Risk of preterm delivery and growth restriction in twins discordant for structural anomalies

Abstract

Objective: We sought to determine whether twin gestations with an anomalous fetus are at increased risk of preterm delivery or intrauterine growth restriction (IUGR) compared to twins with 2 normal fetuses.

Study design: This was a retrospective cohort of twins undergoing ultrasound 15-22 weeks' gestation. Groups were defined by the presence of 1 twin with a major anomaly (discordant) or by twins with no major anomalies (normal). The primary outcomes were preterm delivery (<37 weeks) and IUGR (<10th percentile).

Results: Of 1977 twin pregnancies, 66 had a twin with a major anomaly. Preterm delivery occurred in 42 (63.6%) discordant twins, compared to 1271 (66.5%) normal twins (risk ratio, 1.0; 95% confidence interval, 0.8-1.2). IUGR was diagnosed in 15 (22.7%) normal co-twins, compared to 406 (21.3%) presenting twins in normal twins (risk ratio, 1.1; 95% confidence interval, 0.7-1.7).

Conclusion: Twins discordant for major anomalies are not at increased risk of preterm delivery or IUGR compared to twins with no major anomalies.