ACOG Position on First-Trimester Screening Methods
According to a Committee Opinion issued by The American College of Obstetricians and Gynecologists (ACOG), first-trimester screening for genetic defects is a real option for pregnant women, but only if certain criteria are met. New technologies, such as measuring nuchal translucency (NT), have allowed for earlier, noninvasive screening for chromosomal abnormalities. When combined with screening blood work in the first trimester, these methods have detection rates that are comparable to current standard second-trimester screening.
There are many advantages offered by screening in the first-trimester. When test results are negative, maternal anxiety may be reduced at an earlier point in the pregnancy. If positive, it allows women to take advantage of first-trimester prenatal diagnosis by chorionic villus sampling (CVS) at 10-12 weeks or second-trimester amniocentesis (15 weeks), as well as allow women to prepare for a child with health problems.
"Researchers developed this new method of testing because women want to know earlier in their pregnancies if there are any problems. Many women also want to avoid having an invasive diagnostic procedure such as CVS, which carries a small risk of miscarriage. However, it is important for women to recognize that a negative screen indicates that their risk of having a child with Down syndrome is reduced. This is not a diagnostic test," said Deborah A. Driscoll, MD, immediate past chair of ACOG's Committee on Genetics.
First-trimester screening can also help detect other chromosomal abnormalities such as trisomy 18. In addition, measurement of NT may help detect pregnancies at risk for major heart defects in the fetus. However, first-trimester screening cannot be used as a screening test for spina bifida.
"Women need to be aware of all the different screening options that are available, including their detection rates and limitations, so that they can choose the test that's best for them," said Dr. Driscoll.
For information about a recent study funded by the National Institute of Child Health and Human Development with regard to first-trimester screening, see DC Metro Area Medical Malpractice Law Blog, New Study Reports Effective First-Trimester Screening for Down Syndrome. For information regarding Down Syndrome, trisomy 18, spina bifida, and other chromosomal abnormalities, see the March of Dimes.