Intertwin crown-rump length discordance in the prediction of fetal anomalies, fetal loss and adverse perinatal outcome

Objective: To assess the risks of fetal anomalies, fetal loss and adverse perinatal outcome in a cohort of first-trimester intertwin crown-rump length (CRL) discordant twins, stratified by chorionicity and the degree of CRL discordance.

Method: Four-hundred-and-seventy-one twin pregnancies were scanned during an 8-year period at 11-14 weeks, and those with an intertwin CRL discordance ≥10% were compared with concordant twins. Outcomes were also compared between monochorionic and dichorionic twins and between moderate (10-16%) and severe (>16%) discordance.

Results: Four-hundred-and-five twin pregnancies, 65 discordant and 340 concordant, were follow-up. Discordant twin pregnancies were at significant higher risk of chromosomal (OR = 11.42; 95% CI: 2.78-46.94) and structural anomalies (OR = 5.91; 95% CI: 2.25-15.54), spontaneous fetal loss (OR = 4.23; 95% CI: 1.79-10.01), birthweight discordance (OR = 2.8; 95% CI: 1.48-5.65) and small-for-gestational age (OR = 3.48; 95% CI: 1.78-6.79). Similar differences (except for birthweight discordance) were observed among dichorionic twins. Among monochorionic, increased frequencies were only seen for structural anomalies, birthweight discordance and small newborns. Severe CRL discordance presented with higher rates of structural anomalies, stillbirth, birthweight discordance and small newborns.

Conclusion: Intertwin CRL discordance (≥10%) results in an increased risk of fetal anomalies and growth restriction that increases in severe CRL discordance (≥16%).