Discordance of First-Trimester Crown-Rump Length Is a Predictor of Adverse Outcomes in Structurally Normal Euploid Dichorionic Twins

Objective. The purpose of this study was to determine the association between discordant crown-rump length (CRL) measurements in structurally normal euploid dichorionic twins and adverse pregnancy outcomes. Methods. This retrospective cohort study included women with dichorionic twins who underwent chorionic villus sampling and delivered in our facility from January 2000 to September 2007. Only pregnancies with viable twin fetuses and normal karyotypes were included. The association between CRL discordance, defined as a CRL discrepancy of 9% or greater, and adverse pregnancy outcomes was evaluated. Results. Seventy-eight women met inclusion criteria and included 24 discordant twins (group 1) and 54 concordant twins (group 2). Maternal ages were similar: mean SD, 38.2 +/- 3.1 years in group 1 versus 39.2 +/- 3.9 years in group 2 (P = not significant). The median gestational ages at delivery were 35.6 +/- 3.1 weeks in group 1 and 37.3 +/- 2.0 weeks in group 2 (P < .01). At least 1 major complication occurred in 19 women (79%) in group 1 and 25 (46%) in group 2 (P = .01). Group 1 had significantly more major complications overall (P = .0008). Preterm premature rupture of membranes occurred in 10 women (42%) in group 1 and 6 (11%) in group 2 (P = .005). Delivery before 37 weeks' gestation occurred in 19 of 24 women (79%) in group 1 and 24 of 54 (44%) in group 2 (P = .006). There was a significant difference for younger gestational age at delivery in the discordant group (P < .01). Conclusions. Our data suggest that there is an increased risk of adverse pregnancy outcomes in chromosomally normal dichorionic twins with first-trimester discordant CRL measurements. These results may be clinically useful for counseling, management, and antenatal surveillance.