Transabdominal Sonographic Study of the Cavum Vergae Detection Rate in Healthy Third-Trimester Fetuses

We aimed to measure the thickness and volume of the cavum vergae by sonography in fetuses at gestational ages of 25 to 41 weeks to determine the relationship of cavum vergae thickness and volume with gestational age and biparietal diameter and to estimate the rate of cavum vergae closure in relation to gestational age.

A total of 336 patients in their third trimester of pregnancy had transabdominal sonography. The fetal cavum vergae was scanned in the coronal and axial planes. The thickness of the anteroposterior diameter of the cavum vergae and the largest inner surface were measured after marking the internal borders of the structure, and then longitudinal and vertical sizes were obtained. The values obtained were multiplied by each other and then by 0.52 to obtain the cavum vergae volume.

In 55 of 322 cases, the cavum vergae volume and thickness could not be calculated because the cavum vergae was closed. In the remaining cases, the cavum vergae volume and thickness and biparietal diameter were measured. Although the degree of correlation between cavum vergae thickness and volume increased with increasing gestational age, there was no correlation between cavum vergae thickness and volume at 37 to 41 weeks. There was a positive but weak statistically significant correlation between biparietal diameter and cavum vergae volume (P= .05), but there was no statistically significant correlation between biparietal diameter and cavum vergae thickness. The cavum vergae closure rate increased significantly as gestational age increased (P < .001).

Cavum vergae closure increases as gestational age increases. However, we did not find any relationships between cavum vergae thickness and volume, gestational age, and biparietal diameter.