Yevamot 37: Those Viable Babies

The babies who are born at 7 months or 9 months - with a paternity question. Why get into the 7-month baby possibility? That seems to be introducing complications for no good reason. But how much of this is determined by a majority of women? Depending on when they know they're pregnant... What are the real norms here? Also, a ln important discussion that begins with preventing mamzerim, and ends with not marrying someone you intend to divorce. Along the way, some rabbis put out the call for a (second) wife for just a day...