Monoamniotic twins: case series and proposal for antenatal management

To present a case series of antenatally suspected monoamniotic twin gestations managed by a similar set of guidelines.

Eight women with antenatally suspected monoamniotic twins were identified between 1994 and 1996 in a single perinatal referral area. All were diagnosed sonographically. Management included serial ultrasound studies, frequent nonstress testing, and weekly steroid therapy. Elective cesarean delivery was recommended at 32 weeks unless obstetrically indicated at an earlier age.

Monochorionic monoamniotic twins were confirmed at delivery in six women, and one had a pseudomonoamniotic twin. One woman was found to have a monochorionic diamniotic pregnancy at delivery. Of the eight women, three were delivered by elective cesarean at 32 weeks, including the falsely diagnosed case. Three were delivered before 32 weeks because of nonreassuring fetal testing. One was delivered at 25 weeks secondary to hemolysis, elevated liver enzymes, low platelets, and disseminated intravascular coagulation. One was delivered at 33 weeks, after declining elective delivery at 32 weeks, because of death of one twin and nonreassuring testing of the other twin. Morbidity among the live-born infants included severe bronchopulmonary dysplasia (25-week twins), large-bowel perforation (30-week infant), and respiratory distress syndrome and mild bronchopulmonary dysplasia (one 32-week pair).

Monoamniotic twin pregnancies can be diagnosed reliably by ultrasound alone in most cases. Frequent antenatal testing may show signs of cord compression that may prompt delivery but will not prevent sudden fetal death. Fetal death can occur at greater than 32 weeks' gestation despite intensive fetal surveillance. Elective preterm delivery could be considered to eliminate the uncertain risk of fetal death.