In the linked study (doi: 10.1136/bmj.a716), Bhattacharya and colleagues assess the effects of clomifene citrate or intrauterine insemination compared with expectant management in couples with unexplained infertility.1

One in seven couples trying to have a child fails to conceive after one year of regular unprotected intercourse.2 Basic fertility investigations including semen analysis, confirmation of ovulation, and tubal patency testing using hysterosalpingography find no specific cause of infertility in about a third of these couples, who are given a “diagnosis” of unexplained infertility.3 Underlying mechanisms could include cervical, uterine, ovulatory, peritoneal, immunological, or fertilisation defects. Therefore, the true prevalence of this diagnosis will depend on the range of investigations available at individual centres and the willingness of infertile couples to undergo extensive testing. In addition, the multiple causes of unexplained infertility create considerable difficulty in planning targeted treatment.

The treatment of unexplained infertility is generally …