if I were to tinkier, I wouldn't hamper sex drives, I'd arrange to have fertility decrease by half or more after every successful birth. Fuck all you want, but fewer mouths to feed. (and I understand that back in the day having a lot of kids was an economic advantage but not anymore)
In terms of number of pregnancies, is it really going to make that much of a difference if you have sex twice a week instead of four times?
No it does not. Most pregnancies occur among people who are trying to get pregnant. For the rest, fucking twice a week with a condom doesn't rather than four times with a condom does not reduce the chance of pregnancy significantly.