Fetal echocardiography. II. The diagnosis and significance of a pericardial effusion in the fetus using real-time--directed M-mode ultrasound.

By means of real-time--directed M-mode ultrasound, the hearts of normal and abnormal fetuses were evaluated for evidence of a pericardial effusion. Because of its limited potential space, the pericardial sac appears to become distended with fluid prior to ultrasound evidence of ascites, pleural effusions, or soft tissue edema. Fetal echocardiography, therefore, appears to be useful in the assessment of fetuses at risk for developing hydrops.