Here is another tip:
if your female pregnant sim owns a car, she can drive to work when she's supposed to stay at home. The carpool won't come and the game will tell you she's got maternity leave, but she can drive herself to work. She still gets paid either way but if there's a promotion in the midst, she can go and get it, I think it's handy too when it gives you a bit of a break from that sim being at home. If the baby is due to be born during that time, she'll just do it when she gets home.