First-trimester fetal growth discordance and development of preeclampsia in dichorionic twin pregnancies.

Objective: To investigate the relation between first-trimester fetal growth discrepancy, as assessed by crown-rump length (CRL) at 11+0 to 13+6 weeks of gestation, and subsequent development of preeclampsia (PE) in dichorionic diamniotic (DCDA) twin pregnancies. The association between inter-twin CRL and birth weight (BW) discrepancy was also investigated.

Methods: This was a retrospective, case-control study of DCDA twin pregnancies. Inter-twin CRL discrepancy was calculated as 100×(larger CRL-smaller CRL)/larger CRL. BW discordance was calculated as 100×(larger BW-smaller BW)/larger BW.

Results: The study included 299 DCDA pregnancies that remained normotensive and 35 that subsequently developed PE. There was no significant difference in the inter-twin CRL discrepancy between pregnancies complicated by PE and those that were not [3.2%, interquartile range (IQR): 0.5-4.5% vs. 3.3%, IQR: 1.4-5.5%; P=0.17]. There was a positive correlation between inter-twin CRL and BW discrepancy but only in pregnancies that remained normotensive (P<0.001). In women that subsequently developed PE, there was no association between inter-twin CRL and BW discordance (P=0.54).

Conclusions: In unselected DCDA twins, first-trimester CRL discrepancy is not different between pregnancies that subsequently develop PE and those that remain normotensive. Furthermore, in pregnancies that are complicated by PE, the association between inter-twin CRL and BW discrepancy appears to be lost.