Do employers not hire women because they expect that the women will get pregnant?

A friend of mine told me that employers discriminate against women when it comes to hiring since the employers expect that women will get pregnant and they don't want to have to pay for their time off. He says it happens this way in China at least (he is from China). So, does this happen in America? I have a hard time believing that this would happen since women are beneficiaries of affirmative action and since most HR managers are women.