This is such a bizarre and staunchly American attitude. In Canada you automatically get 17 weeks paid leave when having a child. You can also take an unpaid parental leave for up to 35 weeks and your employer cannot penalize you in any way for taking these leaves. The Canadian government is currently look at increasing the paid leave and applying it more equally to men and women in the future as the current system is felt to be inadequate.
Typically when someone goes on parental leave in my workplace a new employee is brought on temporarily under contract to "pick up the slack". If you choose not to have children or are not in a position to have children well then that's just too bad for you. Raising children is a huge commitment, both in time and money and there absolutely should be support from government and business to make major life events like this easier. It also encourages new mothers to do what's best for their health and the baby's by staying home and taking care of the newborn.
As someone from the outside looking in, the American system seems downright barbaric and more companies need to be doing what American Express is.