08/16/2012 11:16 am ET Updated Oct 16, 2012

Pregnancy Changes Mom's Gut Bacteria

belly of a young and fit...
belly of a young and fit...

Having a kid changes everything, from your sleep schedule to the status of that formerly spare room. The stable of bacteria that live in a woman's gut is also transformed when their host becomes pregnant. So finds research in the journal Cell. [Omry Koren et al., Host Remodeling of the Gut Microbiome and Metabolic Changes during Pregnancy]

The study looked at women in Finland. The women's microbial makeup changed dramatically between the first and third trimesters. The array of microbes in the gut went from looking normal in the first three months of a pregnancy to resembling what's found in patients suffering from metabolic disease in the last three.

But some of the symptoms of that condition--like weight-gain and slower sugar metabolism--can be beneficial to pregnant women, supporting energy storage that helps a fetus develop. Other symptoms, like inflammation, demonstrate that the immune system is functioning properly as a pregnancy comes to term.

Scientists don't yet fully understand what brings about the changes in gut bacteria--immune function is a suspect, but factors like hormonal signals aren't ruled out. The research suggests that other changes to the body, like puberty or old age, could also bring about microbial makeovers.