But by the time they're ready for their next child, say at 39, those same medications are less likely to work.

http://www.babycenter.com/0_age-and-fertility-getting-pregnant-in-your-30s_1494695.bc

"I always tell women to think about that second pregnancy," says fertility specialist James Goldfarb, director of infertility services and IVF at the Cleveland Clinic Foundation in Cleveland, Ohio. "At age 35 or 36, many women need only minor, if any, medical intervention to get pregnant. But by the time they're ready for their next child, say at 39, those same medications are less likely to work."