You've probably heard that if your baby is most active in the womb at night, he'll be a night owl once he's born. Some moms — as well as a few sleep experts — swear this old wives' tale is true, but no scientific evidence bears it out.
That doesn't contradict the fact that your baby is developing a sleep/wake cycle before he's born. At the beginning of your third trimester, he'll start having active or REM (rapid-eye-movement) sleep, the phase of sleep in which we dream. He'll add non-REM sleep — also known as quiet sleep — a month or so later.
Just like newborns, babies in utero don't have our typical day/night schedule; they rest for a few hours, and then are awake for a few hours. So don't worry about disturbing his sleep routine — you'll have to wait until a month or two after he's born for him to even have one!
Click here to learn more about the basics of good sleep, and see our ultimate guide to your baby's sleep to learn more about the nature of a baby's slumber.