Fetal surgery

New techniques have given surgeons a second chance

Operating on the fetus became technically feasible over 10 years ago,1 but it has remained semiexperimental; fetal surgery is attempted for strictly selected indications in a handful of centres worldwide. The slow progress of fetal surgery in the past decade and its poor survival record (19% for diaphragmatic hernia repair2) have led to assertions that it is a blind alley.

Yet many of the obstacles to success have been overcome. The technical aspects of operating on such fragile patients have been refined—paralleling the progress in postnatal surgery on very small and very premature infants. Postoperative uterine contractions, the most feared hazard of fetal surgery, can be better controlled by safe and effective drugs. Selection of patients has improved to reduce the chances of a fetus being needlessly exposed to antenatal intervention and its inherent risks. Finally, research has opened up alternative approaches to old problems. The question, therefore, is no longer whether fetal surgery will be a viable option; the question is when.

The main problem of antenatal surgery lay in the trauma of opening the uterus and exteriorising the fetus. Minimal access (laparoscopic) surgery has made a gentler approach to the amniotic cavity possible. Combining endoscopic innovations with the lessons from open fetal surgery has enabled a few centres to develop models of endoscopic fetal surgery that mimic open operations.3 The first applications of this new modality to human infants have succeeded in bridging a gap between the more limited techniques used by obstetricians and surgeons' operations outside the uterus. Endoscopic fetal surgery allows the surgeon to cut, to suture, and to ligate using techniques far less aggressive than those associated with hysterotomy.4 Fetal surgeons are not yet ready to perform endoscopic fetal laparotomies or thoracotomies: so far they have reported only umbilical cord ligation of parasitic, acardiac twins5 and the ablation of placental communications responsible for the twin-twin transfusion syndrome.6

Meanwhile, some of the early heroic fetal operations are becoming obsolete. This is shown by recent developments in the treatment of congenital diaphragmatic hernia. Until recently antenatal correction of this condition mirrored postnatal treatment: the surgeon restored the viscera into the abdomen and then closed the diaphragmatic defect. Two years ago, however, a known phenomenon was rediscovered, and used to correct the pulmonary hypoplasia that is the main cause of death in these infants. Obstructing the fetal trachea causes the lungs to grow in utero, and this leads to a gradual reduction of the viscera to the abdomen before the baby is born.7 The diaphragm may then be closed after birth. This exciting approach has already been used,8 and it may be further refined by the use of fetal tracheoscopy.9

Fetal surgery has wide potential for further development. The serendipitous finding that surgical incisions in fetal lambs heal without a scar has spawned an entire new field of research, complete with its own textbook.10 The immature (and therefore highly tolerant) immune system in the fetus allows transplantation of stem cells, which has been performed both experimentally and clinically.11

Fetal surgery is, then, very much alive, even if many obstacles remain. As the numbers of survivors increase the quality of life will need careful assessment. Will there be neurological sequelae?12 Do the lungs function normally after tracheal obstruction? Will the selection of patients for surgery ever be adequate, given the limitations of antenatal diagnosis? Will the indications for fetal surgery expand beyond life threatening conditions as the techniques improve and become less invasive? All these questions need to be answered before fetal surgery is allowed to become widespread. Hopefully, fetal surgeons will proceed in the future as cautiously as they have in the past.