk pregnant women, and don't generalize to women with severe iron deficiency symptoms measured by blood tests. More research is needed to understand the link between changes in maternal iron status and health outcomes, she says.
“This study highlights that prenatal care should be individualized because every patient is different and every pregnancy experience is different,” Kanter said. “Prenatal care shouldn't be one-size-fits-all, and we hope this study sparks more personalized discussions between patients and their providers about pregnancy health.”
This research was funded by the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services, under a contract in support of the USPSTF, under AHRQ Contract Number 75Q80120D00006, Task Order Number 75Q80121F32009.
