I'm a man who has gone to bed early for quite awhile and I have never personally managed to get pregnant.

A good night's rest helps a lot of stuff you normally wouldn't associate with it. If you're actively trying to build muscle— you'll get nowhere without consistent, sufficient, sleep. Even all the way down to seemingly unrelated things like your general mood and your outlook on life are severely impacted by poor sleep. I wonder how many people, who have chronic "depression", got it from sleeping like shit for too many years in a row.

Well that certainly explains a lot (rolls over and sets alarm for Ob doctors visit in the morning)