Differences in the incidence and characteristics of BDs between singleton and multiple births
A total of 53,196 births between 2012 and 2018 that were associated with BDs were included in the analysis, of which 49,872 were singletons and 3,324 were multiple births (Table 1). The mean incidence of BD for multiple births was 109.99 per 1,000 births, which was significantly higher than that for singleton births (26.29 per 1,000 births; χ2=7600, P <0.001). Significant differences were also found between singleton and multiple births associated with BDs with respect to mean maternal age, the distribution of maternal age group, maternal domicile, maternal education, maternal parity, and infant sex (all P <0.05). Compared with women who had singletons with BDs, those who had multiple pregnancies associated with BDs were more likely to be older, live in an urban environment, have a college-level education or above, and be multiparous.