A new approach for quantitative assessment of fetal general movements in the early second trimester of pregnancy using four-dimensional ultrasound.

Purpose: Complex fetal behavior involving multiple parts of the body, called general movement (GM), has been considered an essential predictor of neurological functional development because it directly reflects the integrity of the brain and central and peripheral nervous systems. We have developed a novel method for quantitative analysis of fetal behavior using four-dimensional ultrasound (4DUS) and conducted a pilot study for quantitative assessment of fetal GM in the early second trimester.

Methods: All subjects underwent 4DUS to depict the whole fetal body, and maximum velocity (MAXV), median velocity (MV), average velocity (AV), and mode velocity (MOV) were calculated by utilizing optical flow analysis. Receiver operating characteristic (ROC) curve analysis was performed to analyze the optimal speed parameters for detecting GM in the fetus. The Mann-Whitney U test was used to validate MAXV, AV, and MV ability to detect fetal GM.

Results: The presence of fetal GMs and the absence of fetal GMs were 226 and 107, respectively, based on optical flow analysis. Mann-Whitney U test revealed a significant difference in the presence or absence of fetal GM in MAXV, MV, AV, and MOV. ROC analysis showed that the area under the curve (AUC) of MAXV was 0.959; the threshold was 0.421, the sensitivity was 86%, and the specificity was 93%. In contrast, the AUC/threshold for AV and MV was 0.700/0.110 (sensitivity 71% and specificity 76%) and 0.521/0.119 (sensitivity 21% and specificity 90%), respectively. Spearman's rank correlation analysis also showed a weak negative correlation between GM and MAXV (r = - 0.235, P < 0.01) and AV (r = - 0.28, P < 0.01).

Conclusion: In this study, we conducted a quantitative analysis of fetal behavior based on optical flow using 4DUS and demonstrated that it was highly accurate for detecting GMs and for evaluating developmental changes in GMs. The implementation of quantitative analysis of fetal GMs in the early second trimester has been very preliminary, and there is much debate on how it will be clinically applied to perinatal assessment.