Frequent use of certain herbal remedies in pregnancy may increase the risk of premature birth, a new study from Italy suggests.
In the study, women who regularly spread almond oil over their abdomens to prevent stretch marks in pregnancy were twice as likely to give birth before 37 weeks of pregnancy compared with women who did not use the herbal supplement.
The findings held even after the researchers took into account factors that might increase a woman's risk of giving birth prematurely, such as age, smoking and carrying twins.
However, more studies are needed to confirm the finding, the researchers said. The women in the study were not followed throughout their pregnancy, which could affect the results.
Concerns have been raised over herbal supplement use in pregnancy in the past, mainly because their safety for pregnant women is poorly studied. People may view herbal supplements as safe because they are "natural," but they contain ingredients that may cause adverse effects.
Because some herbal supplements can interact with certain medications, it's important for pregnant women to discuss any supplement use with their doctor, said Dr. Jennifer Wu, an obstetrician and gynecologist at Lenox Hill Hospital in New York City, who was not involved in the study.
A 2010 study found that about 9 percent of pregnant women in the U.S. used an herbal supplement, but that number was as high as 17 percent in some states. While use of almond oil among women in the study was high, Wu noted she has never had a patient who used this particular supplement. Italian women may be more likely to use herbal supplements during pregnancy than U.S. women, the researchers said.
The study involved 700 Italian women who were interviewed within three days of giving birth. The women were asked whether they used herbal supplements in pregnancy, and if so, which supplements and how often.
They found that 42 percent of women said they had taken an herbal supplement at least once in their pregnancy.
Additionally, 189 women (27 percent) said they were regular users of herbal supplements — meaning they used the supplements daily for at least three months during pregnancy.
Regular users were more likely to give birth to a child weighing less than 5.5 pounds compared with those who were not regular users, the study found.
Among regular users of any herbal supplement, about 15 percent gave birth before 37 weeks, compared with about 10 percent of those who were not regular users. The most commonly used supplement was almond oil.
Whether almond oil may actually prevent stretch marks has not been well-studied.
Future research is needed to determine how almond oil might increase the risk of premature birth. It could be that substances in the oil penetrate the skin and have adverse effects, the researchers said. For instance, some studies have linked supplementation with vitamin C and E — which are also present in sweet almond oil — and premature rupture of the amniotic sac (this is commonly referred to as "the water breaking").
The study, conducted by researchers at the University of Modena and Reggio Emilia, was published online Aug. 27 in the journal Human Reproduction.
Pass it on: Frequent use of almond oil in pregnancy is linked to an increased risk of premature birth.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.