Babies really do grow while they sleep

These logs were kept for between four and 17 months. The researchers measured the babies regularly and then compared their length and weights with the findings from the sleep diaries.

The results showed that when babies started taking more naps or slept more overall, they were likely to have a growth spurt. Babies were 43% more likely to have a growth spurt for every extra nap they took and every hour of extra sleep increased their likelihood of a spurt by 20%.

“Little is known about the biology of growth spurts,” explained the study’s author, Professor Michelle Lampl. “Sleep irregularities can be distressing to parents but these findings give babies a voice that helps parents understand them and show that seemingly erratic sleep behavior is a normal part of development.”

Babies didn’t just grow longer while they slept, they also put on weight, especially gaining fat around the tummy. Though researcher aren’t sure exactly why this happens, they have suggested the growth could be down to the different hormonal signals at work while babies sleep, that makes their bodies work differently.

Find out more to help your newborn get enough sleep, how to keep the nursery a safe temperature for nap time and getting the perfect sleep routine for both of you.