Objective. We investigated the utility of analyzing prenatal mediastinal measures of the great arteries in distinguishing true coarctation of the aorta (CoA) from false‐positive CoA. Methods. All fetuses in this study had suspicion of CoA based on the presence of right‐left heart disproportion. We defined 3 study groups: group 1, true fetal CoA; group 2, false‐positive fetal CoA with a narrow aortic arch; and group 3, false‐positive fetal CoA without a narrow aortic arch. Results. In group 1, the mean mediastinal pulmonary artery (PA) to ascending aorta (Ao) diameter ratio ± SD was 2.03 ± 0.48, and in group 2, the ratio was 1.60 ± 0.23. The difference was statistically significant (P = .0018, t test). In group 3, the mean PA:Ao ratio was 1.35 ± 0.14. The difference between groups 1 and 3 was statistically significant (P = .0002, t test). In our study group, for a PA:Ao ratio of 1.60, sensitivity was 83.0%; specificity, 85.0%; positive predictive value, 62.5%; and negative predictive value, 94.0%. Conclusions. In the third trimester, the main PA:Ao ratio as measured in the fetal mediastinum can be a helpful tool in distinguishing true CoA requiring neonatal cardiac surgery from false‐positive CoA and simple disproportion requiring medical attention but no surgery in the first month of postnatal life.

Background: Altered cardiac geometry affects a proportion of fetuses with growth restriction (FGR). The aim of this study was to explore the hemodynamic factors associated with cardiac remodeling in late FGR. Methods: This was a prospective study of singleton pregnancies complicated by late-onset FGR undergoing assessment of left (LV) and right (RV) ventricular sphericity-index (SI). The study population was divided in two groups according to the presence of cardiac remodelling, defined as LVSI <5^th centile. The following outcomes were explored: gestational age at birth, birthweight, caesarean section (CS) for fetal distress, umbilical artery (UA) pH and neonatal admission to special care unit. The differences between the 2 groups in UA pulsatility index (PI), middle cerebral artery (MCA) PI, uterine artery PI, cerebroplacental ratio (CPR) and umbilical vein (UV) flow corrected for fetal abdominal circumference (UVBF/AC) were tested. Results: In total, 212 pregnancies with late FGR were enrolled in the study. An abnormal LV SI was detected in 119 fetuses (56.1%). Late FGR fetuses with cardiac remodeling had a lower birthweight (2390 g vs. 2490; P = 0.04) and umbilical artery pH (7.21 vs. 7.24; P = 0.04) and were more likely to have emergency CS (42.8% vs. 26.9%; P = 0.023) and admission to special care unit (13.4% vs. 4.3%; P = 0.03) compared to those with normal LVSI. No difference in either UA PI (p = 0.904), MCA PI (P = 0.575), CPR (P = 0.607) and mean uterine artery PI (P = 0.756) were present between fetuses with or without an abnormal LV SI. Conversely, UVBF/AC z-score was lower (−1.84 vs. −0.99; P ≤ 0.001) in fetuses with cardiac remodeling and correlated with LV (P ≤ 0.01) and RV SI (P ≤ 0.02). Conclusion: Fetal cardiac remodelling occurs in a significant proportion of pregnancies complicated by late FGR and is affected by a high burden of short-term perinatal compromise. The occurrence of LV SI is independent from fetal arterial Dopplers while it is positively associated with umbilical vein blood flow.