birth defect
8.Inguinal hernia,undescended testicle,congenital mental retardation were usually not included for statistical analysis on birth defect. Excluding these birth defects,the prevalence of birth defects in study areas was 537.2 per 10 000 births and the first five main birth defects were anencephaly, congenital heart diseases,spina bifida,hydrocephaly(40.5 per 10 000 births)and encephalocele(31.2 per 10 000 births).

