answer:If the 4 year old already was expecting a sibling, and the 4 year old was asking about the baby, I think I would have to say something. What’s her plan? To get pregnant again and hope her son just views it as a very long pregnancy? I’d just say the baby stopped growing, if her son knows the baby was inside her tummy. The baby stopped growing, and so it isn’t in her tummy anymore. Or, she could say mommy was wrong, and there wasn’t a baby, but she is hoping to get one. Make up whatever, but I think you have to address it with the son so it makes some sense to him. I’d also not tell my son I was preggers until about month 6.