When Do We Start Sleeping?

There have been a number of different theories on when sleeping and dreaming actually begins, with most scientists concluding that dreaming was not possible before infants actually started to become conscious and aware of the world around them. But in recent years, as we have gained the opportunity to see into the womb through ultrasound and other technologies, we have learned that sleep begins long before we are born, and that REM sleep is present in babies long before birth. The study of neonatal sleep is a relatively new science. We still are not sure when a developing fetus begins to alternate between being awake and being asleep, but we do know that babies that are born prematurely have a distinctive wakefulness pattern, and even though we know that a fetus is extremely active even when it is asleep, we still are able to discern that they spend between 16 and 20 hours sleeping.  It was in the mid-1950s, shortly after Rapid Eye Movement (REM) sleep was first discovered, that sleep scientists also discerned the fact that newborn infants experienced REM sleep. This came as a great surprise to those who had originally believed that the dreams that are a part of REM sleep required a level of awareness that newborns could not yet possess. But careful observation of sleeping two and three-month old children confirmed that the eyes were indeed moving in the characteristic REM pattern. Of course, it isn’t possible to confirm that they are actually dreaming since they are nonverbal, but there is copious information that points to the notion that even newborns experience images and dreams that use whatever exterior sensory input they have received to shape them. Early studies did not include a large amount of data on newborn brain wave activity, as many parents were hesitant about including their infants in scientific studies or experiments that involved having electrodes attached to their child’s heads, but enough did so that scientists were able to see the distinct differences in the children’s REM and non-REM sleep, as well as the remarkable amount of time that newborns spent in REM sleep as compared to adults. Their studies showed that babies born early but close to full term experienced REM sleep 60 to 80 percent of the time; compare that to adults, who spend only 25 percent of their sleep cycle in REM sleep. Also of interest while studying the sleep of premature infants and newborns was the fact that infants do have a built in circadian sleep cycle that is identical to their mother’s. This means that information or chemical signals are passed through the mother’s placenta to create the awareness of dark and light and the times when we are supposed to be asleep or alert, as actual light does not enter the womb to set the biological clock.  Interestingly, it is believed that the developing child also sends similar signals to the mother to let her know when they are ready to be born, and these signals nearly always occur in the evening. It is thought that this developed as a protective mechanism to ensure that babies would be born at night, when they were home and safe from predators.