Is there a biological urge to have children in women?
The biological urge to find a mate means that an innate desire for children is unnecessary. Having sex with a partner pretty much guaranteed children before contraception was available. 

It's hard to imagine why an urge to have children would exist, but that's not the same as saying it doesn't -- but I also can't imagine how you'd be able to pull apart biological vs social pressures in such a complex and core part of being human.