Percutaneous umbilical blood sampling (PUBS)

Percutaneous umbilical blood sampling (PUBS), also called cordocentesis, is a fairly new test that is done on the fetus. The test has improved the diagnosis and treatment of Rh-incompatibility and other blood disorders. The advantage of the test is that results can be available within a few days. The disadvantage is it carries a slightly higher risk of miscarriage than amniocentesis does.

How the Test Is Performed
Guided by ultrasound, a fine needle is inserted through the mother's abdomen into a tiny vein in the umbilical cord of the fetus. A small sample of the baby's blood is removed for analysis. Blood disorders, infections and Rh-incompatibility are detectable with PUBS.
If the fetus is found to be Rh-positive and its mother is Rh-negative, doctors have time to give it a blood transfusion, if necessary. This procedure can help prevent life-threatening anemia that can develop if the mother is isoimmunized (she has antibodies that attack her baby's blood).

NEW TESTS TO HELP PREDICT PROBLEMS
There are new tests available that can help your doctor learn about fetal problems. A new urine test holds promise as a prenatal predictor of Down syndrome. Urine is examined for hyperglycosylated HCG (HHCG); when combined with ultrasound measurements, the results have proved to be valuable in detecting the problem. At this time, the test is not available commercially.

You may have heard about another test that combines a detailed ultrasound, a blood test and the mother-to-be's age to gauge a woman's risk of having a baby with Down syndrome. The test is called nuchal translucency screening; however, it is not widely available. There are no known risk factors, but the results depend on the accuracy of the ultrasound test.

Other new prenatal genetic tests are being used in some areas.
These tests for the following conditions.
Familial Mediterranean fever-This disease is found in people of Armenian, Arabic, Turkish and Sephardic Jewish background. Prenatal testing helps identify carriers of the recessive gene so diagnosis can be made quickly in a newborn to avoid a potentially fatal medical problem.
Canavan's disease-Most commonly found in people of Ashkenazi Jewish background, Canavan's disease screening can be combined with Tay-Sachs screening to determine if a fetus is affected.
Congenital Deafness caused by the connexin-26 gene-If a couple has a family history of inherited deafness, this test may identify the problem before birth. By identifying the problem before birth, measures can be taken to manage the problem immediately.