Objectives: The purpose of this study was to investigate the association between first-trimester uterine artery pulsatility index (UtA-PI) and crown-rump length discordance (CRLD) with growth discordance (GD) in twins and analyze the influence of chorionicity in these parameters.
Methods: This retrospective analysis integrated data from the twin pregnancy database of Centro Hospitalar São João (2019-2023), including 184 fetuses, with 19 monochorionic and 73 dichorionic gestations. To determine the association between UtA-PI and CRLD with GD, correlation analyses were computed and linear regression models were carried out. Separate analyses were conducted for each type of placentation. Logistic regression analysis was carried out to determine the association of mean UtA-PI and CRLD with severe GD, defined as discordance ≥25 %.
Results: GD≥25 % was detected in 9.80 % of pregnancies. A statistically significant difference between monochorionic and dichorionic gestations was found in crown-rump length (p=0.009), CRLD (p<0.001) and birth weight (p=0.025), but not in mean UtA-PI (p=0.853) or GD (p=0.556). Mean UtA-PI was significantly higher in discordant than in concordant pairs (p<0.001), but that association was not seen in CRLD (p=0.931). Mean UtA-PI and GD were correlated by the regression line "GD=3.844 × UtA-PI + 6.638", with R2 0.027. CRLD and GD were correlated by the regression line "GD=0.280 × CRLD + 10.79", with R2 0.010. Mean UtA-PI, but not CRLD, was significantly associated with severe GD (odds ratio, 22.753; p=0.002).
Conclusions: Mean UtA-PI, but not CRLD, is associated with GD. The prevalence of severe GD increases significantly with increasing mean UtA-PI.
Keywords: birth weight discordance; chorionicity; crown-rump length; fetal growth; twin pregnancy; uterine artery Doppler.
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