Baby in family tree but not on lot

No idea if this has happened to anyone else but I'm struggling to find answers.

One of my sims got a townie sim (his maid) pregnant. I kept inviting her round to the house to check on her pregnancy and then one time I invited her round, I realise she's no longer pregnant. I make her playable to check she's had the baby and she had; the baby is in her family tree and the relationship tab. I also check with my sim and the baby is in his family tree and relationship tab. 

I move my sim out to a different lot, invite her over and invite her to move in which she does. However, it's just her that moves in. No baby. Now I know the Sims 4 treats babies as objects instead of actual sims (????) so I check both their inventories and the household inventory. Nothing. It's really strange because the baby exists; I used the modifyrelationships cheat and it affected the relationship the mum has with the baby. It's as if the baby and bassinet have disappeared into the ether.

Does anyone know a solution for this?