In most cases pyelectasis resolves normally, having no ill effects on the baby.
It was thought to be a marker for obstruction, but in most cases it resolves spontaneously.
There is some discussion about what degree of pyelectasis is considered severe enough to warrant further investigation and most authorities use 6mm as the cut-off point.
This, along with other factors such as age and abnormal maternal serum screening (exa, Integrated or Quad screen), may be grounds for a prenatal diagnostic test such as an amniocentesis to rule out Down syndrome.
Babies with unresolved pyelectasis may experience urological problems requiring surgery.