RESULTS
Six hundred and twenty-eight twin deliveries occurred in the
University of California, San Diego Health System, over the 13-year
study period. Of these deliveries, 489 (78%) met criteria for
inclusion. Maternal characteristics of the study population are
presented in Table 1. Of the 489 included pregnancies, chorionicity
was confirmed by placental pathology in 90.2% (444/489) of
the cases.