Firstly, I suggest writing either $100M or $100 million.
Your sentence sounds better to me with '52 parents' as its subject. That requires the currently passive voice of the verb 'to raise' to be changed to the active voice.
Ask who/what/... does the action of the verb 'to raise'. Answer, the parents. Not always, but you should usually make your answer to that question the subject of your sentences. That gives you
52 parents have raised $100M for their ...
Baby's is wrong. That means one baby with 52 parents.
Possessive forms of plural words ending with 's' require the apostrophe is placed after the 's'.
52 parents have raised $100M for their babies' treatment of extremely
It then sounds better to me if treatment of is moved earlier.
52 parents have raised $100M for the treatment of their babies' extremely