Normalization of amniotic fluid levels after fetoscopic laser surgery for twin-twin transfusion syndrome.

Objective: The purpose of this study was to describe amniotic fluid (AF) normalization after laser surgery for twin-twin transfusion syndrome (TTTS).

Methods: Patients with TTTS (n = 174) who had laser surgery from 2006 through 2009 underwent serial measurements of the AF maximum vertical pockets (MVPs) during postoperative weeks 1 through 10. A normal MVP was defined as greater than 2 cm and less than 8 cm. Postoperative TTTS criteria required an MVP of 2 cm or less in one sac and 8 cm or greater in the other sac. Patients with septostomy, immediate fetal death, or missing MVP values were excluded.

Results: Inclusion criteria were met by 115 patients. Normalization of the MVP occurred by week 5 in donors and week 8 in recipients in approximately 95% of the cases. Recipient fetuses with Quintero stage 3 or 4 TTTS (J Perinatol 1999; 19:550-555) were more likely to have an abnormal MVP than those with stage 1 or 2 TTTS during weeks 3 and 4 (P = .0049) and 5 and 6 (P = .0239). The criteria for TTTS were met in 6 cases (6.9%) in week 1: 5 resolved spontaneously, and 1 (1.2%) had persistent TTTS and required a second laser surgery. After week 1, 6 additional patients had abnormal MVP values for both fetuses simultaneously: 1 met TTTS criteria in week 3; 2 had oligohydramnios in week 2; and 3 had polyhydramnios in weeks 2, 4, and 7; none of these patients required further interventions.

Conclusions: Although the AF of individual donor and recipient fetuses may take several weeks to normalize after laser surgery for TTTS, it is rare for both fetuses to meet TTTS criteria beyond the first postoperative week.