The US, as a western country, are still lacking a good Parental / Maternity Leave program. Only the FMLA (Family Medical Leave Act), which was established in 1993, comes close to such a program. But still, the FMLA is not comparable to other Maternity Leave programs other countries are providing. The possible leave written down in the FMLA can be both used of men and women in the first five years of their baby. It is not essential for them to have the Parental / Maternity leave already during pregnancy or immediately after the child was born.
The leave can be individually taken for fifteen weeks. If the partners a choosing a combined leave, then this leave should not exceed 65 weeks. Thanks to the FMLA it is now also for men easier if they want to stay a home for a couple of weeks to support their wife with taking care of the baby. Especially in the first couple of month a combined leave is very useful for a family. Although the FMLA already supports men and women to stay at home with their child it is still a long way for the US to establish a good Parental / Maternity leave program which will be comparable to other countries. In the UK for example the employees insurance takes the responsibility of the monetary aspects of the maternity leave. In the UK the government offers a good Parental / Maternity leave program for workers.
When applying for maternity leave, it is not necessary for women to provide a medical certificate. They just have to submit a certificate that they are going to deliver a baby and they have to mention the approximate date of delivery of the child. The maternity leave can be used in different stages, means it is not required to avail the leave continuously.
There is definitely a need of good maternity leave programs. Therefore usually companies offer leave to their staffs, on humanitarian grounds, even if there is no law for paid maternity leave. The following links provide a good overview of the Parental / Maternity leave programs in the various countries: