More and more women are waiting longer to start a family thanks to widely available family planning and changing social norms. These days at least one in twelve women has their first child after the age of 35. As natural fertility declines through a woman's thirties and forties, many are turning to in vitro fertilization, or IVF. In the last decade, the number of women over forty who used IVF jumped more than 41 percent. With news of women giving birth after sixty, fertility seems almost indefinite. But IVF and other reproductive technologies cannot extend a woman's baby-bearing abilities forever. Even the success of assisted reproduction drops off dramatically after forty. So says a report in the journal "Fertility and Sterility." Many much older mothers have become pregnant with donated eggs rather than their own. The study notes that one solution for women who wish to delay pregnancy is to freeze their own eggs years ahead of time. But when family planning for the long term, it might be wise to realize that even the stork eventually gets too old to fly.