A main source for the ages
Rolling over in infants: age, ethnicity, and cultural differences
E. Anthony S. Nelson, Ly‐Mee Yu, D Wong, H Y E Wong, Larina C.L. Yim · 2004 · Developmental Medicine & Child Neurology
- Children
- About 240 babies
- Where
- Hong Kong
- Ages
- Birth to 9 months
- How
- Mothers recorded on a chart when their baby first rolled
- What it found
- Babies first rolled from back to tummy at about 5 months on average, and from tummy to back at about 5½ to 6 months, the opposite order to what many textbooks say.
- Limits
- We have only read the summary. A third of the mothers who signed up didn't return the chart.