First-Trimester Growth Rate in Relation to Selective Fetal Growth Restriction in Monochorionic Twins

Crown-rump length discrepancy (CRLd) is commonly used to predict selective fetal growth restriction (sFGR) in monochorionic diamniotic (MCDA) twins, but its predictive value is limited. This study aimed to determine whether a first-trimester growth rate (GR) variable is associated with later sFGR.

Retrospective cohort included MCDA-twin pregnancies with first-trimester ultrasound data. CRLd was calculated for each fetus dividing the delta CLR by the bigger CRL; GR was calculated for each fetus dividing CRL by gestational age. Pregnancies were classified as normal and sFGR. Generalized estimating equations were used to evaluate the independent associations of GR and CRLd with sFGR.

Among 335 pregnancies, 235 (70.1%) were normal, and 100 (29.85%) were sFGR. GR was lower in pregnancies that developed sFGR and differed within sFGR pairs. Pearson's correlation showed no significant relationship between GR and CRLd. After accounting for co-twin correlation, both lower GR and higher CRLd were independently associated with higher odds of sFGR.

Reduced first-trimester GR and increased CRLd are independent early indicators of sFGR, and their combined assessment yields the best model fit.