My wife's not a ppruner but I'll try to paraphrase her thoughts on the matter, she is a professional pilot and was just starting her first airline command at the time she fell pregnant.
She had every intention of getting back into the flying post pregnancy, but to be honest once we actually had the baby, her feelings changed, we just weren't prepared to make those sacrifices. Two kids now and the second one's just starting school, she'll get back into flying in some capacity in the near future but it won't be airline because we both agree that we just don't want both parents being away from home for multiple days at a time and working antisocial hours, like Daddy does.
The unfortunate biological fact is, that it's always the woman who loses her pilot medical certification for several months, when it's time to start a family. And this industry is so brutally hard for anyone, man or woman, once they've been out of it for a while, to get back into it. And it's very unforgiving of part time employment or 9-to-5 options or all the good things you can normally get in office jobs.