How long does the fertility-enhancing effect of hysterosalpingography with oil-based contrast last?

Nienke van Welie, Kimmy Rosielle, Kim Dreyer, Joukje van Rijswijk, Cornelis B. Lambalk, Nan van Geloven, Velja Mijatovic, Ben Willem J. Mol, Rik van Eekelen, on behalf of the H2Oil Study Group

Research output: Contribution to journalArticleResearchpeer-review


Research question: Does the fertility-enhancing effect of tubal flushing during hysterosalpingography (HSG) with oil-based contrast change over time? Design: This was a secondary analysis of the H2Oil (long-term follow-up) study, a multicentre randomized controlled trial evaluating the effectiveness of oil-based and water-based contrast during HSG. The main outcome was ongoing pregnancy. Cox proportional hazards models for time to ongoing pregnancy were fitted over 3 years of follow-up. Results: Data on 1107 couples were available; 550 couples had oil-based contrast and 557 water-based contrast at HSG. Ongoing pregnancy rates after 3 years were 77% and 71%, respectively. Median follow-up was 9–10 months (5th—95th percentile: <1 to 36). The hazard ratio for ongoing pregnancy for oil versus water over 3 years of follow-up was 1.26 (95% confidence interval [CI] 1.10–1.45). The scaled Schoenfeld residual plots showed a decrease in hazard ratio that was linear with log-transformed time. After including an interaction with log-transformed time, the hazard ratio immediately after HSG was 1.71 (95% CI 1.27–2.31) and reduced to no effect (hazard ratio of 1) at approximately 2 years. There was no evidence for a change in hazard ratio over time in a subgroup of women who experienced pain during HSG. Conclusions: The hazard ratio for ongoing pregnancy of oil-based versus water-based contrast was 1.71 immediately after HSG, gradually decreasing and plateauing towards a hazard ratio of 1 (indicating no effect) after approximately 2 years. This supports the hypothesis that oil-based contrast might dislodge debris or mucus plugs from the Fallopian tubes, but this has yet to be definitively proved.

Original languageEnglish
Pages (from-to)1038-1044
Number of pages7
JournalReproductive BioMedicine Online
Issue number6
Publication statusPublished - Dec 2020


  • Female infertility
  • Hysterosalpingography
  • Oil-based contrast medium
  • Ongoing pregnancy
  • Water-based contrast medium

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