Both have benefits. CVSis done earlier, which means (hopefully) putting your worries to rest sooner, or alternatively, an earlier termination or more time to plan and prepare for your child’s condition. CVS results also come back quicker than amnio’s. It may be difficult to find an experienced provider to do the test, though, because fewer doctors perform CVS than amnio. But, if you’re at particular risk for neural tube defects, amnio is the clear choice — CVS won’t detect these. Amnio also allows you to postpone making your decision (to test, or not to test) until after you’ve seen the results of your second trimester screenings.
American College of Obstetrics and Gynecologists. Your pregnancy and birth. 4th ed. Washington, DC: ACOG; 2005.