Over the years, multiple studies have shown that taking probiotics can have tremendous benefits for your digestive health—and your infant's too. But did you know that these good types of bacteria can also have positive effects on pregnancy?

A 2018 observational study published in the journal BMJ Open found that women who drank probiotic milk during pregnancy had lower risks of preeclampsia and premature birth—and the timing of when mamas-to-be drank the probiotics seemed to have significant bearing.

According to the findings, taking probiotics in pregnancy during the third trimester was strongly linked to a lower preeclampsia risk, while drinking probiotic milk in early pregnancy showed a decrease in preterm deliveries.

Preeclampsia is a serious medical condition marked by high blood pressure and protein in the urine that affects 2% to 8% of all pregnancies globally, according to the National Institute of Child Health and Human Development. And more than 1 in 10 babies are born premature, which is defined as arrival before 37 weeks of pregnancy, according to the World Health Organization.

"Modern obstetrics has not yet developed reliable methods to prevent or treat either of these conditions. Medical intervention in preeclampsia remains limited, although prophylactic aspirin treatment might be of importance. Interventions aimed at predicting and preventing spontaneous preterm delivery have also yielded limited success, although cervical length measurement and prophylactic progesterone treatment are promising," say the study authors.

To reach their findings, a team of Norwegian and Swedish scientists studied data on more than 70,000 pregnancies from the Norwegian Mother and Child Cohort Study (MoBa) launched by the Norwegian Institute of Public Health in 1999. As part of the countrywide study, mamas-to-be submitted their medical histories, as well as information on their health, diets and lifestyles at 15, 22 and 30 weeks of pregnancy.

The data analysis showed that more than one-third of pregnant women who participated in the MoBa study had consumed probiotic-rich milk during early pregnancy, while nearly a third took probiotics during late pregnancy. Close to a quarter of women drank probiotic milk before becoming pregnant.

The researchers compared information on probiotic milk consumption to incidence of pregnancy complications tracked by the MoBa study—which revealed probiotic use in late pregnancy lowered preeclampsia risk by 20% while taking probiotics during early pregnancy reduced preterm delivery risk by between 11 to 27%.

Because this is an observational study, which relied on women submitting their own health histories (meaning it could be subject to human error), more research in the form of randomized, controlled trials will need to be conducted on the benefits of taking food-based or supplemental probiotics in pregnancy to see if there are significant effects in preventing or minimizing pregnancy complications.

But, as the researchers note, it sure is a promising sign. Recent research has also shown that taking probiotic supplements in early pregnancy can help reduce morning sickness. Because probiotics are generally regarded as safe to take during pregnancy and breastfeeding, and without any apparent major downsides to drinking probiotics, you might as well stock up on some kefir at the store.