The Sage™ prenatal screen is a non-invasive prenatal test (NIPT) for pregnant women which estimates the risk of a fetus having Down’s syndrome or other select genetic conditions. The Sage™ prenatal screen is an advanced screening test that is carried out on a small maternal blood sample. Pregnant women can expect test results from their healthcare providers within 3-5 working days from sample receipt.
How does it work?
During pregnancy, the placenta leaks fetal cell-free DNA (cfDNA) which circulates in the maternal bloodstream. As a result, a maternal blood sample contains a mixture of fetal and maternal circulating DNA. The Sage™ prenatal screen directly measures the amount of this cfDNA and can detect small changes in the DNA ratio between the maternal and fetal cfDNA to estimate the risk of a fetal chromosomal aneuploidy or a microdeletion being present.
What does Sage screen for?
Trisomies occur when three, instead of the usual two, copies of a chromosome are present in each cell. When the number of chromosomes differs from the usual two this is referred to as an aneuploidy. The Sage™ prenatal screen test estimates the risk of a fetus having Down’s syndrome (Trisomy 21), Edwards’ syndrome (Trisomy 18) and Patau’s syndrome (Trisomy 13). Edwards’ and Patau’s syndrome are much rarer than Down’s but are very serious and many affected babies are not born alive or do not survive for long after birth. Upon request, the Sage™ prenatal screen may also estimate the risk of other autosomal trisomies. The detection rate for Trisomy 21, 18 and 13 is greater than 99%.
Sex chromosome aneuploidies
In addition to the autosomal trisomies, the Sage™ prenatal screen may also report on sex chromosomal aneuploidies. Everyone also has a set of sex chromosomes in each of their cells. Women have two ‘X’ chromosomes (XX) while men have one ‘X’ and one ‘Y’ chromosome (XY). The impact of sex chromosome aneuploidy is generally much milder than aneuploidy of chromosomes 13, 18, and 21. The following aneuploidies can be screened for:
- Monosomy X – Turner syndrome
- XXX – Triple X syndrome
- XXY – Kleinfelter syndrome
- XYY – Jacob’s syndrome
Upon request, testing for select microdeletion syndromes is available. A microdeletion syndrome is caused by the absence of a small portion of genetic material in the chromosome. They vary greatly in severity, with the symptoms of microdeletions ranging from minimal developmental delays to severe anomalies e.g. cardiac defects, neurological malformations, etc.
Fetal sex determination
Upon request, and in regions where fetal sex determination is permitted, the fetal sex can be determined with 99.9% accuracy.