After adjusting for the years of infertility, infertility type, AMH, FET endometrial preparation protocol, number of transferred embryos, type of transferred embryos, and the number of intrauterine procedures, the frequencies of LBW were still higher in the RIF group compared to the control group (aOR 2.027; 95% CI: 1.025–4.009; P = 0.042). The gene discussed is AMH; the disease is Infertility.