I accidently discovered that too. I noticed once that as soon as my couple kissed, the population count went up by one. But I thought they still had to go to the hut. Then one day I accidently picked up the woman after they'd kissed and the count went up. When I put her down a baby appeared in her arms.

I don't know if this happens for everyone - success as soon as they kiss. But it sure saves time, especially when the father is elderly. Those poor men hardly ever make it to the hut before the woman comes out with the baby anyway.
