The scientific way our bodies prepare for motherhood during pregnancy

Everyone knows that new moms get very little sleep. Between constant feeding sessions, dealing with the euphoria and anxious energies and non-stop diaper changes of early parenthood, newbie mothers definitely experience a sleep deficit.

But new research from Washington University in St. Louis says that lack of sleep actually starts before the infant arrives because pregnant moms start waking up earlier. According to the study, the daily schedule in pregnant women and mice shifts a few hours forward during the first trimester. Perhaps our bodies are preparing us for what is to come.

"What happens in early pregnancy is that they shift their total activity to earlier in the day," says Erik Herzog, professor of biology in Arts & Sciences and lead author of the new study. "But they don't seem to sleep more or be more active during their early pregnancy. It's just a change in their daily timing."

The new changes in the timing may put a pregnancy at risk, as sleep-wake schedules have been associated with preterm birth and other poor reproductive outcomes. On a national level, one in 10 babies is born before 37 weeks of pregnancy have been completed. And according to the study, this can happen because of disruptions of regular sleep-wake schedules. During this time, activity levels also dip, but during the later stages of pregnancy, the daily schedule stabilizes.

"This finding is fascinating because while we know that miscarriage, preterm birth and other serious complications during pregnancy are linked to disruptions in a mom's circadian rhythm, we don't know how it works," said Kelle H. Moley, MD, chief scientific officer for March of Dimes in a statement. "This study takes us one step closer to understanding how normal circadian rhythm supports healthy pregnancy."

Researchers from the same study also observed that the amount of activity during pregnancy was significantly reduced—in both women and mice.

Ironically, sleep in medicine is poorly studied, says Emily S. Jungheim, MD, associate professor in the department of obstetrics and gynecology in the School of Medicine and a co-author on the new study. "Even among healthy women and men—those who eat well, who exercise—the one thing they're willing to do without a second thought is skimp on their sleep. A lot of people don't pay attention to how important it might be."

The good news is, though it doesn't seem like it, a lack of sleep can always be corrected. And ultimately, if you're looking to have a healthy baby, putting sleep at the forefront of your daily routine is a great step in the right direction.

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