I can't believe you guys casual discuss about the pregnant woman without even go to the game to check. it doesn't that far anyway, you can just defeat the first monster then run straight to save the pregnant woman and see what are they talking.
The child at first seem normal (since both the woman and her brother doesn't know it's monster), the pregnant woman get caught by the zombie while she travel back to the village (there is a cart next to her) and we save her before she get eaten (as I said before, zombie only eat people, not bother to rape them).
When they get back, both the woman and brother not mentioned about she get raped by monster or anything. From the talk we can see that the church will take away any pregnant woman, said that their kid is monster and they'll cure them, but they never return, I don't read all the text in-game but assume the church become monster underling (like the Priest's case), they capture all pregnant woman to make them giving birth monster, so the woman in village kinda want to hide that they're pregnant.
After we cure the pregnant woman, she still pregnant, the baby not gone, so we can assume she's bearing a normal child after that.
So, I assume the monster somehow can infect any pregnant woman to turn their kid into monster (but they need go close to the pregnant woman first), that's why the monster randomly come out when villager give birth. For that reason whenever the villager see someone pregnant, they just suspect that woman "might" bearing a monster, not immediately confirm it, but they still scared, and they avoid to get pregnant (the reason the woman said she shouldn't try to bearing "his child"). The father can by anyone.
Also you can't apply normal logic (like why if Leila get rapped by the villager and end up pregnant monster child), Leila get a big stomach right after day she get rapped, it's absolutely not normal. The simply answer is the author not gonna go that much realistic develop his game.