The aetiology of infertility is thought to include disordered inflammatory factors such as irregular prostaglandin (PG, particularly PGE2 and PGF2α) and cyclooxygenase 2 (COX-2) production [40], abnormal ER- and PR-mediated signalling pathways associated with progesterone resistance [41], impaired trophoblast invasiveness, and uterine contractility [42]. This evidence concerns the gene PTGS2 and Infertility.