Why doesn't a premature baby sleep?

Premature babies' sleep patterns differ from full-term babies for several reasons:

• The nervous system is not mature. Premature babies' brain stem centers that regulate the sleep-wake cycle are not fully developed. That's why they have more REM (rapid eye movement) sleep and shorter deep sleep periods.

• Self-soothing ability is limited. The final trimester that's missing from birth is the period when a baby learns to filter responses to stimuli and develop the ability to fall asleep. Premature babies are more sensitive to external stimuli (sound, light, hunger, gas) and struggle to put themselves back to sleep.

• Feeding and blood sugar balance. They need to be fed more frequently—usually every 2-3 hours—which requires nighttime waking. Low blood sugar or insufficient calorie intake can also cause restlessness.

• Reflux and breathing sensitivity. Gastroesophageal reflux and apnea (breathing pauses) are more common in premature babies; these conditions cause fragmented sleep.

Current pediatric understanding is that sleep in premature babies only begins to become more regular around corrected age (not birth age, but age calculated from the last menstrual period) of 3-4 months. During this time, the most common clinical advice is for parents to keep expectations low, and increase external support such as swaddling and a dim environment.