Antioxidants tied to lower risk of preterm birth

Pregnant women who eat plenty of red- and orange-hued fruits and vegetables may have lower odds of giving birth prematurely, a new study suggests.

Researchers found that among more than 5,300 women who gave birth at one of four Canadian hospitals, those with higher blood levels of certain carotenoids were less likely to deliver preterm.

Carotenoids are pigments that give yellow, orange and red hues to a variety of fruits and vegetables, like tomatoes, carrots, red peppers, watermelon, oranges and orange juice. They also act as antioxidants—meaning they help protect body cells from damage that can lead to disease.

In the study, the one-half of mothers-to-be with the highest blood levels of certain carotenoids were 30 percent to 50 percent less likely to deliver prematurely than women with lower levels.

The protective nutrients included alpha- and beta-carotene, lycopene, and alpha- and beta-cryptoxanthin.

The findings, reported in the journal Epidemiology, do not prove cause-and-effect. There may be other things about women with high carotenoid levels that explain the association with lower preterm-birth risk, noted lead researcher Dr. Michael S. Kramer of McGill University and Montreal Children’s Hospital in Canada.

However, he told Reuters Health in an email, the findings do fit in with the recommendation to eat a well-balanced diet during pregnancy.

“Pregnant women are already being advised to eat lots of fruits and vegetables,” Kramer said, “so our results with respect to carotenoids should further encourage that healthy eating advice.”

The findings are based on blood samples from 207 women who gave birth preterm; each woman was compared with two others who delivered at term, at the same hospital.

Higher carotenoid levels remained linked to a lower risk of preterm delivery even after the researchers accounted for several factors that could help explain the connection—such as the mother’s smoking habits, weight, education and income.

If carotenoids do help prevent premature delivery, the reasons are not clear, according to Kramer. He speculated that it could be related to protection from any ill effects of environmental toxins, like air pollution, or exposure to bacteria or other infectious agents.

In contrast to the case with carotenoids, Kramer’s team found that high blood levels of another antioxidant—vitamin E—were linked to an increased risk of preterm birth.

Similarly, women with the highest blood levels of certain dietary fats, including unsaturated fats, showed a somewhat higher risk of preterm birth. Omega-3 fats, found largely in fish, were unrelated to preterm delivery.

The reasons for those connections are also unclear, and the findings could have been due to chance, the researchers note. Kramer said the results are too preliminary to make any recommendations.

SOURCE: Epidemiology, September 2009.