1.1 Database search
We searched PubMed and Embase library to identify the works of literature reporting the relationship between BW and the risk of any adult-onset cancers published before March 2021. The following keywords were used for retrieval: (“Birth weight” OR “Birth size”) AND (“Cancer” OR “tumor” OR “brain cancer” OR “breast cancer” OR “bladder cancer” OR “colorectal cancer” OR “endometrial cancer” OR “esophageal cancer” OR “kidney cancer” OR “lung cancer” OR “leukemia” OR “lymphoma” OR “liver cancer” OR “nervous system tumors” OR “malignant melanoma” OR “osteosarcoma” OR “ovarian cancer” OR “prostate cancer” OR “testicular cancer”). The detailed search strategy was shown in Table S1. Then we add studies included in systematic reviews and meta-analyses and duplicate articles were excluded.