I'm 46 and my husband and I are actively ttc number 3. I have an 8 year old from a previous relationship and he and I share a 9 month old. He's turning 25 in two weeks and is excited to be trying for another child. We didn't want our shared child to grow up alone like my 8 year old has. Any tips as to how to help a baby gain weight while inside of the womb? My baby girl was in the 9th percentile when she was born. I'd like to try to avoid a repeat of possible.

TIA