You might have heard some describe feeling particularly phenomenal while pregnant, euphoric even. Or, maybe, you yourself felt that way during your own pregnancy. A recent discovery by researchers at Harvard Medical School might help to explain why. Dr. Megan McCurry and colleagues have identified two gut microbes that could be responsible for that pregnancy glow. 

For most, the word microbe evokes fear. We often think of microbes as pathogenic bacteria that make us sick, but humans have billions of beneficial bacteria living on our skin, in our noses, and even in our guts, performing important tasks to keep us healthy. According to their new paper published in Cell, McCurry et al. identify two specific beneficial microbes responsible for producing massive amounts of a specific type of hormone, called progestins, during pregnancy –  roughly one hundred times more than in non-pregnant people. Progestin is thought of a sex hormone because of its known fluctuations during menstruation, but it’s also found in all human bodies and is responsible for various functions, including as a mood regulator. This could explain why some experience an improved mood during pregnancy. Interestingly, this team also discovered that the biological reaction responsible for producing progestins can only occur in the presence of hydrogen gas, which was found to be produced by other microbes living in the gut.

This discovery highlights that much of our physiology and experience of the world can be driven by the complex interactions between various microbes living within our bodies. Importantly, this work also contributes to the small, but ever-growing, pool of research on the biochemistry of pregnancy. Many questions are still left to be answered in this field, like: how do these microbes  increase in number in a pregnant person’s gut? When, if ever, do non-pregnant people experience increases in these particular microbes and the progestins they produce? And what are the consequences on mood in these cases? All together, cross-talk between busy bacteria might clue us into some of these remaining mysteries. 

This study was led by Megan McCurry with corresponding author Sloan Devlin at Harvard Medical School.

Corresponding Author: Nina C. Benites

Press article: Sex hormones in the gut soar during pregnancy — thanks to busy bacteria (Nature)

Research articleGut bacteria convert glucocorticoids into progestins in the presence of hydrogen gas (ScienceDirect)

Image credit: WikiMedia

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