Researchers studied over 23,000 pregnancies to see if a natural nutrient called myo-inositol could help prevent heart defects in babies. They found that pregnant women who consumed more myo-inositol—either through supplements or food—had lower chances of having babies with certain types of heart defects. The study looked at women’s nutrient intake during the three months before pregnancy through the third month of pregnancy, which is a critical time for baby’s heart development. While these results are encouraging, experts say more research is needed before making strong recommendations.

The Quick Take

  • What they studied: Whether pregnant women who consumed more of a natural nutrient called myo-inositol had lower chances of having babies born with heart defects.
  • Who participated: Over 23,000 pregnant women in the United States—about 11,750 who had babies with heart defects and 11,415 who had healthy babies without birth defects.
  • Key finding: Women who took myo-inositol supplements had about 21% lower odds of having a baby with heart defects. Women with the highest total intake (500+ mg per day from all sources) had 12-15% lower odds of certain types of heart defects.
  • What it means for you: If you’re planning to become pregnant, getting enough myo-inositol may help reduce your baby’s risk of heart defects. However, talk to your doctor before starting any supplements, as this is one study and more research is needed to confirm these findings.

The Research Details

Researchers used a case-control study design, which means they compared two groups of women: those who had babies with heart defects and those who had healthy babies. They looked backward at what these women ate and what supplements they took during the critical early pregnancy period—three months before getting pregnant through the third month of pregnancy. This timing matters because a baby’s heart forms during these early weeks.

The researchers asked women detailed questions about their diet using a food frequency questionnaire, which is like a checklist of common foods and supplements. They specifically looked for myo-inositol from both supplements and natural food sources. They then used statistical methods to compare the two groups and figure out if higher myo-inositol intake was connected to lower heart defect risk.

This study used data from the National Birth Defects Prevention Study, a large U.S. database that tracks birth defects and pregnancy information. Using existing data like this is efficient and allows researchers to study large numbers of people.

The case-control design is particularly useful for studying rare conditions like heart defects because researchers can specifically recruit women who had affected pregnancies. This approach is more practical than waiting years for heart defects to occur in a large group. By looking at what women consumed before and during early pregnancy, researchers can identify nutrients that might protect developing babies during the critical heart-formation period.

This study has several strengths: it included a very large number of participants (over 23,000), used a well-established national database, and adjusted for other factors that might affect heart defect risk. However, the study relied on women remembering what they ate months or years earlier, which can be inaccurate. The study also couldn’t prove that myo-inositol directly caused the lower risk—only that it was associated with it. Additionally, women who take supplements may have other healthy habits that also protect their babies.

What the Results Show

Women who took any myo-inositol supplements had about 21% lower odds of having a baby with heart defects compared to women who didn’t take supplements. This was a meaningful reduction. When researchers looked at women with the highest total myo-inositol intake (500 mg or more per day from all sources combined), they found 12% lower odds of heart defects overall.

The protective effect was strongest for certain types of heart defects. For example, women with high myo-inositol intake had 39% lower odds of septal defects (holes in the heart walls) when looking at supplement use alone. For total intake, the reductions ranged from 9% to 15% depending on the specific type of heart defect.

The study found benefits for several different types of heart defects, including conotruncal defects, left ventricular outflow tract defects, right ventricular outflow tract defects, and atrial septal defects. This suggests the nutrient may have a broad protective effect rather than helping with just one type of defect.

The researchers found that the protective effect appeared consistent across different types of heart defects studied, suggesting myo-inositol may work through a general mechanism that supports heart development. The benefits were seen both when looking at supplement use alone and when combining supplements with dietary sources. This consistency strengthens the findings somewhat, though it doesn’t prove causation.

This is one of the first large studies to specifically examine myo-inositol and heart defects in babies. Previous research has shown that myo-inositol plays a role in cell development and may help with other pregnancy-related conditions like gestational diabetes. This study extends that research by suggesting the nutrient may also protect against heart defects, though the mechanism isn’t yet fully understood.

The main limitation is that women reported their diet from memory, which can be inaccurate. Women who take supplements may also eat healthier overall or have other healthy habits that protect their babies, so we can’t be sure myo-inositol alone caused the benefit. The study also couldn’t determine the ideal amount of myo-inositol or the best time to start taking it. Additionally, the study included mostly white women, so results may not apply equally to all populations. Finally, this is an observational study, not a randomized controlled trial, so it shows association but not definitive cause-and-effect.

The Bottom Line

If you’re planning to become pregnant, discuss myo-inositol with your doctor. While this study suggests it may help reduce heart defect risk, it’s not yet strong enough evidence to recommend it universally to all pregnant women. Your doctor can help determine if it’s appropriate for you based on your individual health. Myo-inositol is found naturally in foods like beans, grains, and nuts, so eating a balanced diet is a good start. If you’re considering supplements, talk to your healthcare provider first, as they can advise on appropriate dosing and whether it’s right for you.

This research is most relevant to women planning pregnancy or in early pregnancy. It may be especially interesting to women with a family history of heart defects or those with conditions like polycystic ovary syndrome (PCOS), where myo-inositol is already being studied. However, this study doesn’t mean all women need to take myo-inositol supplements—more research is needed before making that recommendation. Women should discuss this with their healthcare provider rather than self-treating.

Heart defects form during the first three months of pregnancy, so the critical window for myo-inositol intake appears to be from three months before pregnancy through the third month of pregnancy. If myo-inositol does help prevent defects, the benefit would likely be seen at birth when the baby’s heart structure is fully formed. You wouldn’t see immediate effects during pregnancy.

Want to Apply This Research?

  • If planning pregnancy, track daily myo-inositol intake from both supplements and food sources (in mg per day). Set a goal of 500+ mg daily during the periconceptional period and log intake through the first trimester.
  • Add myo-inositol-rich foods to your diet: include beans, whole grains, nuts, seeds, and leafy greens in daily meals. If supplementing, work with your healthcare provider to determine appropriate dosing and set reminders to take supplements consistently during the critical early pregnancy period.
  • Track weekly average myo-inositol intake and monitor consistency of supplement use if recommended by your doctor. Note any dietary changes and maintain records to discuss with your healthcare provider at prenatal visits.

This research suggests an association between myo-inositol intake and reduced heart defect risk, but it does not prove that myo-inositol prevents heart defects. This study should not be used as a reason to start or stop any medications or supplements without consulting your healthcare provider. If you are pregnant or planning to become pregnant, discuss all dietary supplements with your doctor before use. Heart defects have multiple causes, and this nutrient is just one factor being studied. Always follow your healthcare provider’s recommendations for prenatal care and supplementation.