MORPHOMETRIC ANALYSIS OF THE GREAT-VESSELS IN EARLY FETAL LIFE

Pathological examination of the heart and great vessels was performed in 61 specimens obtained after surgical termination of pregnancy for p sychosocial indications at 9-18 weeks of gestation, The aorta and pulm onary trunk were identified and external diameters were measured at th e level of, and distal to the aortic valve and pulmonary valve, the le vel of the aortic isthmus and thoracic aorta, and the proximal and dis tal ductus arteriosus, All eight vessel diameters increased linearly w ith gestational age and the ratio of the diameter of the aortic isthmu s to that of the aortic valve or the distal ductus arteriosus also inc reased with gestation, Early pregnancy is characterized by rapid growt h of the fetal head and this may well be the consequence of a preferen tial distribution of left ventricular output in favour of the head due to relative narrowing of the aortic isthmus at this gestation.