Midtrimester isolated polyhydramnios in monochorionic diamniotic multiple gestations

Objective To identify risk factors for development of twin-twin transfusion syndrome (TTTS) in monochorionic diamniotic multiple gestations complicated by midtrimester isolated polyhydramnios (iPoly). Study Design A retrospective study of patients referred for possible TTTS between 16 and 26 gestational weeks was performed. IPoly was defined as a maximum vertical pocket of ≥8 cm in the iPoly twin's sac and >2 and <8 cm in the co-twin's sac on the consultative ultrasound. Results Of 628 consecutive patients referred for possible TTTS, 74 were diagnosed with iPoly. The majority of these patients (n = 52, 70.3%) were not subsequently diagnosed with TTTS, and of these, 40 were managed expectantly and 12 had amnioreductions because of symptomatic iPoly; 30-day perinatal survival of at-least-one twin in the non-TTTS group was 93.0% (40/43). TTTS developed in the 22 remaining patients, of which 63.6% were of advanced Quintero Stage. Nineteen underwent laser surgery; 30-day perinatal survival of at-least-one twin was 84.2% (16/19). In a multivariate logistic regression model, 2 characteristics were associated with the development of TTTS: (1) gestational age <20 weeks at the time of diagnosis of iPoly (odds ratio, 13.48; 95% confidence interval, 3.40-53.48; P =.0002); and (2) intrauterine growth restriction of the co-twin (odds ratio, 7.28; 95% confidence interval, 1.72-30.88; P =.0071). Conclusion Among referred patients with midtrimester iPoly, 29.7% subsequently developed TTTS. Early diagnosis (<20 weeks) and/or co-twin intrauterine growth restriction were significant risk factors for development of TTTS in these patients.