During pregnancy, the placenta forms in the uterus, where it provides the fetus with nutrients and antibodies, and protects it from viruses and toxins. Then, it follows the baby from the body, still filled with a wealth of stem cells, collagens and cytokines that doctors and researchers have realized make it uniquely useful after birth, too.

Research has found placenta-derived grafts can reduce pain and inflammation, heal burns, prevent the formation of scar tissue and adhesions around surgical sites and even restore vision. They're also gaining popularity as a treatment for the widespread issue of chronic wounds.

And yet, of the roughly 3.5 million placentas delivered in the United States each year, most still wind up in biohazard disposal bags or hospital incinerators. That flummoxes Ms. Townsend, who returned to her job as a surgical assistant with a new perspective. "I'm constantly in these hospitals that don't donate or utilize the placental tissue," she said. "I hear the obstetrician say, I don't need to send that to pathology or anything; just trash it.' I cringe every time."

Because the placenta protects the fetus from the maternal immune system, its tissue is considered immunologically privileged: Even though it's technically foreign tissue, placental grafts have been found not to prompt an immune response in transplant recipients. That means, unlike skin grafts from animals or cadavers, placental grafts are basically not rejectable. The placenta's tissue also contains proteins and sugars that spur patients' cells to multiply quickly, and the grafts have been shown to encourage rapid skin and tissue regrowth. In one case, doctors essentially regrew the tip of someone's nose.

"We call it a healing factor, but a better way to put it is it's a regenerative factor," said Dr. Scheffer Chuei-Goong Tseng, an ophthalmologist in Miami who's spent decades studying the use of placental grafts to treat eye injuries and diseases and whose company manufactures and sells them. "Healing is broad; you can heal but still scar. We are talking about healing almost without scarring."