The genetics counselor will review your history and your family history to determine your risk of certain disorders. If an increased risk is identified, the counselor will then discuss with you the options available regarding non-invasive genetic screening (such as NIPT) and/or invasive genetic testing (such as amniocentesis or CVS). It should be noted that the choice of whether to have any of these screening or diagnostic tests performed is completely up to you. Our intent is to help provide you with the most helpful and useful information to make informed decisions regarding the management of your pregnancy.
The most common conditions for which a patient may be offered genetic counseling and/or genetic testing would include the following:
- The patient will be 35 years old or older at the time of delivery (Of note: the American Congress of Ob/Gyn guidelines now specify that all patients should be offered genetic screening and/or genetic testing at any age)
- A structural fetal abnormality is diagnosed at the time of an ultrasound
- The patient has family history of genetic disorders
- The patient has a “positive” (abnormal) NIPT screen or a “positive” (abnormal) 2nd trimester AFP screen through the California State Prenatal Screening program
- The patient has a positive screening test for a genetically related disorder (such as cystic fibrosis).
- The patient has had a prior child with a genetic abnormality
- The patient has a desire, for one reason or another, to know for certain the genetic composition of the baby (even if the screening tests are otherwise normal)
During an amniocentesis, a small amount of amniotic fluid is removed from the sac surrounding the baby and tested. The sample of fluid (less than one ounce) is removed through a very thin needle inserted into the uterus through the abdomen, and the fluid is replaced naturally within 24 hours. The procedure is performed using ultrasound guidance so that the exact position of the needle may be followed throughout the procedure. The fluid is then sent to a laboratory for analysis.
Different tests can be performed on a sample of amniotic fluid, depending on the genetic risk and indication for the test. Any patient may undergo amniocentesis if they so desire, but this procedure is generally only performed under very specific circumstances. The procedure is ideally performed between 16-18 weeks’ gestation (though it may be performed any time after 15 weeks’ gestation and later in the pregnancy in certain circumstances). The risk of miscarriage following an amniocentesis varies in different studies. In our experience, the risk of complications is less than 1 in 2000 procedures given our ultrasound-guided technique and experience. Most patients tell us that the procedure is less uncomfortable than they anticipated, and the level of discomfort is comparable to what you might expect when having your blood drawn.