Objective: Pregnant women with congenital heart disease (CHD) have an increased risk of abnormal uteroplacental flow, measured from the second trimester onwards, which is associated with pregnancy complications affecting the mother and the fetus. Maternal right ventricular (RV) dysfunction has been suggested as a predisposing factor for impaired uteroplacental flow in these women. The aim of this study was to investigate the association of first-trimester uteroplacental flow measurements with prepregnancy maternal cardiac function and pregnancy complications in women with CHD, with particular focus on the potential role of RV (dys)function. Methods: This study included 138 pregnant women with CHD from the prospective ZAHARA III study (Zwangerschap bij Aangeboren HARtAfwijkingen; Pregnancy and CHD). Prepregnancy clinical and echocardiographic data were collected. Clinical evaluation, echocardiography (focused on RV function, as assessed by tricuspid annular plane systolic excursion (TAPSE)) and uterine artery (UtA) pulsatility index (PI) measurements were performed at 12, 20 and 32 weeks of gestation. Univariable and multivariable regression analyses were performed to assess the association between prepregnancy variables and UtA-PI during pregnancy. The association between UtA-PI at 12 weeks and cardiovascular, obstetric and neonatal complications was also assessed. Results: On multivariable regression analysis, prepregnancy TAPSE was associated negatively with UtA-PI at 12 weeks of gestation (β = −0.026; P = 0.036). Women with lower prepregnancy TAPSE (≤ 20 mm vs > 20 mm) had higher UtA-PI at 12 weeks (1.5 ± 0.5 vs 1.2 ± 0.6; P = 0.047). Increased UtA-PI at 12 weeks was associated with obstetric complications (P = 0.003), particularly hypertensive disorders (pregnancy-induced hypertension and pre-eclampsia, P = 0.019 and P = 0.026, respectively). Conclusions: In women with CHD, RV dysfunction before pregnancy seems to impact placentation, resulting in increased resistance in UtA flow, which is detectable as early as in the first trimester. This, in turn, is associated with pregnancy complications. Early monitoring of uteroplacental flow might be of value in women with CHD with pre-existing subclinical RV dysfunction to identify pregnancies that would benefit from close obstetric surveillance. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.