Mild Fetal Tricuspid Regurgitation in the First Trimester as a Predictor of Perinatal Outcomes.

: This study aimed to investigate whether mild fetal tricuspid regurgitation (TR) at 11 to 13 weeks of gestation affects perinatal outcomes. Since fetal right ventricular load is associated with placental resistance, we hypothesized that fetal mild TR would be associated with perinatal outcomes as a consequence of abnormal placentation. : We retrospectively evaluated 435 women with first-trimester scan data. Blood flow across the tricuspid valve was examined in singleton pregnancies between 11 and 13 weeks of gestation. Women were categorized according to the presence or absence of fetal mild TR, and the maternal and pregnancy characteristics and perinatal outcomes were compared. Multiple linear and logistic regression analyses were conducted to identify independent predictors of perinatal outcome. : In the group with mild TR, there were more cases of borderline amniotic fluid index, including oligohydramnios ( = 0.031), and gestational age- and sex-specific birth weights were lower ( = 0.012). There were no significant differences in other perinatal outcomes, including preeclampsia, gestational hypertension and small for gestational age. Gestational diabetes (adjusted odds ratio (OR) 0.514, 95% confidence interval (CI) 0.312-0.947) and fetal mild TR (adjusted OR 1.602, 95% CI 1.080-2.384) were identified as factors associated with below borderline amniotic fluid index before birth. The factors that affected gestational age and sex-specific birth weight were also gestational diabetes (adjusted beta coefficient 9.673, = 0.008) and the presence of fetal mild TR (adjusted beta coefficient -6.593, = 0.007). : Mild fetal TR observed in the first trimester is negatively associated with fetal growth and the amniotic fluid index at term but not with other adverse pregnancy or perinatal outcomes due to abnormal placentation.