The picture displayed on the room monitors at Texas Children's Hospital in Houston provides breathtaking detail. Beneath the watchful eye of a tiny camera surveying the inside of a uterus, an entire watery world slides into crystal-clear view. As the camera scans, an outstretched hand becomes visible, followed by an arm, then a mouth, and then the opposite hand. Tiny flecks of white spin across the monitor, skin cells awash in amniotic fluid.

   But the attention of Anthony Johnson, DO, is riveted elsewhere - on a network of blood vessels that merge and separate as they crisscross a single placenta shared by a set of identical twins. Working through a tiny incision, just .15 inches wide, Dr. Johnson uses a fetoscope - a telescope with a small camera attached to the end - as a surgical window into the pregnant woman's uterus.

   Looking through that porthole, he strives to decipher which blood vessels are connected and thus endangering the lives of the developing twin boys. "We're going to take out this one right here," he says. A green light glows on the monitor, highlighting the spot where he will direct the laser fiber that's threaded inside the fetoscope. A long beep sounds as he presses the foot pedal beneath the operating-room table. The laser fires, sealing off the errant blood vessel.

  Dr. Johnson and his surgical colleagues at Texas Children's are part of a small cadre of U.S. physicians who operate in the evolving and, some say, controversial field of medicine called maternal-fetal surgery. Contact for complete article.