At what gestational age do fetuses begin to exhibit active sleep behavior?

Fetuses begin to exhibit active sleep behavior around 36 weeks of gestation. During this stage, they engage in movements that are characteristic of REM sleep. These movements include twitching and irregular breathing patterns, which are essential for neurological development and reflect the developing brain’s activity. Active sleep is crucial for the fetus as it may contribute to the development of the central nervous system and may lay the groundwork for sleep patterns after birth. Prior to this gestational age, while the fetus may exhibit some reflexive movements, the distinct phases of active and quiet sleep do not manifest until around 36 weeks.