Cloacal exstrophy variants. Can blighted conjoined twinning play a role?

Purpose: For normal single births with evidence of first trimester twinning, vanishing twin rates of 13% to 78% have been reported. We propose that blighting of a conjoined twin can result in an infant with a variation of cloacal exstrophy. Materials and Methods: We retrospectively reviewed the records of 26 patients with cloacal exstrophy treated from January 1989 to November 2003, all of whom had prenatal evaluations readily available to determine the presence of twinning. The criterion for establishing the prenatal diagnosis of twins was the documentation of 2 fetal heart tones on Doppler and/or 2 fetal poles on ultrasound. Results: All 26 patients had prenatal care including prenatal fetal Doppler studies and followup ultrasound. Of the patients 15 had classic cloacal exstrophy (58%) with no evidence of twin gestations documented. Of the 26 cloacal exstrophy cases 11 (42%) were cloacal exstrophy variants, including 8 of the 11 (73%) with consistent findings of twin gestation on prenatal studies. All 8 patients had documented 2 fetal heart tones in the first trimester, and 4 had 2 fetal poles in 1 amniotic sac on prenatal ultrasound. Five patients had subsequent ultrasound studies showing a single fetus by the second trimester. Two patients were born conjoined with 1 of the twins lifeless at birth in both cases. Conclusions: We propose that blighted conjoined twinning may be a cause of cloacal exstrophy variant cases.