'Unhealthy' Gut Microbes Benefit Pregnant Women

Research suggests that our bodies coevolved with microbiota that pregnant mom's actually use to support the fetus

The composition of microbes in the gut changes dramatically during pregnancy. Although these changes are associated with metabolic disease under most circumstances, they could be beneficial in pregnant women.

The study is published by Cell Press in the August 3rd issue of the journal Cell.

"This is the first in-depth characterization of the gut microbiota associated with pregnancy. The findings suggest that our bodies have coevolved with the microbiota and may actually be using them as a tool—to help alter the mother's metabolism to support the growth of the fetus." says senior study author Ruth Ley, Ph.D., Assistant Professor, Department of Molecular Biology and Genetics, Cornell University.

In nonpregnant animals,
changes to gut microbe composition
can cause symptoms of metabolic syndrome,
including weight gain,
abnormal glucose metabolism,
and inflammation—an immune response
that normally protects the body
but can cause health problems.

These symptoms also appear during pregnancy,
but the underlying causes have been unclear,
and few studies have examined the potential link
to gut microbiota during pregnancy.

To address this question, Ley and her team obtained stool samples from 91 pregnant women. They found that gut microbes changed in composition from the first trimester to the third trimester, becoming less "normal" and less diverse over time. Health-boosting bacteria decreased in abundance, while disease-related bacteria increased in number. In addition, signs of inflammation increased over the course of the pregnancy. "The changes in gut microbes were not related to diet, so we think the immune system or hormones play a role," Ley says.

When gut microbes from pregnant women were transferred to healthy germ-free mice, animals that received microbes from the third trimester became fatter and had higher levels of inflammation markers and worse glucose metabolism than mice that received microbes from the first trimester.

Koren et al.: "Remodeling of the gut microbiome and metabolic changes during pregnancy."

Original article: http://www.eurekalert.org/pub_releases/2012-08/cp-ci073012.php