It isn't the childcare itself, is the pregnancy and the 1st year that is the 'problem'. Women can and are as good entrepreneurs as men, but if for a second you think (exceptions excluded) women, during pregnancy and first months of a newborn can run a business without sacrificing something you must never been around that scenario. And if I was going to put a million dollars in your business and there is even a 5% chance you may end up pregnant, it will indeed be a minus in my book (as an investment though)
You either sacrifice the health of your baby with long nights, long working hours, stress, etc, or you sacrifice the company when you take those 2-3 days because morning sickness or tiredness don't allow you to be on your best.
Is it unfair? Yes, very, but pregnancy and breastfeeding is something that takes a toll on women and no matter what a partner tries to do to help, he can't really carry the baby in is belly or start producing milk. Think of it this way, if the entrepreneur was a man, it would be akin to asking how he would expect to keep focusing on their sports career (5+ hours practise a day) and running a VC-based startup.