The objective of this study was to determine the reference values for fetal heart functional measurements at 24 and 34 weeks of gestation and to develop Z-score equations for all measurements. A single-center, prospective, cross-sectional study with normal fetuses between 24 and 34 weeks of gestation was performed. All pregnant women underwent a comprehensive fetal Doppler echocardiogram with anatomical and functional analysis. Measurements of left and right cardiac output, combined cardiac output, mitral and tricuspid valve flow, inferior vena cava flow, and pulmonary vein flow were performed. The Shapiro-Wilk test and histogram evaluation were performed on all variables. Linear regression was used to assess the relationships between measurements and gestational age. A total of 612 pregnant women with singleton and normal fetuses were included. We assessed the reference values and percentiles of cardiac function as a function of gestational age. The variables that were not normally distributed were subjected to logarithmic or square root transformation. Eleven Z-score equations were developed, with equations for left and right ventricle output and combined cardiac output that were dependent on gestational age and with other equations that were independent of gestational age. The present study produced a large database, allowing the demonstration of reference values and percentiles as well as the development of Z-score equations to facilitate the echocardiographic evaluation of fetal heart function.
Keywords: Cardiac function; Fetal heart; Reference values; Two-dimensional echocardiography.