Toward the other end of the process of childbearing, or gestation (Latin, gestare, "to bear," "to carry"), other researchers, quite independent of the sort of in vitro embryological work being done by Edwards, have been devising ways to save babies when a woman's natural machinery fails and the fetus is born too soon. This new branch of medicine is called "fetology." The fetus, its umbilical cord to the natural placenta haying been cut, is placed in an incubator which supplies heat and oxygen. There it is fed intravenously, and its breathing is forcibly assisted by an iron lung. By such means, doctors are now able to save most seven-month-old premature babies (average weight two pounds), some six- and-a-quarter- to seven-month-old "premies," and a very few under six and a quarter months. Incubators, which have been in use for a long time, substitute for many of the functions of the womb or placenta in order to permit the premature baby to gain size and weight. However, the baby is indeed a baby, and not a fetus anymore, because the umbilicus has been cut and the lungs are working. Some fetuses are expelled from the mother's body even earlier in gestation, and they die in an incubator.
The challenge is to build an environment that duplicates the ordinary environment of a fetus, in which it will not have to do things for which its body is unready. Fetologists are trying various approaches. Dr. Robert Goodlin at Stanford has put fetuses born less than six months after conception into a thick steel chamber where a saline solution saturated with oxygen is kept under a pressure of 200 pounds per square; inch, roughly the same experienced by a deep-sea diver at a depth of 450 feet. This immense pressure drives the oxygen through the skin of the fetus, sparing its lungs the need to work. But Goodlin has not solved the problem of buildup of carbon dioxide and other poisonous wastes, and no fetus has lasted more than forty-eight hours. Dr. Geoffrey Chamberlain, a British scientist then in Washington, D.C., on a year's research. scholarship, has kept alive some much younger fetuses, weighing only 300 to 980 grams, which were obtained during Cesarean section for therapeutic abortions.
Chamberlain's method is to save the umbilical cord and connect it to a combination heart-lung-kidney machine. In a report in the Ob-Gyn Observer on his most successful experiment, Dr. Chamberlain wrote, "A brisk spontaneous flow [of blood] was noted 22 minutes postpartum; the fetus was kept on the circuit for 5 hours and 8 minutes. Only when a cannula slipped out by accident and could not be reintroduced was the experiment halted." Earlier during gestation (when the organism is still actually an embryo), Dr. D. A. T. New of the Strangeways Laboratory in England has cut out from their mothers mice only 2 millimeters in length and cultured them on drops of blood plasma. and nutrient solution. The embryos have rudimentary hearts and nervous systems. During the time they continue to grow in Dr. News experiment, they quadruple in length, their hearts begin to beat, their brain, spinal cord, eyes, ears, guts, and kidneys develop, and their limbs begin to bud. However, as in Goodlin's experiments with human fetuses, the lack of a placenta or placenta-substitute to draw off poisonous wastes has been fatal to the mice within forty-eight hours.
Perhaps the most promising of all the approaches so far is that of Drs. Warren Zapol and Theodor Kolobow at the National Heart Institute, Bethesda, Maryland. Zapol and Kolobow separate a lamb fetus from its mother at a gestation age of 125 days. The complete gestation cycle in sheep is 147 days, so the equivalent human fetus would be seven and a half months, an age at which the ordinary incubator is pretty adequate. However, instead of incubating the premature lamb, causing its lungs to function, Zapol and Kolobow keep it alive by what they call "extracorporeal perfusion." This involves placing the fetus in an unpressurized bath of solution resembling amniotic fluid (the same stuff used by the Italian Petrucci in his "experiment"). The lamb's umbilical cord is attached by a catheter (segmented polyurethane Lycra, Du Pont Corporation) to a circuit of machinery including a pump, a bag of adult-sheep blood, a silicone membrane lung (Medical Division, Dow Corning Corporation), and a bottle of antibiotics and nutrients. As the fetus is removed from its mother, the system is attached and the lung and pump are put to work to take over.
The significant thing about this method is that it seems to achieve both nutrition and carrying-off of waste products. The levels of various chemicals in the lamb's body seem to stay fairly constant: in technical language, ". . . the fetus remains in a metabolically stable state lasting several days." Nor is death, after several days, caused by poisoning: "During perfusion, the fetus rested quietly in the artificial amniotic bath. About once each hour it moved its head...or legs spontaneously. It exhibited a strong sucking reflex as well as a withdrawal reflex when pinched. After 55 hours of perfusion, the fetus abruptly underwent cardiac arrest." Apparently Zapol and Kolobow have problems remaining to contend with. But perhaps these are not insuperable.
The editorialist of the New Scientist has said, ". . . the development of the 'perfect' artificial placenta can only be a matter of time."