1 Cor. 5:7
"Do not deprive each other, except by mutual agreement for a specified time, so that you may devote yourselves to prayer. Then resume your relationship, so that Satan may not tempt you because of your lack of self-control."
This temporary fasting, by consent, is the very way provided by God for husbands and wives to postpone or space their pregnancies, or even to avoid pregnancy entirely if there is a serious reason.
The Divine "design" is indeed Intelligent; and human couples, being intelligent, can have it down to a science.
Natural Family Planning Method As Effective As Contraceptive Pill, New Research Finds That's from Science Magazine, not a Catholic publication :o)
It proves the wisdom of practices recommended by Scripture: "There is a time to embrace, and a time to refrain from embracing." (Ecclesiastes 3:5)
God is a genius.
1 Corinthians 5:7 does NOT state that. You are reading way more into that verse than it says.