An excerpt from an NIH faq on fellowship awards for grad students and postdocs.
I am planning on having a child during my fellowship. What are the NIH policies on family leave?
NRSA fellowship recipients are entitled to 15 days of sick leave per year, and up to 60 calendar days of parental leave if the institution provides that benefit to other fellows. The NRSA stipend will continue during those periods. Hence, the fellow would, in fact, be trading some research training time for the opportunity to stay at home with the child.