Do you think there would be even more people in the world if giving birth was pain free and the baby weight went away right after birth ?

Women who had very difficult births and/or complications might have more kids if they knew the next pregnancy would be easy breezy, but there are factors that play a far bigger role in deciding family size than fears about childbirth pain or weight gain. Money, for instance. Careers, life goals, and relationship stability to name a few more.

Bringing up kids is even more difficult rather than bearing and delivering.

The pain is like toothache. We don't forget the pain, but remember the joy of conception. Losing weight immediately, is a non-issue for many mums, who are more focused on the baby.

I don't think those are factors for most women. I wanted to be a mom, no matter what.

No. Because I know a few people who claim giving birth was not very painful. Plus I know women who were back to their before pregnant weight not long after giving birth.

You really think the pain of birth and weight is why people don't have more kids?

Twenty percent is an odd random guess.

Climate change would just kill them anyway.

I don't think that the pain and inconvenience of pregnancy are the main reason people avoid having any/more children, although I'm sure at least some people do. It's more about the pain and inconvenience of *children*. Pregnancy is a short term thing, parenting is a lifelong commitment of time, energy, and money.

No.  Very few people make their decisions about family size based on the size of their hips.

Probably so. AND if men had to give birth we wouldn't be having this conversation since we'd be extinct.