© 2018, Genassist, Inc.

By Keith S. Wexler, MBA, Maternal Fetal Medicine, Prenatal Diagnosis and Biotech/Life Sciences Consultant, GENASSIST, Inc.

Paul Wexler, M.D., F.A.C.O.G., Medical Director, GENASSIST, Inc.

Clinical Professor, Department of OB/GYN, University of Colorado Health Sciences Center

Clinical Professor, Division of Genetics/Dept. of Pediatrics, Univ. of Colorado/The Children’s Hospital

The breakdown of fetal cells in the maternal circulation make it possible for laboratories to screen for Fetal DNA during pregnancy. When fetal cells break down cell free DNA (cf DNA) is released. It is possible to duplicate many copies of this DNA so that testing is possible.

This prenatal non-invasive testing can be performed as early as the 10th week of pregnancy. 

Trisomy 9 is characterized by three copies of chromosome #9 instead of the expected two copies.  Complete or partial Trisomy 9 usually ends in a miscarriage, but rarely may continue to term.

Chromosomal abnormalities of chromosome #9 are particularly important since partial trisomy of chromosome #9 involving either the short arm (p arm) or the long arm (q arm) does occur, can continue to term and may not have a shortened life span e.g. Trisomy 9p.

Trisomy 9 can present as having all cells with three copies of chromosome #9 or be present in combination with a normal karyotype (mosaic). There are often facial and skull findings including small head (microcephaly), low set ears and moderate to severe developmental delay.

*Trisomy 9 is not available on all Maternal Fetal DNA Panels.

http://www.trisomy9.org/

If a Maternal Fetal DNA test result comes back as “High Risk” for a chromosomal abnormality, the recommendation (1) is to confirm the diagnosis by amniocentesis.

Ultrasound performed in pregnancy after 15 weeks gestation can help identify some babies with Trisomy 9.

(1)The American College of Obstetricians & Gynecologists, Committee Opinion Number 545 December 2012, The American College of Obstetricians and Gynecologists Committee on Genetics, The Society For Maternal-Fetal Medicine Publications Committee, “NonInvasive Prenatal Testing for Fetal Aneuploidy”.