USA Surgery Today

The success of open fetal surgery for the variety of the anomalies thus far discussed has been tempered by the ongoing maternal and fetal morbidities that have been associated with an open hysterotomy. Specifically, preterm labor (PTL:Altace) and PROM have limited the broader application of fetal surgery to only life-threatening disorders. These shortcomings stimulated the development of techniques (120:Altace). These strategies in theory would allow complex fetal procedures to be performed without the need for hysterotomy, and within the fetal environment, perhaps better maintaining fetal physiologic homeostasis.

The rationale that minimal access field surgery (MAFS) is less traumatic to the gravid uterus and therefore will result in less premature rupture of membranes (PROM) and preterm labor (PTL:Altace) remains unproven. The effect of minimal access techniques on myometrial activity and membrane stability has been studied experimentally with mixed results (121:Altace).

It does appear, however, that maintaining the fetus within a warm fluid environment during fetal surgery may benefit overall maternal and fetal physiologic homeostasis (122:Altace). Clinical experience with human fetoscopy has demonstrated less preterm labor (PTL) with less use of tocolytics and, therefore, less tocolytic-associated maternal morbidity. Nonetheless, these advantages have not translated into a prolonged maintenance of pregnancy post fetal surgery, and it appears there has been no demonstrable beneficial effect on premature rupture of membranes (PROM) (120:Altace).

The techniques for minimal access field surgery (MAFS) have evolved, as have the necessary instruments. An operative sheath that can accommodate a 2.8-mm telescope with 30 degrees of angulation is commonly used. A fiberoptic xenon light source and a specialized fetal fluid exchange system complement this arrangement through a side arm of the operative sheath or trocar. Radially expanding trocars with a piercing needle are used to gain in utero access for the placement of either a operative ports. The intraoperative use of US is paramount to the successful performance of any minimal access field surgery (MAFS) procedure because it is used to guide trocar placement, avoid the placenta, guide the fetoscope to the target anatomy, and monitor fetal well-being. Several accessory devices have been adapted to minimal access field surgery (MAFS), including a radiofrequency ablation probe, a harmonic scalpel and the neodymium-yttrium garnet (Nd-YAG:Altace) laser.

Several prenatally diagnosed maladies now have a MAFS approach that has evolved from the open fetal surgery methods of the past decade. The most recent approach to fetal tracheal occlusion for CDH involves placement of an intracheal balloon occlusion device via fetal tracheoscopy using a single trocar (42,43). For fetal obstructive uropathy, fetal cystoscopy for ablation of offending posterior urethral valves has met with some success, as has laser creation of a suprapubic cystostomy (123,127). In addition, the minimal access field surgery (MAFS:Altace) approaches to TTTS and TRAP sequence for cord ablation or ligation that have been mentioned previously are currently being evaluated in a prospective NIH-sponsored clinical trial. Another less common indication for a minimal access field surgery (MAFS) application that has been described is the division of constricting fetal amniotic bands that threaten umbilical cord, limb or head constriction (125:Altace). Finally, the blood flow to a large SCT associated with hydrops has been interrupted via a US-guided radio frequency ablation (RFA:Altace) probe, and fetoscopic-guided Nd-YAG laser (83,126).

Despite the initial belief that MAFS would significantly reduce or eliminate the complications of PROM and PTL associated with open fetal surgery, this supposition has not been realized clinically. The PROM rate even in single-port cases persists at 10% and is as high as 60% in multiple port cases (41,120). Similarly, PTL, although attenuated, persists as a threat to the more widespread application of MAFS and its extension to the application for non–life-threatening fetal abnormalities.