Pregnancy is not the natural outcome of sex.
Ask any couple visiting a fertility clinic and they'll explain that to you.
Pregnancy is not a punishment for having sex.
If pregnancy were punishment for bad behavior, it follows that children are likewise a punishment. That gets really theologically complicated really quickly. Especially if your religion calls god Father.
Pregnancy is risky. It's dangerous. It can destroy your body.
If pregnancy is not optional, it becomes criminal to ask anyone to get pregnant. It becomes forced labor on a battlefield.
(and I'm saying this as a mom of four who nearly died twice during pregnancies)
If your concern is unwanted pregnancies and saving the children:
- mandatory vasectomies for every penis out there (those are reversible)
- free birth control
- free healthcare for pregnant people
- free healthcare for all children
- a child stipend that starts with a positive pregnancy test
I really, REALLY, cannot understate how bad it would be if you were Christian and thought pregnancy was a punishment for sex while trying to believe that Mary was a virgin and pure and holy but that she also had a pregnancy before being legally wed.