Some girls can control the development of babies.

Female red kangaroos give birth after just 33 days of gestation. Tiny and blind, the newborn must crawl through the fur of its mother’s abdomen to get to her pouch, where the baby can suckle and continue to develop. The female may become pregnant again almost immediately, but she can pause the development of the fetus until the joey in her pouch is further developed.

And sometimes boys give birth.