Sex Ratio At Birth In 13 Counties/cities Of China, 1993-2005

Objective: The first objective is to describe the epidemiological characteristics of sex ratio at birth(SRB); the second objective is to determine if the SRB was abnormally high and if the secular trends of SRB was increasing; the third objective is to analyze the factors associate with the high SRB in China from 1993 to 2005.Methods: The data was obtained from the perinatal health care surveillance system of China-U.S. Collaborative Project on Birth Defects and Disability Prevention. According to the UNITED NATIONS, the SRB was calculated as the number of live male births to 100 live female births. According to the two conditions that the number of live births variated little yearly and surveillance system coverage was more than 90 percent, we chose 13 counties/cities as research fields including 9 counties/cities in Jiangsu and Zhejiang province in south during Jan 1, 1993 to Dec 31, 2005 and 4 counties/cities in Hebei province in north during Jan 1, 1993 to Dec 31, 2000. The research population was new born who had a valid gender record. X2 test were used in comparation of rate or proportion, multivariable Logistic linear regressions were used to control the confounders. Statistical analysis was performed using the SPSS10.0 package,α=0.05.Results: (1) During Jan 1, 1993 to Dec 31, 2005, 612 393 live births including 319 368 male newborns and 293 025 female newborns in these areas. The SRB was 107.91 in South from Jan 1, 1993 to Dec 31, 2005 and 110.37 in North from Jan 1, 1993 to Dec 31, 2000. (2) The SRB did not change with the mothers'age, educational levels, occupation and ethnicity. The SRB was not different between urban (109.22) and rural (108.98), but it was higher in the North (110.37) than that in the South (108.70). Among 13 counties/cities, the SRB in Pinghu county was the lowest (106.08) and in Fenghua county was the highest (115.23), both of two counties were in Zhejiang province. (3)The SRB increased significantly in South from 1993 to 2005. However in North, the SRB declined from 1993 to 1996 and increased from 1997 to 2000. (4) The results of multivariate analysis showed that the high parity associated with the high SRB.Conclusion: The SRB was higher than 107 in 13 counties/cities indeed in south and north areas in China, and it increased from 1993 through 2005, but it was not as serious as the census reports during the same period. The SRB did not change with the mothers'age, educational levels, occupation and ethnicity, the high SRB was mainly associated with the high parity.