| Objective: To understand the following information of children aged0～5in Chongqing: the overall prevalence of birth defects, the main kindsof birth defects and their ranks, and the distribution characteristics ofpopulation, area and period. To explore the environmental chemicalelements related to birth defects; to provide a scientific basis for theprevention of birth defects.Methods:1. Subjects selection for baseline investigation of birth defects:multi-stage stratified cluster and mixed sampling was used. Chongqing wasdistricted to one-hour economic circle, northeast wing and southeast wingaccording to the economic development strategy. We selected a randomsample of16districts/counties from the first stage according to theproportion in each level. We chose one street and two towns from eachdistrict/county in the second stage, and simple random sampling was used.In the third stage, we enrolled two villages/neighborhoods from eachtown/street, and also simple random sampling was used. Finally, the totalnumber of investigated areas was96. We enrolled all resident children,born during Oct1,2004(0o’clock)~Sep30,2009(24o’clock)(0~5yearsold) and living in the investigated areas exceeding3months.2. Survey methods of birth defects: Investigators included techniciansthat were engaged in the diagnosis of birth defects for a long time andservice workers in birth control. Subjects went through physicalexamination and were asked of disease history by our staff during May to September,2004.3. Diagnostic criteria of birth defects: Except for congenitalmalformations of the body surface, other birth defects must be diagnosedby county or above county level hospitals. Expert consultation must be heldif county hospitals couldn’t give the diagnosis. Children were registeredwith a final diagnose of birth defects.4. Defination of sample points in ecological study: the data of thechemical elements contents were measured by cooperating with GeologicalProspecting Bureau in Chongqing. Therefore, the sample points werevillages/neighborhood that been selected both in population-basedinvestigation of birh defects and the data provided by GeologicalProspecting Bureau. Finally, the total number of sample points was57.5. The collection of soil samples and determination of chemicalelement contents: according to the specifications of multi-targetgeochemical survey from China Geological Survey Bureau, the basic gridsurface soil sample for collection were1km2.. One soil sample wascollected from each grid with a sample depth of0~20cm, and a weight1kg.All samples were collected by stainless steel shovel, preserved in specialsampling bags, and records were well made. After pretreatment, sampleswere detected by ICP-MS for the contents of the following11chemicalelements: copper, zinc, iodine, selenium, lead, arsenic, cadmium, chromium,mercury, nickel, fluoride.6. Statistical analysis: database was established by EpiData3.02. SAS9.0was used in the data analysis. P value less than0.05was considered tobe statistically significant. Statistical approaches included descriptiveanalysis, chi-square test, rank correlation test, Shapiro-wilk test and K-Wrank sum test. Results:1. The baseline survey results of birth defects:(1) overall prevalenceof birth defects: The total number of investigated subjects was9784, amongwhich371were cases with birth defects. The prevalence of birth defectswas37.92‰.(2) types of defects: There were38types of birth defects. Thetop5were hernia, cryptorchidism, polydactylia, congenital heart diseaseand funnel chest.(3) the gender distribution of birth defects: Theprevalence of birth defects in boys was58.26‰, while14.67‰in girls.The boys had a higher incidence than girls (χ~2=126.81, P<0.05).(4) theage distribution of birth defects: The age group0~,1~,2~,3~, and4~5years old had a prevalence of birth defects37.69‰,49.76‰,38.79‰,32.55‰,33.96‰, respectively. And the difference between groups was notstatistically significant (χ~2=9.22, P>0.05).(5) the prevalence of birthdefects in the three regions: southeast wing, northeast wing and one-houreconomic circle had an prevalence of birth defects39.84‰,49.48‰,33.48‰, respectively. And the difference was not statistically significant(χ~2=11.75, P＜0.05).(6) the distribution of birth defects in urban and ruralareas: The prevalence of birth defects in rural areas (44.88‰) was higherthan that of urban areas (28.36‰)(χ~2=18.19, P＜0.05).(7) the prevalenceof birth defects in districts/counties: Qijiang county had the highestprevalence while Chongshou district had the lowest prevalence among the16selected districts/counties. The prevalence of the16areas wasstatistically different (χ~2=34.63, P<0.05).2. The results of ecological study:(1) rank correlation: The incidenceof the defects was negatively correlated with chemical elements contents(copper, chromium and iodine) in the soil. The correlation coefficients were-0.333、-0.296、-0.39, respectively (P<0.05).(2) the K-W rank sum test:high incidence area and low incidence area was differentiated by the50thquantile (P50) of the birth defects of the survey points. The results showed a significant difference in the content of copper, chromium and iodine inthe two area (P<0.05).Conclusions1. The overall birth defects prevalence of children aged0～5inChongqing was37.92‰. There were38types of birth defects. The top5were hernia, cryptorchidism, polydactylia, congenital heart disease andfunnel chest. The results also showed that the occurrence of birth defects inboys was higher that girls, rural areas than urban areas. And there was nodifference among age groups. The general trend of birth defects inChongqing: the incidence is higher in areas far away from downtown thanin areas not far away.2. Hospital-based birth defects monitoring had been widely applied，Population-based birth defects monitoring should be strengthened atpresent. Then combined the two parts of the monitoring data, to establishan efficient hospital-based combined population-based of birth defectsmonitoring system, comprehensive discovered the real level of birth defects.Reducing its prevalence and improving the quality of the population3. The results of rank correlation and rank sum test suggested that, theoccurrence of birth defects may be related to the low level contents ofcopper, chromium and iodine in the soil. |
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