Neurodevelopmental outcomes of school-age children conceived after hysterosalpingography with oil-based or water-based iodinated contrast: long-term follow-up of a nationwide randomized controlled trial

Abstract STUDY QUESTION Does preconceptional exposure to oil-based iodinated contrast media during hysterosalpingography (HSG) impact children’s neurodevelopment compared with exposure to water-based alternatives? SUMMARY ANSWER Our study found no large-sized effects for neurodevelopment in children with preconceptional exposure to oil-based iodinated contrast media during HSG compared with water-based alternatives. WHAT IS KNOWN ALREADY HSG is widely used as a diagnostic tool in the female fertility work-up. Tubal flushing with oil-based iodinated contrast has been shown to enhance fertility outcomes in couples with unexplained infertility, increasing the chances of pregnancy and live birth compared with water-based alternatives. However, oil-based contrast contains higher doses of iodine and has a longer half-life, and concerns exist that iodinated contrast media can affect women’s iodine status and cause temporary (sub)clinical hypothyroidism in mothers and/or foetuses. Considering that thyroid hormones are vital to embryonal and foetal brain development, oil-based contrast media use could increase the risk of impaired neurodevelopment in children conceived shortly after HSG. Here we examine neurodevelopmental outcomes in school-aged children conceived after HSG. STUDY DESIGN, SIZE, DURATION This is a long-term follow-up of the H2Oil trial in which oil-based or water-based contrast was used during HSG (Netherlands; 2012–2014; NTR3270). Of 369 children born