Vascular pathogenesis of transverse limb reduction defects.

Evaluation of four patients with unilateral transverse limb reduction defects indicates that some instances of this structural defect may be the result of an in utero vascular accident. Three of the four patients had microscopic evidence of fetal vascular occlusive disease on multiple sections of the placenta, suggesting that occlusion of the brachial artery was secondary to embolization from the placental vascular thrombi. The fourth, a 116 mm crown-rump long fetus, had a massive thrombus occluding the brachial artery, which was felt secondary to hypovolemia and hypoperfusion associated with fetal blood loss during placental abruption. Recognition of the disruptive vascular pathogenesis of some cases of unilateral transverse limb reduction defects explains their negligible recurrence risk. In such cases attention should be focused on careful gross and, microscopic evaluation of the placenta.