Septostomy

TTTS. Septostomy

The rationale on the use of septostomy or dividingmembrane amniorrhexis for the treatment of TTTS was to equilibrate the amniotic pressures on both sides of the membrane.10,11 Prior to its proposal, a difference in amniotic fluid pressures in the two sacs was never demonstrated. 

On the contrary, Quintero and others showed that, in fact, the pressure in both sacs is similar.12,13 Notwithstanding, a randomized controlled trial was carried out to compare septostomy versus amnioreduction.14 The study was terminated at the planned interim analysis stage after 73 women were enrolled. 

This was because the rate of survival of at least 1 infant was similar in the amnioreduction group compared with the septostomy group (78% vs 80% of pregnancies, respectively; RR = 0.94, 95% CI 0.55–1.61; p = 0.82). Patients undergoing septostomy were more likely to require a single procedure for treatment (64% vs 46%; p=0.04). Level of evidence: I. 

While the data clearly show no benefit of septostomy over serial amniocentesis, its complications have not been emphasized enough. Passive transfer of amniotic fluid from the sac of the donor to the recipient eliminates the possibility of monitoring improvement of the donor in terms of urine production. 

Septostomy may also make subsequent amniocenteses or laser difficult, as the dividing membrane interferes with the procedure (a finding perhaps reflected in the randomized clinical trial, but with a different explanation). Finally, septostomy may result in pseudomonoamniotic pregnancy, with demise of one or both fetuses from cord entanglement. Therefore, septostomy should not be used to treat TTTS.