Prospective risk of intrauterine fetal death in monoamniotic twin pregnancies.

This study was conducted to review the overall short-term outcome of monoamniotic twins in Japan and to determine the prospective risk of fetal death so as to adequately counsel parents with monoamniotic twins. Study subjects were 101 women with monoamniotic twins who were registered with the Japan Society of Obstetrics and Gynecology Successive Pregnancy Birth Registry System and who had given birth at ≥22 weeks of gestation during 2002-2009. The gestational week at delivery (mean±SD) was 31.8±3.7. Fourteen women experienced intrauterine fetal death (IUFD). Short-term outcomes of co-twins born to the 14 women included 8 IUFDs, one early neonatal death within 7 days of life (END), and 5 survivors. Four other women experienced 5 ENDs. Thus, 13.9% (28/202) of infants died perinatally (22 IUFDs and 6 ENDs), 13.9% (14/101) of women experienced IUFD, and 82.2% (83/101) of women experienced neither IUFD nor END. Structural anomalies and twin-to-twin transfusion syndrome explained 17.9% (five infants) and 10.7% (three infants) of the 28 perinatal deaths, respectively. The prospective risk of IUFD was 13.9% (14/101) for women who reached gestational week 22(-0/7), gradually decreasing thereafter but remaining at between 4.5% and 8.0% between gestational week 30(-0/7) and 36(-0/7).