A 59-year-old woman gives birth to twins. A couple who lost two children to cystic fibrosis takes advantage of a new procedure that guarantees their next child will be free of the disease. A schoolteacher undergoes a new fertility treatment and gives birth to quadruplets. Are these people defying nature, or simply obeying one of its basic laws, when they enlist medical technology to aid the reproductive process? Is it fair to aid in the birth of children whose mothers may be ready for a nursing home by the time the children leave nursery school? Should medical insurance cover infertility treatments when millions of Americans have no health-care coverage at all? Should the government fund genetic research that might enable parents to choose the sex and the physical and mental characteristics of their unborn child?