Pregnancy First Trimester Screening

The first trimester screen is a combination of blood work drawn from you and ultrasound images of your baby. These results combined with risk factors determined by your age, ethnicity and medical history provide you with a set of information that determines your risk of abnormalities with your baby. It's important for you to know that the first trimester screen does produce 5 percent false positive results--meaning that 5 percent of the time abnormal results are reported and are then dismissed after further testing is done. This test is not intended to diagnose abnormalities it is merely a test to determine your risk and what additional testing should be done.

The first trimester screen is an optional screening that looks for chromosomal abnormalities including Down Syndrome Trisomy-21 and Trisomy-18. The nuchal translucency--the fluid beneath the skin on the neck of the fetus--has been found to be associated chromosomal abnormalities, as are abnormally high levels of the hormones hCG and PAAP-A that are present in pregnancy. Risk of some cardiac disorders can be determined with the first trimester screen as well. This screen does not look for risk factors of neural tube disorders.

The New England Journal of Medicine published a study in November of 2005 declaring the first trimester screen the most accurate and non-invasive screening test available to you.

The first trimester screen can be confused with the second trimester screenings done between weeks 15 and 20. These tests are often referred to as the quad screen or the triple screen. Neither of these tests is as accurate as the first trimester screen.

There are no risks to you or your baby in the performing of these tests. Other than discomfort from having your blood drawn, there are no known side effects.