To evaluate the diagnostic value of the normal reference range obtained by two-dimensional axial planes in abnormal fetal corpus callosum.

Between June 2018 and July 2020, 670 normal and 77 abnormal fetuses at a gestational age of 20 weeks to full term were evaluated by two-dimensional axial planes at Shenzhen Maternity & Child Healthcare Hospital, Southern Medical University. The diagnosis of abnormal fetuses was confirmed by pre-natal MRI/post-natal ultrasound/ autopsy examinations. The abnormal fetuses were divided into four groups: complete agenesis of the corpus callosum, partial agenesis of the corpus callosum, hypoplasia of the corpus callosum, and hypoplasia of the corpus callosum. The largest length of the corpus callosum, the anteroposterior and mediolateral diameters of the genu, body, and splenium, and anterior and posterior angles of the genu and splenium were measured. Non-parametric test was used to compare the parameters between the normal and abnormal groups, and compound scatter plots of all parameters were drawn.

There was no significant difference in maternal age [30 (28, 33) years vs 30 (26, 34) years] and gestational weeks [28 (24, 32) weeks vs 25 (23, 28) weeks] between the 670 normal pregnant women and the 77 abnormal pregnant women (P＞0.05). In the normal group, the success rate in obtaining satisfactory axial planes reached 100%, but it was only 13.9% in obtaining satisfactory sagittal planes in the normal group; the corresponding figures in the abnormal cases were 100% and 62.3%. The anterior and posterior angles of the genu, anterior and posterior angles of the splenium, anteroposterior diameter of the genu, the largest length of the corpus callosum, mediolateral diameter of the genu, anteroposterior diameter of the splenium, anteroposterior diameter of the splenium, mediolateral diameter of the body, and anteroposterior diameter of the body in the abnormal group were significantly lower than those in the normal group [48.00° (0°, 80.68°) vs (66.76°±10.79°); 44.00° (0°, 79.30°) vs 65.10° (49.30°, 83.00°); 41.90° (0°, 69.37°) vs (64.31°±10.27°); 38.50° (0°, 72.10°) vs (65.38°±11.65°); 0.21 (0, 0.40) cm vs (0.44±0.09) cm; 1.10 (0, 2.78) cm vs 3.33 (2.11, 4.20) cm; 1.18 (0, 2.23) cm vs 1.81 (1.22, 2.46) cm; 1.21 (0, 2.20) cm vs (2.02±0.40) cm; 0.18 (0, 0.35) cm vs 0.45 (0.32, 0.63) cm; 0.42 (0, 1.01) cm vs 0.62 (0.40, 0.98) cm; and 0.75 (0, 1.87) cm vs (1.86±0.33) cm, respectively] (Z=-8.959, -8.650, -9.839, -9.993, -12.812, -13.668, -7.343, -10.521, -12.145, -5.260, and -14.034, respectively, P＜0.001). The compound scatter plots showed that the largest length of the corpus callosum was significantly shorter, and the thickness of the genu and splenium with HpCC (thin) was significantly lower in abnormal fetuses than in normal fetuses, showing the parameter measurements below the 5th percentile line of normal values. There was no significant difference in other parameters on the compound scatter plots.

Prenatal two-dimensional axial planes can well evaluate the corpus callosum structure, which is valuable for the evaluation of fetuses with abnormal corpus callosum. In particular, the largest length of the corpus callosum is suitable for the evaluation of most abnormal corpus callosum cases. The anteroposterior diameters of the genu and splenium are useful for the diagnosis of HpCC (thin). Other parameters are of little significance for the diagnosis of corpus callosum abnormalities.