Strengths and limitations
This is the first large-scale, multi-province, retrospective cohort study that investigated prevalence of postpartum contraception, unintended pregnancy and induced abortion nationwide in China. The study manifests several limitations. Our study relied on women’s retrospective reporting of their postpartum contraception, pregnancy, and abortion; and hence may be subject to recall bias. We recorded the timing with respect to initiation of postpartum contraception, resumption of sexual intercourse, pregnancy, and abortion by rounding the number of months; and this may not have provided adequate accuracy in measuring cumulative rates.