My little one is 6 months old, but isn’t showing any sign of rolling over. However, he is sitting up on his own. I know all babies learn things at different rates, but I want to know if I should be worried if he doesn’t roll over?
Nelson, E. A., Yu, L. , Wong, D. , Wong, H. and Yim, L. (2004), Rolling over in infants: age, ethnicity, and cultural differences. Developmental Medicine & Child Neurology, 46: 706-709. doi:10.1111/j.1469-8749.2004.tb00985.x
This is the page and here's the pdf view.
‘Roll over’ in the Denver Developmental Screening Test (Frankenburg et al. 1981, 1992) means that the child is seen to roll from back-to-stomach or from stomach-to-back, or the parents have seen the infant roll completely over from back-to-stomach or from stomach-to-back at least twice.
In table 3 on page 708, they compared the mean ages of when infants learned to roll over from different studies. This study showed that
- 25% of the 4.2 month old
- 50% of the 5.0 month old
- 75% of the 5.7 month old
- 90% of the 6.6 month old
infants had already learned to roll over. But the studies show some variety, e. g. take the Shanghai study with quite some delay.
Taking the arithmetic means of all the studies together, I got
- 25% of the 3.5 month old
- 50% of the 4.5 month old
- 75% of the 5.1 month old
- 90% of the 6.0 month old
infants having learned to roll over. It seems that yours would be a little late.
The CDC Milestone Moments (pdf download) notes that 4-month-olds may be able to roll over from back to tummy. They expect 6-month-olds to be able to roll over and, if not,
Tell your child’s doctor or nurse if you notice any of these signs of possible developmental delay for this age, and talk with someone in your community who is familiar with services for young children in your area, such as your state’s public early intervention program.
I suggest to follow the advice of the CDC - better safe than sorry - and talk to your doctor to see if there's anything wrong with your child.