A study out today by the American Society for Nutrition found that iron deficiency in pregnancy is more common than previously thought—even among people who take prenatal vitamins.

The observational study, published in The American Journal of Clinical Nutrition¹, collected blood samples from 641 generally healthy pregnant people in Ireland at 15, 20, and 33 weeks of pregnancy. They also gathered information from the participants about their pregnancy, delivery, and baby 72 hours after delivery. The study found that while none of them were anemic in the first trimester, more than 80 percent of them were considered iron-deficient by the third trimester.

Notably, three-quarters of the participants took a supplement with iron in pre/early pregnancy. The authors note that taking iron supplements did seem to improve iron levels throughout pregnancy somewhat, but levels were still low in the third trimester for most people.

These findings suggest that even with supplementation, the iron needs of pregnant people are significantly high and often unmet—leading to potential health complications for parents and fetuses.

This study comes on the heels of another, published earlier this week in JAMA², which found that nearly 1 in 3 American adults may have undiagnosed iron deficiency. The analysis included data from more than 8,000 people, which revealed that 14 percent had low blood levels of iron while another 15 percent had the right blood levels but their bodies couldn’t use the iron properly (something called functional iron deficiency).

It’s maybe no surprise, then, that the research published today found that about half of people enter pregnancy with already-depleted iron levels.

So, can taking iron pills help improve your iron stores before and during pregnancy? Here, we spoke with an OB/GYN to learn more about the risks of iron deficiency in pregnancy and how to avoid it.

Iron deficiency in pregnancy is common (but it can still cause issues)

“About 20 to 30 percent of women are anemic during their third trimester,” says Sherry Ross, MD, an OB/GYN, author, and co-founder of Oneself and the Women’s Health and Wellness School on the Mproov app. This is likely because iron needs increase tenfold when you are pregnant, according to The American Journal of Clinical Nutrition study. Meeting your growing iron needs—especially if you had low levels prior to pregnancy—can be difficult.

“During pregnancy, the body’s blood volume increases significantly, allowing red blood cells to help support a growing baby and placenta,” Dr. Ross says. “Iron helps make hemoglobin in red blood cells, which provides oxygen to the baby.” Without enough hemoglobin, your body can become anemic.

Common symptoms of anemia include extreme fatigue, weakness, chest pain, irregular heartbeat, and cold hands and feet, per the Mayo Clinic. But in pregnancy, it’s associated with a higher risk of complications like postpartum depression, postpartum hemorrhage, preterm birth, low birth weight, and babies that are small for their gestational age. Even without anemia, low iron in pregnancy can result in certain long-term developmental challenges for children, per the study.

This is why it’s so important to regularly check in with your OB/GYN or healthcare providers about where your iron levels are at and what supplementation should look like for you—especially if you’re already anemic before pregnancy. (More on this below.)

We need more routine and thorough iron testing

Iron deficiency is more common in women, per the JAMA study, but unfortunately, its signs and symptoms can be written off as other things by healthcare providers—such as chronic fatigue or anxiety. But because iron deficiency can lead to negative health outcomes (whether pregnant or not), it’s important to make sure you’re getting your levels checked regularly.

“It is recommended to check iron levels during the initial pregnancy intake visit in the first trimester, and again when gestational diabetes testing occurs between weeks 26 to 28 weeks of pregnancy,” says Dr. Ross. But “your iron levels should be checked more often if you’re anemic during pregnancy.”

But according to the study authors, this screening practice is not universally routine. While the International Federation of Gynecology and Obstetrics recommends all pregnant people get screened in their first trimester (and all women of reproductive age, for that matter), the U.S. Preventive Services Task Force says there’s not enough evidence to regularly screen for iron-deficiency anemia in pregnancy.

There’s also not a generally agreed upon diagnostic criteria for iron deficiency during pregnancy, per the study. This could mean that what’s considered a “healthy range” for non-pregnant women could actually be a deficiency for some pregnant people.

Ultimately, the study authors call upon the American College of Obstetricians and Gynecologists (and the U.S Preventive Services Task Force) to change their approach to diagnosis—by screening all pregnant people for iron deficiency regardless of whether they have anemia, and to recommend supplementation “for the most frequent nutrient deficiency disorder that we encounter.”

How to make iron supplements more effective

Along with regularly checking your levels, iron supplements are still the best way to prevent deficiency in pregnancy. “Taking iron supplements, in addition to a prenatal vitamin, helps maintain iron levels before becoming too anemic,” says Dr. Ross.

In general, it’s recommended pregnant people get about 27 milligrams of iron per day, according to Yale Medicine. But it’s worth noting that sometimes iron pills are hard to swallow (literally, they’re huge) and they can come with side effects, like nausea or constipation.

Here are Dr. Ross’ top tips for making iron pills most effective, especially if you’re already anemic or get those uncomfortable side effects:

• Ask your doctor about the best type and dosage: Talk to your doctor about the best forms of iron to take while pregnant. The amount and kind you take may depend on your level of anemia. Dr. Ross notes that ferrous bisglycinate and ferrous sulfate are two easily absorbable forms of iron that tend to be gentle on the stomach.
• Look for supplements with vitamin C: Vitamin C helps with iron absorption.
• Consider supplements with a stool softener: Constipation is a common side effect of iron supplements, which is why some prenatal supplements contain a stool softener, Dr. Ross says. Stool softeners are generally considered safe during pregnancy, but ask your doc first if this is right for you.
• Take them on an empty stomach: If you can, try taking iron pills on an empty stomach, either one hour before eating or two hours after eating, for maximum absorption.
• Avoid foods that interfere with iron absorption: This includes calcium-rich foods, dairy products, and drinks like coffee and tea. Try not to have these around the same time you’re taking your iron supplement (but you don’t need to cut them out completely).

—reviewed by Andrea Braden, MD, OB/GYN