It is common for mothers to want to know as much as possible about their developing babies. Discovering your child’s genetic health and chromosomal status, for example, could give you information about certain conditions your child may have. This can help you make informed decisions about your child’s future. You can learn about your baby’s genetic health in the first two trimesters of pregnancy through a test called serum screening. Here’s what to expect from serum screening for Down syndrome.
What Is Serum Screening?
Serum screening, also called the multiple marker test, uses a maternal blood sample in the second trimester of pregnancy to assess the risk of chromosome disorders in the infant. A serum screening has the ability to detect Down syndrome and Edwards syndrome, as well as conditions such as anencephaly and spina bifida. This noninvasive test for Down syndrome works by analyzing the mother’s DNA fragments during pregnancy. Analyzing cell-free DNA sequences can determine whether the infant has more chromosome 21 present than the average baby. This leads to an accurate prediction of whether the fetus has Down syndrome.
During maternal serum screening, the mother gets a single blood test done around 15 to 21 weeks’ gestation. If the mother already received first trimester screening, she may only receive serum screening in the second trimester for open neural tube defects. Serum screening measures biochemical markers in the mother’s blood, including alpha feto-proteins and inhibin A. the levels of these markers are typically different in mothers carrying babies with Down syndrome. Measurable differences, therefore, could point to a chromosomal abnormality.
Serum screening does not provide a definitive Down syndrome diagnosis. Instead, it simply groups mothers into high or low-risk categories based on predictions. Your healthcare provider should receive the results of your serum screening within one week of the blood test. This type of noninvasive prenatal DNA testing is popular in mothers who may have risk factors for Down syndrome, such as advanced maternal age. If the chance for Down syndrome is greater than 1/385 according to the serum screening, it is a positive result. False positive results are possible.
Are There Other Down Syndrome Screening Options?
Mothers have several noninvasive prenatal tests (NIPT) to choose from when trying to screen for Down syndrome and other chromosomal abnormalities, on top of serum screening. The NIPT test you choose depends on your unique needs, concerns, and goals. Here is a breakdown of three noninvasive screening options available to mothers in the second trimester:
MaterniT ® 21 PLUS. This NIPT test screens for Down syndrome and trisomy 21, as well as other conditions, such as DiGeorge syndrome. Parents can customize their tests according to risk factors.
MaterniT® GENOME. This test is a robust option that can give parents information about every chromosome for a more comprehensive view of the baby’s health.
informaSeq®. This tests for common trisomies such as Down syndrome but has the option not to reveal information about fetal gender, unlike other NIPT tests.
Serum screening has been in use for over 40 years. Only recently, however, noninvasive prenatal screens became available. Serum screening can detect 80-90% of infants with Down syndrome, trisomy 18, and open neural tube defects depending on the test chosen and the stage of pregnancy. Later, a diagnostic test can confirm or deny a positive serum screen. First and second trimester serum screening may be the right NIPT for your family.