> Female candidates are likely to get pregnant and society is better off with females getting pregnant because japan has a low birth-rate problem.

This is a value judgement, and a tedious one at that. You cannot compel women in a free society to have children to meet your expectations. If you want to encourage women to have children, you need to create an environment where it is equitable for them to do so without being unduly penalized.

Again: if your approach worked then Japan would not have a birthrate decline. This is, and has been, already their stance. Women are effectively removed from the workforce upon pregnancy. They are declining that proposition because it's unfair, and society COULD structure to redress that.