ABSTRACT Key Content Unexplained infertility accounts for up to 30% of cases of infertility. Potential causes for unexplained infertility have been proposed including reduced oocyte quality, poor endometrial receptivity, ovulatory PCOS, subclinical endometriosis and low semen quality. Investigations for the diagnosis of infertility include assessment of ovulation, tubal patency, semen quality and uterine structure. Predictive models such as the Hunault model can predict the likelihood of natural conception in those with unexplained infertility and can help guide management options which include expectant management, intrauterine insemination (IUI) (with or without ovarian stimulation) or in vitro fertilisation (IVF). Current NICE guidance advises that couples with unexplained infertility are referred for IVF after 2 years of trying to conceive naturally. The recent ESHRE guidance supports IUI as a first‐line treatment for those with unexplained infertility. There is some evidence that both IUI and IVF confer a benefit in those with a poor prognosis to natural conception; however, further good‐quality research is required. Learning Objectives To review current definitions and potential hypotheses for the causes of unexplained infertility. To summarise the best practice for the investigation of the subfertile couple. To summarise and review recent evidence on the treatment of unexplained infertility.
Raperport et al. (2026) studied this question.