HealthPartners - Your guide to pregnancy

FETAL ANATOMY SCAN Many health care providers use a fetal anatomy scan to look for physical signs that the baby has an obvious birth defect. This is usually done between 18 and 22 weeks of pregnancy. It’s sometimes called a Level II ultrasound. If a specific problem is found, your health care provider or a genetic counselor can help you understand what that means. An ultrasound cannot detect all birth defects.

DIAGNOSTIC TESTS If a genetic screening test comes back positive or your health care provider needs more detailed information, you may be offered one of the following diagnostic tests: • Chorionic Villus Sampling (CVS) – Uses a tiny tissue sample taken from the placenta. It is done during the first trimester, usually 10-13 weeks. Its main purpose is to see if the baby has a normal number of chromosomes (46). It can be done earlier in the pregnancy and provides a diagnosis more quickly than amniocentesis. The risk of miscarriage from the test is very low.

• Amniocentesis – Tests fluid taken from the amniotic sac surrounding the baby. When the test is done depends on the reason for it. Testing amniotic fluid confirms whether the baby has a normal number of chromosomes (46). Fluid for genetic testing and neural tube issues is usually collected between 16 and 18 weeks. Testing for fetal maturity and blood incompatibility problems is usually done much later. Amniocentesis is considered 99.5% safe, but it is not a routine test. It is only done to detect a highly probable medical problem.

Your Guide to A Healthy Pregnancy 13