Fetal Growth Disorders in Dichorionic Diamniotic IVF Twin Pregnancies: A Retrospective Longitudinal Cohort Study

Abstract

Growth disorders are common in in vitro fertilization (IVF)-conceived twins, but risk factors specific to dichorionic-diamniotic twins remain incompletely characterized. This study aimed to assess these risk factors. Data from in vitro fertilization pregnancies (December 2020 – November 2024) were retrospectively analyzed. Small for gestational age was defined as estimated fetal weight below the 10th percentile. Intertwin discordance greater than 15% was considered significant. Change in uterine artery pulsatility index was calculated by subtracting first-trimester from second-trimester values. Of 169 dichorionic-diamniotic twin pregnancies, 30 (17.8%) were from fresh embryo transfer and 139 (82.2%) from frozen embryo transfer. Mean uterine artery pulsatility index was higher in the fresh group in both trimesters (first: 1.72 vs. 1.30; second: 0.91 vs. 0.78; both p = .001). Small for gestational age incidence was similar between groups (56.7% vs. 50.3%, p = .441), as was significant discordance (36.6% vs. 25.9%, p = .081). Logistic regression identified advanced maternal age (odds ratio: 1.07, 95% CI [1.00, 1.14]; p = .024), higher first-trimester uterine artery pulsatility index ( OR 2.19, 95% CI [1.27, 3.76]; p = .002), and preeclampsia ( OR 3.74, 95% CI [1.19, 11.67]; p = .023) as predictors of small for gestational age. For significant discordance, predictors were second-trimester intertwin estimated fetal weight difference ( OR 1.03, 95% CI [1.01, 1.04]; p = .001) and change in uterine artery pulsatility index (odds ratio: 2.51, 95% CI [1.01, 6.22]; p = .047). Uterine artery pulsatility index and second-trimester biometric differences independently predict small for gestational age and intertwin discordance in IVF-conceived dichorionic-diamniotic twin pregnancies.