Supplementary Material for: Is Cardiomegaly an Indication of “Heart-Sparing Effect” in Small Fetuses?

Introduction: This study aimed to test the hypothesis that cardiac size is maintained in small fetuses presenting with cardiomegaly. Materials and Methods: We identified singleton fetuses with estimated fetal weight Z-scores for cardiac and thoracic circumferences normalized for gestational age (GA), biparietal diameter (BPD), head circumference (HC), and femur length (FL), obtained from 188 normally grown fetuses. Results: When comparing chest size, small fetuses had significantly lower thoracic circumferences median Z-scores (IQR) for GA = −4.82 (−6.15 to −3.51), BPD = −2.42 (−4.04 to −1.48), HC = −2.72 (−4.53 to −1.90), and FL = −1.60 (−2.87 to −0.71); p Z-scores (IQR) for GA = −1.59 (−2.79 to −0.16); p Z-scores for BPD = 0.29 (−0.65 to 1.28); p = 0.284 and HC = 0.11 (−1.13 to 0.96); p = 0.953, and higher cardiac circumferences Z-scores for FL = 0.94 (−0.05 to 2.13); p Conclusions: Our results show that in small fetuses with cardiomegaly, the heart maintains normal dimensions when normalized to cranial diameters and higher dimensions when normalized to long bones. This provides insight into cardiac adaptation to adverse intrauterine environment.