Intertwin discordance in fetal size at 11-13 weeks' gestation and pregnancy outcome.

In both DC and MCDA twin pregnancies, increased CRL discordance is associated with an increased risk of fetal death at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm birth at < 37 and < 32 weeks, birth of at least one SGA neonate and birth-weight discordance ≥ 20% and ≥ 25%, but CRL discordance is a poor screening test for adverse pregnancy outcome. However, in DC twins, CRL discordance of ≥ 15% is associated with an increased risk of fetal loss at < 20 and < 24 weeks' gestation and, in MCDA twins, CRL discordance of ≥ 10%, and more so discordance of ≥ 15% and ≥ 20%, is associated with a very high risk of fetal loss or endoscopic laser surgery at < 20 and < 24 weeks and this information is useful in counseling women and defining the timing for subsequent assessment and possible intervention. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.