My patient’s NIPT is positive for XXX (triple X syndrome). What does this mean?
Your patient’s NIPT result suggests the presence of an extra copy of the X sex chromosome. NIPT is a screening test; false positives, though rare, can occur. The actual chance for the pregnancy to have XXX syndrome depends on many factors, including the patient’s clinical and family history.
Next steps to consider: You should discuss the results and the potential clinical implications with your patient. The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine state, “All women with a positive cell-free DNA test result should have further detailed counseling and testing and should have a diagnostic procedure before any irreversible action is taken.” Confirmation prior to birth can also help with pregnancy and neonatal management.
What is XXX syndrome?
XXX syndrome is a condition that is caused by a female having an extra copy of the X sex chromosome (three copies of the X chromosome instead of the usual two copies).
What are the features of XXX syndrome?
XXX syndrome is likely to result in livebirth. XXX syndrome is usually not associated with intellectual disability or severe birth defects. Some of the common features of XXX syndrome include delayed speech and motor development. Females with XXX syndrome can be taller than average height. Pubertal development and fertility are usually normal.
What is the prevalence of this condition?
Approximately 1 in 1000 females are born with XXX syndrome. This condition usually happens by chance and can be associated with advanced maternal age.
What testing should be considered?
- Specialized genetic tests such as karyotyping, fluorescence in situ hybridization (FISH), qPCR, and microarray are available to confirm the presence of XXX syndrome.
- These confirmatory tests are generally performed on cells from chorionic villus sampling (CVS) or amniocentesis during pregnancy, on cord blood or peripheral blood sample after the baby is born, or on products of conception (POC) in the case of miscarriage.
- Ultrasound evaluation may be useful in aiding with prenatal diagnosis, but a normal ultrasound cannot exclude this condition. Ultrasound is usually normal with XXX.