After giving birth recently to a baby with cerebral palsy, a woman in Tarrant County, Tex., felt she had just cause to sue her obstetrician and hospital, claiming that he had caused the brain damage and paralysis by failing to perform a prompt Cesarean section despite ominous fetal heart tracings. Indeed, doctors are often found guilty of negligence in such cases, and together with their hospitals are ordered to pay enormous amounts in damages. But this doctor was lucky. He had saved a valuable piece of exonerating evidence that most other obstetricians routinely toss out-the baby's placenta.

Laboratory tests on the placenta found a high count of nucleated red blood cells, suggesting that some type of infection had been present. Given these findings, the hospital's lawyers argued successfully that the infection had caused the cerebral palsy two to three days before the baby was born, making the timing of the C-section irrelevant. "The placenta came in very handy," says Richard Griffith, the lawyer who represented the doctor. "I would love to see placentas in all cases involving problem deliveries."