that's a weirdly looking baby bump

i thought the same too! but a quick search shows that women can carry babies differently, and mc here was "carrying low" i.e. a bit lower on her stomach, compared to what we're used to which usually starts immediately under the boobs

Also, when labor/due date approaches, the belly can "drop" which is fitting since she suddenly went into early labor. Of course, people in this time didn't know much about delivery and things of that nature.