Morphometric analysis of early fetal great vessels shows linear growth with gestational age and suggests relative narrowing of the aortic isthmus may preferentially direct left ventricular output to the rapidly growing fetal head.
Normative fetal great vessel diameters may refine early echocardiography; leaves open prospective validation before clinical adoption.
Pathological examination of the heart and great vessels was performed in 61 specimens obtained after surgical termination of pregnancy for psychosocial indications at 9-18 weeks of gestation. The aorta and pulmonary trunk were identified and external diameters were measured at the level of, and distal to the aortic valve and pulmonary valve, the level of the aortic isthmus and thoracic aorta, and the proximal and distal ductus arteriosus. All eight vessel diameters increased linearly with gestational age and the ratio of the diameter of the aortic isthmus to that of the aortic valve or the distal ductus arteriosus also increased with gestation. Early pregnancy is characterized by rapid growth of the fetal head and this may well be the consequence of a preferential distribution of left ventricular output in favour of the head due to relative narrowing of the aortic isthmus at this gestation.
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Hyett et al. (1995) studied this question.
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