OBJECTIVETo describe and analyze epidemiological characteristics of babies with neural tube defects (NTD) by sex and birth outcome in a high-prevalence and a low-prevalence areas of China.METHODSBirth defects surveillance data collected from 1992 through 1994, as a part of the Sino-American cooperative project on NTD prevention, were used to classify NTD as four categories, i.e., anencephaly, encephalocele, high-level and low-level spina bifida according to the sites of lesion (high vs. low level lesion were cervicothoracic and lumbosacral, respectively). Each category was sub-classified, according to single or compound defect, as isolated external defects (including those with NTD only) or multiple external defects (including those with NTD and another major external birth defects that is not the sequence of a defect such as cleft lip with or without cleft palate). The rates of anencephalus, encephalocele, high- and low-level spina bifida (SB) in males and females and their sex ratios were calculated, adjusted for urban and rural areas, season, category and birth outcome by sex and sites of lesions (high vs. low).RESULTSTotally, 784 NTD cases were identified from 326 874 recorded births (including live births, stillbirths and fetal deaths with a gestation age of at least 20 weeks). The prevalence rates of anencephalus (1.30 per 1 000 female births) and high-level SB (3.99) in females were higher than those (0.66 and 1.66 per 1 000 male births) in males in the high-prevalence northern regions; with adjusted prevalence rates of females 1.8 - 2.1 times greater than those of males. In the low-prevalence southern regions, the prevalence of high- (0.32 per 1 000 female births) and low-level SB (0.21) in female were higher than those in males, with high- and low-level SB rate of 0.10 and 0.09 per 1 000 male births), with adjusted rates for females of 1.3 - 1.6 times higher than in males. Isolated NTD accounted for more than 80% of all NTD cases, and the prevalence of isolated NTD in females (2.57) was higher than that in males (1.40).CONCLUSIONSThe sex differences in NTD existed between north and south, in accordance with the phenotype of NTD. It suggested that proportion of high level SB and anencephalus in females could increase as the prevalence of NTD going up, anencephaly, high- and low-level SB had the different genetic and environmental background.

OBJECTIVE:To describe the epidemiology of neural tube defects (NTDs) in high- and low-prevalence areas of China.METHODS:Birth defects surveillance data, collected from 1992 through 1994 was analyzed. These data were collected as part of the Sino-American cooperative project on NTDs prevention. We classified NTDs as anencephaly, encephalocele, high-level and low-level spina bifida (SB) according to location of the lesion (high vs low) and whether the defect was isolated or occurred in association with other birth defects. Rates were compared in the high-prevalence (North) region and the low-prevalence (South) region, after adjusted for classification, urban and rural, season and sex, and calculated the adjusted rate of NTDs.RESULTS:Among seven hundred and eighty-four NTDs cases in 326 874 recorded births (include in livebirth, stillbirth and fetal death with a gestational age of at least 20 weeks), the overall NTDs prevalence in the North was 5.57/1,000 births, and in the South was 0.88/1 000. There were also significant differences in the prevalence of anencephaly, encephalocele, high-level and low-level SB between North (0.97, 0.49, 2.75 and 1.11/1,000 birth) and South (0.36, 0.15, 0.21 and 0.14/1,000 birth) (P < 0.01), with adjusted prevalences in the North 3 - 7 times higher than those in the South. There were significant difference between urban (2.04) and rural areas (6.57/1,000 birth) in the North (P < 0.01), urban (0.52) and rural areas (0.95/1,000 birth) in the South (P < 0.05). Adjusted prevalence rates in the rural were 3 - 4 times higher than those of urban in the North and 1.6 - 1.9 times higher than in the South; The seasonal rate of high-level SB increased between September and November in the North (3.44/1,000 birth), while the seasonal rate of anencephaly decreased between September and November (0.18/1,000 birth) in the South. However there were no seasonal changes in other classified NTDs both in the South and North.CONCLUSIONS:The birth prevalence of NTDs in the North of China was the highest in the world. There were significant differences between the North and the South, urban and rural. There was seasonal change in high-level SB in the North, which was in accordance to the phenotype of NTDs. It was suggested that there might exist etiological heterogeneity among anecephalus, low- and high-level SB.

Objective To describe the epidemiological characteristics of oral clefts in 5 counties of Hebei Province of China, between 1993 and 1996. Methods Detailed data were obtained through the Birth Defects Surveillance System that was established in 1992. The study population comprised the total live and stillbirths (with a gestational age of at least 20 weeks) in the counties between 1993 and 1996. Birth prevalence of oral clefts (including cleft palate alone, cleft lip+ /-cleft palate) was calculated for specific birth populations. Results In the period of 1993-1996, the overall prevalence of oral clefts was 2. 080 total births, and the rates of cleft palate and cleft lip +/-cleft palate were 0. 300 and 1. 780 , respectively. The highest rate (3. 350 ) of oral clefts was seen in Yuanshi county, and the lowest (1. 660 )in Xianghe county. the highest birth prevalence (2. 700 ) of oral clefts was in the year 1993, and the lowest (1. 680 ) in 1995. There was no significant seasonal variation of oral clefts. The overall male/female ratio was 1. 38 : 1. The birth prevalence rates of cleft lip +/-cleft palate for male and female were 2. 080 and 1. 430 respectively (X2=4.14,P0. 05). Conclusion The birth prevalence of oral clefts in the 5 counties of Hebei Province was persistently high, and sex differences existed during the period of between 1993 and 1996. Possible environmental factors and indicated and differences in susceptibility exist between two sexes.