Down syndrome testing

Down syndrome is when the fetus has one additional chromosome: # 21. Its occurrence is mostly related to advancing maternal age. At age 30 the rate is about 1 in 1000 and at age 40 the rate is about 1 in 100. Many women chose to screen for Down_s syndrome. There are non-invasive tests and more invasive ones. The non-invasive ones include the nuchal translucency ultrasound (NT test) which is usually done at about 11 to 14 weeks gestation and is usually done along with a blood test. A second set of blood tests done at 15 to 20 weeks gestation will be also done. The results of these above tests are combined and give you a probability of your baby having Down syndrome. Based on this final number you should decide if you want to have an amniocentesis or not. Most women do the non-invasive tests initially and only do the invasive ones if the results are not reassuring. The invasive tests include the Choroid Villus Sampling (CVS) which is done at the end of your first trimester (11 to 13 weeks) and the Amniocentesis which is done at beginning of your second trimester (16 to 20 weeks).Timing of the above tests vary depending upon where you live. Do talk to your health care provider about the options you have as well as the timing of the tests.