Although you're presenting this as obviously absurd, taking that risk into account was long practice wasn't it? Forcing companies to pretend women are as likely to suddenly disappear for long periods as men is ultimately an economic choice and debatable as such in economic terms. It's essentially a kind of welfare that companies are made to pay, except instead of being an insurance scheme with actuarial rigor and smooth risk sharing over the entire population, it's a form of regressive taxation that disproportionately impacts smaller firms.

It can therefore be argued that it'd be better for society to take a different approach here, maybe more similar to (non-US) healthcare, e.g. mandatory maternity leave insurance, and then allow companies to simply price in the higher risk of extended absences. If they're no longer on the hook for paying wages this difference would be basically disruption risk and shouldn't be a particularly large difference for any but the tiniest firms, especially as motherhood comes with a much longer notice period than the typical resignation.