Wouldn’t it be nice if the female body would only allow conception based upon a conscious decision? No unwanted pregnancies, no “accidents” - every child would be planned and wanted.
If I were a Mad Scientist ... that would be my crime against humanity. Some genetic twist such that the default state was sterilization, and that only with a deliberate, conscious action; conception would be possible. Say, a large dose of Vitamin C (cheap, abundant, non-toxic) taken a few hours before conception.
I think you are a Mad Scientist even to conjure up such a weird scenario.