Pyelectasis - Prenatal Genetics

Urinary tract dilation or pyelectasis is a collection of fluid in the fetal kidneys causing them to dilate. This is seen in approximately 1-2% of pregnancies, and is more common in male than in female fetuses. In the majority of cases, the fluid in the kidneys drains and does not have an impact on the baby's health. 

Pyelectasis and Down Syndrome Risk

Pyelectasis is considered an ultrasound "soft marker," which increases the chance that the baby may have Down syndrome. Although Down syndrome can occur in any pregnancy, the chance for Down syndrome increases with the mother's age. When pyelectasis is seen on ultrasound, the risk for Down syndrome is approximately one and one-half (1.5) times a woman's age-related risk. 

If the urinary tract dilation is isolated, prenatal cell-free DNA screening (NIPS) is recommended if not yet performed. If the screening is reassuring (negative), no further diagnostic testing is recommended. Prenatal diagnostic testing by amniocentesis is, however, always available for any indication, to test for chromosome abnormalities during pregnancy. 

Genetic counseling to review the implications of the EIF is available. 

Pyelectasis and Other Health Risks

Babies with pyelectasis have an increased risk for urologic problems that may require surgery after birth if the collection of fluid in the kidneys increases throughout pregnancy. If the pyelectasis persists, an ultrasound of the newborn kidneys is recommended. Typically, however, pyelectasis disappears by the third trimester of pregnancy or in the first year of life, and has no negative effect on the baby.