Stratified analysis
Results of stratified analysis were shown in Table S1-3 . The associations of history of HA-treated IUAs with adverse obstetric outcomes were generally similar across different subgroups of maternal age (confidence intervals of subgroups overlap) (Table S1 ). Similarly, mode of conception (Table S2 ) and maternal parity (Table S3 ) also did not modify the associations of history of HA-treated IUAs with adverse obstetric outcomes