So I made one of villagers a breeder to increase the population. I then dropped him next to Maiwa and watched them get ready to go indoors.
She walks into the hut with him following slowly. He is still walking towards the hut when she walks out and has a baby in her hands. He then walks into the hut and comes out alone.

I'd say Maiwa must be in her fertility prime... she just LOOKS at a man and gets pregnant!!!

I was trying to heal one villager and missed to a healthy individual. They embraced, but I stopped both of them from proceeding. She got pregnant without even going indoors.

I have found that when 2 villagers get together they do not have to go indoors to have the baby. If it is going to happen, it happens as soon as you put them next to each other. Next time you put 2 villagers together keep an eye on your population and you will see it go up by one if it is meant to happen.