Fetal 24-Segment Sphericity Index and Ventricular Fractional Shortening Between 12 and 20 Weeks of Gestation

Although the fetal sphericity index (SI) and fractional shortening (FS) of 24 transverse segments have been previously reported after the 20th gestational week, there have been no reports during the first and early second trimester.

This study aimed to clarify the SI and FS of 24 transverse segments in normal fetuses before the 20th gestational week.

A total of 101 normal fetuses aged between 12 and 20 gestational weeks were examined. The displacement of the ventricular endocardium during the cardiac cycle was computed using speckle-tracking software (GE Healthcare, Milwaukee, WI). We analyzed the length of 24 end-diastolic lateral segments and the end-diastolic basal (seg1-6)- middle (Seg7-15)-apical (Seg16-24) distribution from the base to the apex of each ventricle, according to the method described by DeVore et al. The SI and FS were computed for each of the 24 segments by dividing the mid-basal-apical length by the transverse size.

The SI for each segment was independent of the gestational age. The SI of the right ventricle was significantly lower than that of the left ventricle for segments 1-14, suggesting that the right ventricle was more spherical than the left ventricle in the basal segment only. The FS of the right ventricle was significantly lower than that of the left ventricle in segments 1 to 2 and 13 to 24.

The morphology of the ventricles before 20 weeks of gestation differs from that between 20 and 40 weeks of gestation. This difference may be related to myocardial densification or performance.