Effect of interpregnancy interval of childbearing aged women on birth weight of single live birth neonates

Objective To understand the effect of interpregnancy interval (IPI) of childbearing aged women on the birth weight of single live birth neonates in Shaanxi province. Methods A questionnaire survey was conducted among the childbearing aged women selected through multistage stratified random sampling in Shaanxi during 20l0-2013, all the childbearing aged women had definite pregnancy outcomes. The interpregnancy interval of the childbearing aged women and the birth weight of the newborns were used as the independent variables and dependent variables respectively in multiple linear regression model and quantile regression model, and confounding factors were controlled. Results A total of 13 063 women at childbearing age and their infants were investigated. The incidence of low birth weight and macrosomia was 3.54% and 7.62% respectively. Multiple linear regression analysis showed that there was no significant difference in birth weight among different IPI group and control group. Quantile regression analysis showed when birth weight was at 5 percentiles, the difference in birth weight between newborns whose mothers had short interpregnancy interval (<12 months) and those in control group was significant, when the birth weight was ≥90 percentiles, the birth weights of newborns whose mothers had long interpregnancy interval (60-119 months) were higher than those in control group, the difference was significant. As the increase of the percentiles of birth weight, the extent of changes gradually increased. Conclusion The analysis indicated that both short (<12 months) and long (60-119 months) interpregnancy interval would had negative effects on birth weights of newborns. Therefore, planning for pregnancy is important for having a good perinatal outcome. Key words: Birth weight; Interpregnancy interval; Quantile regression