A population-based study of prevalence of Down syndrome in Southern Thailand
Down syndrome (DS) is the most common chromosomal disorder that causes mental retardation. In 2009, a population-based birth defects study was implemented in three provinces in southern Thailand. This study aimed to determine the prevalence of DS in the studied regions, and the proportion of DS fetuses detected by prenatal screening.
Data were obtained from a population-based surveillance study undertaken during 2009-2013. Entries in the birth defects registry included live births, stillbirths after 24 weeks gestational age, and terminations of pregnancy following prenatal diagnosis. Infants with clinical characteristics of DS had a chromosomal study to make a definite diagnosis.
Of the total 186 393 births recorded during the study period, 226 DS cases were listed, giving a prevalence of 1.21 per 1000 births [95% confidence interval (CI) 1.05-1.37]. The median maternal age was 36.5 years with a percentage of maternal age ≥35 years of 60.6%. Seventy-seven cases (34.1% of all cases) were diagnosed prenatally and these pregnancies were terminated. The prevalence of DS per 1000 births was significantly higher in older women, from 0.47 (95% CI 0.28-0.67) in mothers aged <30 years to 0.88 (95% CI 0.59-1.17) in mothers 30-<35 years (P<0.01), and to 4.74 (95% CI 3.95-5.53) in mothers ≥35 years (P<0.001).
The prevalence of DS significantly increased with maternal age. About 35% of DS cases were detected prenatally and later terminated. Hence, examining only registry live births will result in an inaccurate prevalence rate of DS.
Key wordsbirth defect registry Down syndrome prenatal screening termination of pregnancy trisomy 21
Unable to display preview. Download preview PDF.
This research was supported by the Birth Defects Association (Thailand) and the Thai Health Promotion Foundation. The authors gratefully thank the staff of the 466 hospitals for their assistance with data collection. The authors thank Mr. David Patterson from the International Affairs Office in the Faculty of Medicine, Prince of Songkla University, for editorial help.
- 1.Boyd PA, Khoshnood B, Loane M, Garne E, Dolk H, and the EUROCAT working group. Survey of prenatal screening in Europe for structural malformations and chromosome anomalies, and their impact on detection and termination rates for neural tube defects and Down’s syndrome. BJOG 2008;115:689–696.CrossRefPubMedPubMedCentralGoogle Scholar
- 3.Savva GM, Walker K, Morris JK. The maternal age-specific live birth prevalence of trisomies 13 and 18 compared to trisomy 21 (Down syndrome). Prenat Diag 2009;30:57–64.Google Scholar
- 12.Dissaneevate S, Jaruratanasirikul S, Chanvitan P, Janjindamai W. Congenital malformations of newborns at Songklanagarind Hospital. Songkla Med J 2003;21:267–276.Google Scholar
- 16.Statistical Forecasting Bureau, National Statistical Office, Ministry of Information and Communication Technology, Thailand. Key Statistics of Thailand 2012. [internet]. Available from http://service.nso.go.th/nso/nsopublish/pubs/pubsfiles/Key55_T.pdf (accessed September 14, 2014).Google Scholar
- 24.Lai FM, Woo BH, Tan KH, Huang J, Lee ST, Yan TB, et al. Birth prevalence of Down syndrome in Singapore from 1993 to 1998. Singapore Med J 2002.43:70–76.Google Scholar
- 26.Lau TK, Cheung SW, Lo PS, Pursley AN, Chan MK, Jiang F, et al. Non-invasive prenatal testing for fetal chromosomal abnormalities by low-coverage whole genome sequencing of maternal plasma DNA: review of 1982 consecutive cases in a single center. Ultrasound Obstet Gynecol 2014;43:254–264.CrossRefPubMedGoogle Scholar