For those who want children and can’t have them on their own, time is the enemy. But so is cancer. And money. And war. For those who fear an imperfect genetic history, it seems they must forge the steeliest of nerves in order to be successful. So many things can go wrong in the quest for a family, despite the high-tech world of fertility treatments and genetic counseling that hold promise for those who have been disappointed by old-fashioned measures.