Immediate and delayed effects of oligohydramnios on limb development in the rat: chronology and specificity.

Experimental oligohydramnios has been induced in pregnant rats on the 15th gestational day. Characteristic features of the amniocentesis syndrome can be observed in the posterior limbs and tail early after the amniotic puncture. Histological studies of the affected limb buds reveal immediate endothelial rupture of the marginal vein in the interdigital areas. General and nonspecific effects of the syndrome appear after 30 minutes: venous congestion, blebs, and periendothelial oedema. Such vascular disturbances can be either reversible or lethal. Proper regulation of the haemorrhagic effects does not occur. Growth and differentiation of the condensed digital rays are often unimpaired. Since the condensed preskeletal rudiments are spared by the haemorrhage, resorption of the hematoma results in limb defects which may be limited to the soft tissues. The haemorrhagic sites are selectively dependent on the vascular pattern of the developing limb at the time of experiment. Current hypotheses formulated to explain the amniocentesis syndrome are reviewed on the basis of the new descriptive data. Congenital constriction band syndrome and amniotic ruptures have been observed in rare cases.