Monochorionic monoamniotic twins: neonatal outcome.

BACKGROUND

Monochorionic monoamniotic twins (MoMo) occur in one of 10,000 pregnancies. Cord entanglement, malformations, twin-to-twin transfusion syndrome (TTS) and prematurity are responsible for their high perinatal morbidity and mortality.

OBJECTIVE

To report our experience with 36 sets of MoMo twins (1990 to 2005) and to provide updated information for counseling.

METHODS

Chorionicity was determined by placental examination, gestational age and TTS clinically and by sonography. Intrauterine growth restriction (IUGR) was diagnosed with a twin-specific nomogram.

RESULTS

Cord entanglement was observed in 15 pregnancies, but only one twin with entanglement and a true knot, experienced related morbidity. Four of 71 live births were IUGR. Malformations were diagnosed prenatally (one hypoplastic left heart and one body stalk) and postnatally (one vertebral anomalies-anal atresia-tracheoesophageal fistula-renal defect (VATER) and two lung hypoplasias). Twin-to-twin transfusion syndrome affected three sets of twins. Five twin sets delivered before 31, 19 sets at 31 to 32 and 12 sets at 33 to 34 weeks. Six of 71 (8%) twins died (four malformations, one TTS and one 26 weeks premature). Head ultrasounds in 59 of 65 survivors showed two (3%) periventricular leukomalacia, five (9%) Grade I-II intraventricular hemorrhage and 52 (88%) normal.

CONCLUSIONS

Monochorionic monoamniotic twins remain a group at risk for cord entanglement, congenital malformations, TTS and prematurity. Although their neonatal mortality and morbidity is high, outcomes for survival are better than anticipated.