Turner syndrome

In general, Turner syndrome is considered to be a sporadic condition.^[1] Recurrence in subsequent pregnancies is rare, but has occurred.^[2] It is assumed that the likelihood of recurrence is similar to that in the general population (in other words, no increased risk for couples who have had a previous affected pregnancy).^[3] To our knowledge, there also is no increased risk for other types of genetic abnormalities.

People who have had a previous fetus or infant with Turner syndrome may consider chromosome analysis in a subsequent pregnancy, for reassurance.^[1] The optimal time to determine risks and discuss prenatal testing is prior to pregnancy. People with questions about genetic testing and recurrence risks are strongly encouraged to speak with a genetic counselor or other genetics professional. 

While Turner syndrome is not common (about 1 in 2500 live female births), approximately 1 to 2% of all embryos have Turner syndrome - but 99% of these miscarry, usually during the first trimester.^[3] Turner syndrome may cause up to 10% of all first trimester miscarriages.^[2]

Women with Turner syndrome who conceive naturally have a 30% chance of having a fetus with chromosome abnormalities or congenital anomalies (birth defects) and should be offered prenatal testing. For affected women who conceive using egg donation, whether prenatal testing is recommended depends on the age of the egg donor.^[1]

Most cases of Turner syndrome are not inherited. Most commonly, Turner syndrome occurs due to a random event during the formation of an egg or sperm cell in a parent (prior to conception). For example, if an egg or sperm cell mistakenly loses a sex chromosome, and joins at conception with an egg or sperm containing an X chromosome, the resulting child will have a single X chromosome in each cell.

Mosaic Turner syndrome, occurring when a person has some cells with one X chromosome and some cells with two X chromosomes, is also not inherited. This also occurs due to a random event, during early fetal development rather than before conception.

In rare cases, Turner syndrome may be caused by a missing piece (partial deletion) of the X chromosome. A deletion can be inherited from a parent.^[4]

Genetic testing of an affected fetus or child can identify the type of Turner syndrome present and may help to estimate the risk of recurrence. People with questions about genetic testing or recurrence risks for Turner syndrome are encouraged to speak with a genetics professional. Please visit our page on how to find a genetic clinic.

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.