TGFB1 and spontaneous abortion: Four polymorphic loci that may be associated with miscarriage were screened by Pubmed, clinvar, omim, China Knowledge Network, and Wanfang databases, namely TNF-α gene -308G/A locus (rs1800629); TGF-β1 gene c.328C/T locus (rs1555755242); TGF-β1 gene c.133C/T locus (rs1555755308); TNFRSF4 gene c.193C/T locus (rs587777075).