Relationship of fetal hydronephrosis to spinal dysraphism.

Thirty-one fetuses with hydronephrosis and 14 fetuses with spinal dysraphism were sonographically examined. In only one instance was spinal dysraphism associated with hydronephrosis. This single case was identified in a term pregnancy. There was no statistically significant association of urinary tract dilation and open spinal defects in utero. This observation tends to confirm the reports that urinary tract dilatation associated with spinal dysraphism is less frequent when neonates and children are compared. the progressive decrease in this association appears to extend to the fetal period.