Variation tendency and influence factors of sex ratio at birth in Shanghai,2004-2013

Objective To explore variation tendency and influence factors of sex ratio at birth in Shanghai and to provide basic data for family planning.Methods Birth registry data from 2004 to 2013 in Shanghai municipality were collected and the characteristics of sex ratio at birth was described.With contribution rate in economics,we calculated contributions of various factors to the increase of sex ratio at birth.Multivariate logistic regression model was adopted to evaluate influence factors of sex ratio at birth.Results Sex ratio at birth for immigrant population in Shanghai reduced from 125 in 2004 to 117 in 2013 and was expected to reach to the normal level in 2025.The increased sex ratio at birth was mainly due to the immigrant populations.The increase of parity (odds ratioOR_{2 vs.1}=1.19,OR_{3 vs.1}=1.67,OR_{>3 vs.1}=1.61)and low education level of the mother (OR=1.01)were influencing factors of the increased sex ratio at birth.The elder age of the parents may related to the decreased sex ratio at birth (OR_father=0.99 and OR_mother=0.99).Conclusion Immigrant population in Shanghai showed a high sex ratio at birth.Low education level of mother and gender preference of parents have influence on sex ratio at birth.