Fetal intracranial anatomy in the first trimester of pregnancy: transvaginal ultrasonographic evaluation.

The normal values and ranges of fetal intracranial structures were studied by high resolution transvaginal ultrasonic scan at 12, 13 and at 14 weeks' gestation. The data including measurements of crown rump length (CRL), bi-parietal diameter (BPD), head circumference (HC), hemispheric width (HW), lateral ventricle width (LVW), LVW/HW ratio, thalamus and cerebellum may be useful in determining deviations from the normal and also in expanding the range of prenatal diagnoses of fetal structural abnormalities in early pregnancy.