Baby's body clock begins to synchronize with local time while still in utero, study shows (opens in new tab)

Humans and most other organisms have internal biological clocks that track the daily cycle of sunrise and sunset. These clocks help time our sleep, metabolism and other essential body functions over the course of a day, creating daily patterns called circadian rhythms. Research shows that when these rhythms are disrupted—by jet lag, lack of sleep or irregular work schedules—people can suffer long-term negative health effects.