Our randomised controlled trial (RCT) found that a hysterosalpingogram (HSG) with the oil‐soluble contrast medium (OSCM) lipiodol improves pregnancy rates amongst couples with unexplained and endometriosis‐related infertility. These results were supported by the findings of our observational study of the first 100 women to undergo the procedure after it was offered as an innovative treatment in New Zealand from September 2003.

To further assess the safety and efficacy of lipiodol procedures and present together the complete data set of the procedures performed in our RCT and those performed as innovative procedures (n = 296) prior to it being offered as a standard fertility treatment.

Women with infertility underwent a therapeutic lipiodol procedure by HSG technique with fluoroscopy X‐ray screening. Primary outcomes were clinical pregnancy within six months of the procedure and live birth.

The overall pregnancy rate for the 296 women was 40.2%. The live birth/ongoing pregnancy rate was 31.4%. The pregnancy rates for women under the age of 40 with endometriosis and unexplained infertility were 51.1 and 31.4%, respectively.

Lipiodol can now be considered a standard treatment for both unexplained and endometriosis‐related infertility. The precise mechanism behind the fertility‐enhancing effect of lipiodol has yet to be elucidated. This study supports a mechanism of effect on the endometrium with possible enhanced receptivity of the endometrium to embryo implantation.