In some rare cases, spontaneous OHSS related with pregnancy has been described as depending on activating mutations of the FSH receptor (FSHR) gene, causing ovarian hyper-responsiveness to circulating FSH or even cross-responsiveness of FSHR to hormones having a structure similar to FSH, such as human chorionic gonadotrophin (hCG) or TSH [2,3]. This evidence concerns the gene FSHR and ovarian hyperstimulation syndrome.