Hi alisarose,
Welcome to the forum. Yes, TLD, that sounds about right.
There is a very good book with all kinds of good basic information on reincarnation from early historical accounts to the present day, examining (and demolishing) most of the skeptic arguments, various controversies and the latest research by the likes of Dr Ian Stevenson. It's called 'Exploring Reincarnation' by Dr Hans Ten Dam (a Dutchman). He has done many regressions in the course of his Psychiatric practice, and obviously read a great deal of the literature that exists.
He says in general it is at about 3 months more or less - around about the time the mother starts to feel the 'quickening' when the baby starts to wriggle about. But it can also occur any time from conception to at birth - although these are the more unusual ends of the spectrum. People describe being attached to the mother by a silver thread and sort of 'hovering about' for some months until fully inhabiting the body close to birth.