Z-score reference ranges for normal fetal heart sizes throughout pregnancy derived from fetal echocardiography

To construct Z-score reference ranges for normal fetal heart sizes throughout pregnancy.

This is a prospective cross-sectional investigation of 809 normal singleton fetuses from 11th week to term. Fetal transverse heart diameter (HD), heart length (HL), heart circumference (HC) and heart area (HA) were derived from two-dimensional echocardiography. The regression analyses of the mean (M) and the standard deviation (SD) for each parameter were calculated separately, using fetal somatic sizes as independent variables. A group of fetal heart diseases was assessed using these parameters.

Strong correlations were found between fetal heart sizes and somatic sizes. Linear-cubic regression equations were each fitted to the models of the means of the heart sizes, whereas linear-quadratic equations were fitted to the models of the SDs. HD was the dependent variable that provided the highest correlation coefficient with all of the fetal sizes, followed by HL, HC and HA. All fetuses with Ebstein's anomaly and most with homozygous α-thalassemia-1 demonstrated Z-scores reflective of increased heart sizes.

The calculation of Z-scores for heart sizes as a function of fetal somatic size is simple and may be useful for quantitative assessment of some cardiac diseases, particularly cardiomegaly caused by homozygous α-thalassemia-1.