Do Babies Dream in the Womb?

During the final phase of pregnancy babies spend about 90% of their time asleep, and when they sleep, nothing will wake them. One of the things revealed by the 4D scans is the fact that babies have REM, rapid eye movement sleep, a period of sleep where the eyes flick around behind the eyelids. 

Through ultrasound tests, researchers have seen evidence that babies in utero experience rapid eye movement (REM) sleep, which is associated with dreaming, at around 32 to 36 weeks. No one knows whether they're actually dreaming, since their brain waves can't yet be monitored, but doctors believe that it's certainly possible.

In fact, the sleep patterns of fetuses in this stage of development closely resemble those of newborns: They spend a lot of their time in REM sleep, but also in a quiet, deep sleep where there is no eye movement. Researchers have also observed babies in utero in a state of quiet alertness, which suggests they may be concentrating on something—listening to mom talking, perhaps.