Turner Syndrome, also called 45, X or monosomy X, is the most common chromosomal abnormality that exclusively affects females. Turner syndrome is the condition of missing all or part of the X chromosome in all or part of a female’s cells. Turner syndrome can be full, mosaic, or partial, with an estimated 50% of all cases being full, 30% to 40% of cases having mosaicism, and 10% to 20% being partial due to a structural abnormality of one X chromosome.
Turner syndrome is estimated to affect 3% of all female babies conceived; however, only 1% of these babies survive to delivery. The incidence rate of Turner syndrome is 1 in 2,500 female live births. The risk of Turner syndrome can be assessed in the first and second trimester via ultrasound and maternal serum screenings. A diagnosis can be made through fetal karyotype tests like amniocentesis or chorionic villus sampling (CVS).
Turner syndrome is associated with other fetal anomalies such as cystic hygroma, hydrops fetalis, polyhydramnios, short femurs, and congenital heart defects like hypoplastic left heart syndrome. 30% to 60% of cases have an associated renal (kidney) anomaly.
Turner syndrome is highly fatal, with a 98% to 99% rate of miscarriage; however, the condition is not universally fatal. 1% of females diagnosed with Turner syndrome will survive pregnancy and have a normal lifespan; however, long-term survivors have varying complications ranging from vision and hearing issues, stunted growth, thyroid conditions, infertility, learning disabilities, and developmental delay.
Turner syndrome typically occurs as a sporadic condition, and the recurrence risk is not associated with maternal age-related risk. Parental genetic counseling is recommended prior to subsequent pregnancies.