Additional file 1: Supplementary Table 1. Excluded PIH subjects in the regression analysis, the increased risk of preterm birth and low birth weight was not present. We believe that it is related to the increased risk of PIH. Supplementary Table 2. Excluded PIH subjects in the regression analysis, the increased risk of preterm birth and low birth weight was not present in three groups. We believe that it is related to the increased risk of PIH. Supplementary Table 3. Excluding all women with PCOS/anovulation in the regression analysis, the risk of PIH (adjusted OR, 95% CI 4.62 [1.72–12.45]) was also increased in programmed FET group compared with the tNC-FET group in group C.