Just another FYI. When I drop a male villager on a nursing mom to get her to wait for someone, I've found it doesn't always happen on the first try. Sometimes it takes days, but the clock eventually did start. There was one nursing mom that no matter how many times I dropped a male villager on her, nothing happened. I granted her youth a couple of times, but I eventually let her pass away. When she did pass away, the baby was born.