Pattern of Turner syndrome in Singapore (1999-2004)

Turner syndrome is the most common sex chromosomal abnormality in female foetuses, and is associated with a high proportion of cardiac anomalies. The aim of this study was to look at the incidence, demographical data and epidemiological pattern of Turner syndrome in Singapore from 1999 to 2004 and to examine the birth defects associated with this condition, specifically with reference to cardiac defects.

Data on Turner syndrome cases born in 1999-2004 were retrieved from the National Birth Defects Registry (NBDR) and analysed. Data on congenital cardiac defect cases notified to the NBDR in the same time period were also retrieved and compared with the Turner syndrome cases.

There were a total of 101 cases of Turner syndrome in the six-year period from 1999-2004, yielding an overall incidence of 0.85 per 1,000 female live births, or one in 1,180 female live births. The incidence was lowest among Indians (0.38 per 1,000) compared to Malays (0.72 per 1,000) and Chinese (0.90 per 1,000). 75 cases (74.3 percent) had the 45,X karyotype, while the other 26 cases (25.7 percent) were mosaics. The mean maternal age for 45,X was lower (32.2 years, range 22-42) compared to mosaics (34.5 years, range 27-40). 19.8 percent (20/101) were live births, 38.6 percent (39/101) were terminated pregnancies and 41.6 percent (42/101) were spontaneous miscarriages. 13.9 percent of Turner syndrome babies had cardiac defects compared to 1.2 percent in the general population (p-value is less than 0.0001). Major cardiac defects found among Turner syndrome babies compared to the general population included the coarctation of the aorta (5.9 percent compared to 0.03 percent, p-value is less than 0.0001), atrial septal defects (3.0 percent compared to 0.6 percent, p-value is 0.006), a hypoplastic left heart (2.0 percent compared to 0.05 percent, p-value is less than 0.0001), aortic hypoplasia (3.0 percent compared to 0.01 percent, p-value is less than 0.0001) and dextrocardia (1.0 percent compared to 0.02 percent, p-value is 0.0002).

Cardiac defects, particularly left-sided ones, are significantly more common among Turner syndrome foetuses. The true incidence of this syndrome is likely to be higher than that quoted in this study, and can only be solved when a complete screening of an entire population has been performed.