FETAL LITERAL VENTRICLES - REASSESSMENT OF NORMAL VALUES FOR ATRIAL DIAMETER AT US

PURPOSE: To assess the normal range of,cerebral ventricular atrial dia meters during the second and third trimesters of pregnancy. MATERIALS AND METHODS: The transverse diameter of the atrium of the lateral vent ricle was prospectively measured in 739 consecutive antenatal ultrasou nd examinations by positioning electronic calipers on the luminal marg ins of the ventricular wall, perpendicular to the long axis of the ven tricle. RESULTS: The mean ventricular atrial diameter for the combined group of all 739 studies was 5.4 mm +/- 1.2 (standard deviation). The transverse diameter of the ventricular atrium did not progressively i ncrease with advancing gestational age. All fetuses younger than 17 me nstrual weeks had ventricular atrial diameters less than 8 mm. Four fe tuses had ventricular diameters of 10 mm br greater. CONCLUSION: A rea sonable upper limit of normal for transverse atrial diameter for gesta tional age of 25 weeks and above appears to be 10 mm. Prior to 25 week s, diameters over 8 mm are unusual in the healthy fetus and signal the need for a detailed evaluation of fetal anatomy.