Fetal cerebral ventricular atrium: difference in size according to sex

To determine whether the diameter of the fetal lateral ventricular atrium is larger in male than in female fetuses.

The atrial diameter in 219 fetuses retrospectively identified from a consecutive group of healthy newborns was measured without knowledge of the subject's sex.

Atrial size demonstrated a near-normal distribution, with mean size for all subjects 6.1 mm +/- 1.3 (standard deviation). When separated by sex, the mean atrial diameter of 122 female fetuses was 5.8 mm +/- 1.3, and the mean atrial diameter of 97 male fetuses was 6.4 mm +/- 1.3. The difference in mean size is statistically significant (P < .005).

Male fetuses have a slightly larger atrial size than female fetuses. This discovery has implications for defining the upper limit of normal for fetal ventricular atrial size.