Biometry of the fetal corpus callosum by three-dimensional ultrasound.

OBJECTIVES

To construct reference ranges of quantitative characteristics of the fetal corpus callosum.

METHODS

Women referred to a tertiary center for sonographic examination were recruited to undergo a detailed fetal scan from 17 to 41 weeks of gestation. Three-dimensional (3D) sonographic volumes of normal fetal brains were acquired and analyzed offline. We obtained three different measurements of the corpus callosal length, as well as the height (/thickness) of its segments, namely the rostrum, genu, body and splenium.

RESULTS

Initially we recruited 604 pregnant women, of whom 138 were excluded because of various disorders/abnormalities, multiple pregnancy or gestational age < 18 weeks. Thus, included in the analysis were 466 sonographic volumes of normal fetal brains from singleton pregnancies, acquired by transabdominal ( n = 170) or transvaginal (n = 296) ultrasound. The corpus callosum was visualized as a hypoechoic structure. Reference ranges were established for the following parameters: curved corpus callosal length, inner-inner corpus callosal length, outer-outer corpus callosal length, rostrum height, genu height, body height and splenium height. We observed non-linear growth and an approximately four-fold increase in all corpus callosal lengths, a three-fold increase in rostrum height, a four-fold increase in genu height, a two-fold increase in body height and a three-fold increase in splenium height between 18 and 41 weeks. The growth patterns of rostrum and body height appeared to be similar: there was rapid development until 24 and 22 weeks of gestation, respectively, and growth slowed beyond this period. The growth patterns of genu and splenium were also similar, being characterized by progressive growth throughout gestation.

CONCLUSIONS

Using 3D ultrasound, we have constructed reference charts for measurements of the corpus callosum. Knowledge of the normal growth pattern may be useful for evaluation of abnormal development of the corpus callosum, and so help in the accurate diagnosis of pathologies such as hypogenesis and dysgenesis.