My baby is 6 month 21 days old still not able to hold her neck properly and can't sit without support..What to do ??

Sit without support will take time. But if the baby is active and taking feeds well don't worry. If concerned please meet your doctor

Try some tummy time ... Hope the growth and weight of the baby is fine.

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Priya few babies takes time, in your next visit to the paediatrician speak about this.