In the study, the researchers looked at data collected from about 70,000 pregnant women in Norway, who were participants in the long-running Norwegian Mother and Child Cohort Study. As a part of that study, the women completed questionnaires about their health history and lifestyle habits at the 15th and 30th week of pregnancy and provided information about their diets at the 22nd week of pregnancy.
The lifestyle questionnaires asked women about their intake of probiotic milk products before pregnancy, as well as during early and late pregnancy.
About 23 percent of the women in the study reported that they drank probiotic milk before becoming pregnant, about 38 percent drank it during early pregnancy, and 32 percent consumed probiotic milk during late pregnancy. The women drank about 1.5 cups a day, on average, of milk products containing the live active bacteria. The results appear to suggest that consuming probiotics late in pregnancy can lower the risk of preeclampsia by reducing symptoms, such as high blood pressure and protein in the urine, which tend to occur in the third trimester.
Both of these conditions are associated with a higher degree of inflammation in the body than can be expected in a healthy pregnancy. Probiotics or "good" bacteria might help reduce inflammation in the body and, therefore, potentially reduce the risk of these pregnancy complications, Nordqvist told Live Science.
The timing of probiotic-milk intake was interesting as it appeared to make a difference for premature delivery: Drinking probiotic milk in early pregnancy was linked to a 21 percent lower risk of preterm delivery, compared with not drinking probiotic milk during early pregnancy. One explanation for this result is that preterm delivery can often be related to infection, which leads to inflammation in the body. The results suggest that if the body's inflammatory response is lowered at an early stage of pregnancy, this might reduce the risk of giving birth too early.
The researchers, however, noted that the study had limitations. For example, the researchers weren't able to evaluate which of the probiotic milk products or which strains of bacteria in them may have inflammation-lowering effects. Also, the study did not prove cause-and-effect; instead, it showed an association between probiotic milk and these pregnancy complications. It is a step in the right direction, but more research is needed before doctors can make recommendations that pregnant women drink probiotic milk to help prevent complications.