Statement about aspirin
Due to the lack of consensus in using LDA for twin pregnancies, the two centers participated in this study carried out different policies on aspirin use for twin pregnancies and thus made this observational study feasible. Given that the specification of aspirin tablets in China is either 25mg or 100mg, and ACOG recommendation for pregnant women is 81mg daily, therefore, 100mg/d was prescribed to participants to avoid under dosage.