Trisomy 13, also known as Patau syndrome and trisomy D, is the third most common fetal aneuploidy, after trisomy 21 (Down syndrome) and trisomy 18. Trisomy 13 is the condition of having three copies, rather than two, of chromosome 13. Trisomy 13 can be full, mosaic, or partial. Trisomy 13 has an approximate incidence rate of 1 in 5,000 births.
The risk of trisomy 13 can be assessed in the first and second trimesters via ultrasound and maternal serum screenings. A diagnosis can be made through fetal karyotype tests like amniocentesis or chorionic villus sampling (CVS).
Trisomy 13 often presents as a collection of abnormalities affecting multiple areas of the body, including, but not limited to, cleft lip, cleft palate, congenital heart defects like atrial septal defect (ASD) and ventricular septal defect (VSD), kidney issues, eye issues, decreased muscle tone, extra fingers and/or toes, and brain or skeleton abnormalities.
Trisomy 13 has a high rate of miscarriage. Trisomy 13 is almost always fatal in the perinatal period, with nearly 80% of babies dying before one month of life. The median life expectancy for a baby born with trisomy 13 is 7 to 10 days. The babies who do survive passed the first month of life have medical complications like difficulty feeding and breathing, reflux, slow growth, seizures, high blood pressure, and severe developmental delays.
The reoccurrence risk for full trisomy 13 is 1% or the maternal age-related risk, whichever is greater. Parental genetic testing is recommended prior to a subsequent pregnancy.