Until the 1980s, physicians had few options for parents of fetuses with congenital malformations; essentially, these were to terminate the pregnancy or continue and possibly modify the timing and/or method of delivery. Rapid advances in prenatal imaging and diagnosis over the last 20 years, coupled with increased understanding of the natural history of many fetal anomalies, has led to the identification of the fetus as a patient and to the burgeoning field of fetal surgery. An increasing number of selected fetal anomalies are amenable to prenatal intervention (Table 73.1), yet it has been difficult to demonstrate efficacy with regard to improved outcomes. With the exception of myelomeningocele and twin–twin transfusion syndrome, anomalies amenable to fetal repair yield only 2–5 cases per year at the busiest fetal treatment centers. Thus, the dearth of patient volume has dictated that outcome assessment be done over a long time often using historical controls. Also, anomalies in which no prenatal treatment reliably results in fetal death (e.g., lung lesion producing hydrops) cannot be ethically “randomized” for prospective study. Randomized prospective trials have been done for several “high” volume anomalies. To date, there are two completed randomized trials for congenital diaphragmatic hernia, and there are ongoing prospective randomized trials for myelomeningocele and twin–twin transfusion syndrome, each of which is illustrated below.

Risks and benefits

Assessing risks and benefits in fetal surgery is a complex task. Both the fetus and the mother must be considered.