GENDER DIFFERENCES IN TWIN-TWIN TRANSFUSION SYNDROME

Objective: To determine whether there is a gender discrepancy in sever e twin-twin transfusion syndrome. Methods: All cases of twin-twin tran sfusion syndrome evaluated between 1989 and 1996 were reviewed retrosp ectively. The following sonographic criteria were used: a single place nta, a thin membrane, the same gender, a combination of polyhydramnios -oligohydramnios, a stuck twin, and an estimated weight discordance ex ceeding 20%. At least five of six sonographic criteria were required f or inclusion in the study. Only severe cases, which were defined as ea rly onset (before 30 weeks' gestation), a combination of polyhydramnio s and oligohydramnios, a stuck twin, fetal hydrops, fetal death, or th e requirement of medical or invasive treatment, were included. Chorion icity was confirmed by placental examination when available. Results: Thirty-seven twin pregnancies met the above criteria, of which 33 (89% ) twin pairs were female. The median gestational age at presentation w as 19 weeks (range, 15-29; standard deviation, 5.6). A single placenta , thin membrane, same gender, and polyhydramnios-oligohydramnios were present in every case. A stuck twin was noted in 34 of 37 cases (92%), and a growth discordance exceeding 20% was present in 26 of 36 (72%), Placental pathology, which was available in 31 (84%) cases, confirmed a monochorionic placentation in 29. Twenty-five (68%) cases had reduc tion amniocentesis, two were treated with indomethacin, one underwent a cord ligation, and in four cases, fetal death occurred before treatm ent was instituted. Conclusion: There is a significant female preponde rance in pregnancies complicated by severe twin-twin transfusion syndr ome. The reasons for this are unclear, but they may be related to eith er placental or fetal gender-specific differences affecting a subset o f monochorionic twin pregnancies. (C) 1997 by The American College of Obstetricians and Gynecologists.