Many Americans look forward every year to that fall weekend when they can turn the clock back and regain the hour of sleep they lost in the spring. (Public service announcement: This year Daylight Savings Time ends Nov. 6 in the United States).
And if you have young children, you might love the prospect of getting that extra hour of sleep, but, sadly, you probably won’t get to enjoy it because their body clocks still think it’s daylight savings time.
About a quarter of the world’s population change their clocks in the spring and the fall. It’s such a common experience that scientists have wondered how it might impact health.
Studies have investigated whether the one hour lost or gained could be linked to a spike in heart attacks or car crashes, although that doesn’t appear to be the case. But what about if you’re pregnant? Could springing forward or falling back increase your chance of going into labor?
It’s plausible, according to a new study published by Swedish and Norwegian researchers in the journal BMJ Open. Some scientific evidence suggests that stress hormones play a role in triggering labor, and sleep deprivation and disruption in your clock might elevate levels of those stress hormones.
One small previous study, published in 2014 by Harvard scientists, suggested sleep deprivation might trigger preterm labor. The researchers interviewed women who had delivered a baby preterm and, for comparison purposes, women at a prenatal checkup who were just as far along in their pregnancy but hadn’t yet delivered.
They found that the women who had delivered a baby preterm were 4 ½ times more likely to have not slept well before they went into labor than the pregnant women in the 24 hours before their checkup. (In case you’re interested, the study also linked skipped meals, sexual activity and spicy food to preterm labor, but the scientists called for larger studies to evaluate modifiable risk factors related to preterm birth.)
The new study–whose authors say is the first to examine the effect of changing the clock on the onset of labor–used data about spontaneous deliveries (neither induced vaginal deliveries nor elective C-sections) from 1993-2006 from the Swedish Medical Birth Register, which includes pretty much every baby born in that country. The scientists compared the number of spontaneous deliveries in the week after the spring and fall time changes with the number in the week before the time changes and the second week after them.
Turns out they didn’t find much difference in the number of deliveries or in the number of preterm deliveries in the time periods studied. They didn’t have information about the new mothers’ sleep quality, but they note that some women in their study might already have been on parental leave when the time change occurred, so they might have been less affected by the shift than working women.
Plus, they said, their findings might not be generalizable to people living at different latitudes, a factor that contributes to the number of hours of daylight. For example, the authors wrote, earlier studies about the effect of changing the clock on heart attacks suggest it’s milder in Sweden than in countries at lower latitudes.
The bottom line is that extra hour you get when you fall back probably won’t increase the chance that you’ll go into labor, but you might want to make sure you’re well-rested as your due date approaches.