A population-based study of prevalence of Down syndrome in Southern Thailand.

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Population-Based Study of Prevalence of Cleft Lip/Palate in Southern Thailand.

INTRODUCTION: Oral cleft is a common craniofacial birth defect that leads to long-lasting adverse outcomes. In Thailand, there have been two studies of the prevalence of oral clefts using data from university hospitals during 1969 through 1978 and 1988 through 1999, which found prevalence rates of 1.23 and 1.22 per 1000 live births, respectively. OBJECTIVE: The primary outcome was to assess the prevalence of oral clefts from the birth defects registry during 2009 through 2013 in three provinces in southern Thailand. The secondary outcomes were to correlate the risk of oral cleft and maternal age. DESIGN: Population-based study. SETTING: Four hundred sixty-seven hospitals in three provinces in southern Thailand. PARTICIPANTS: Oral cleft cases and maternal data-including live births, stillbirths, and termination of pregnancy following a prenatal diagnosis-were collected from the birth defects registry. RESULTS: Of the total 186,393 births, there were 269 oral cleft cases, giving an average prevalence of 1.44 per 1000 births (95% CI, 1.22-1.63). The most common cleft type was cleft lip and palate (45.0%), followed by cleft palate (29.0%), with 15.6% syndromic cleft. The mean maternal age was 28.0 ± 6.4 years. There were no differences in prevalence of oral clefts among the different maternal age groups. However, advanced maternal age 35+ years was associated with syndromic cleft children. CONCLUSIONS: The prevalence of oral clefts was 1.44 per 1000 live births, with 15% of cases having an associated congenital anomaly or a recognized syndrome. Increased maternal age was associated with a higher prevalence of syndromic cleft.

Prevalence of neural tube defect in southern Thailand: a population-based survey during 2009-2012.

BACKGROUND: Neural tube defects (NTDs) are a group of congenital malformation of the central nervous system that leads to permanent physical disability and requires lifelong treatment. In Thailand, there have been three published articles on NTDs, all hospital-based studies, which found prevalence of NTDs of 4.8-6.7 per 10,000 live births. OBJECTIVE: It was our purpose with this study to determine the prevalence and type of NTDs in southern Thailand through a population-based survey. METHOD: Data were obtained through the population-based surveillance during 2009-2012 in three provinces (Songkhla, Phatthalung, Trang) in southern Thailand. Entries in the birth defects registry included all live births, all stillbirths after 24-week gestational age, and termination of pregnancy following the prenatal diagnosis at any gestational age of all congenital anomalies. RESULTS: During 2009-2012, 148,759 births were registered in the three provinces. Twenty-eight NTD cases were identified, giving an average of 1.88 per 10,000 births (95 % CI 1.20-2.51): 12 cases with anencephaly (42.8 %), 5 with occipital encephalocele (17.9 %), and 11 with myelomeningocele (39.3 %). The birth prevalence per 10,000 births of anencephaly, encephalocele, and myelomeningocele were 0.81, 0.33, and 0.74, respectively. Sixteen (57 %) were detected in live births, and 12 (43 %) were detected by prenatal diagnosis which later resulted in termination of pregnancy. CONCLUSIONS: The prevalence of NTDs based on the population-based study in southern Thailand was low. About 40 % of NTD cases were detected prenatally and later terminated. Hence, examining only registry live births will result in an inaccurately low NTD prevalence rate.