Why Oil-Based Hysterosalpingograms May Help Women Conceive

Peter Kovacs, MD, PhD


June 13, 2017

Oil-Based or Water-Based Contrast for Hysterosalpingography in Infertile Women

Dreyer K, van Rijswijk J, Mijatovic V, et al
N Engl J Med. 2017;376:2043-2052


A couple is considered infertile after unsuccessfully trying to get pregnant for a year or more.[1] Evaluation of tubal permeability is part of standard infertility evaluation.[1] To test tubal patency, a liquid has to be infused into the fallopian tubes, and various imaging techniques can check its permeability.[1] The "gold standard" is chromopertubation during laparoscopy. Laparoscopy also allows checking for further peritoneal or intra-abdominal pathology. It is, however, invasive and expensive. Contrast-enhanced imaging studies such as x-ray hysterosalpingogram (HSG) or sonohysterogram are simple and accurate outpatient diagnostic tests. They are mainly offered to patients at low risk for tubal disease.

HSG may even offer therapeutic benefits to those with otherwise unexplained infertility. It has been suggested that contrast liquids with different components may have a different impact on fertility, though not all studies agree on this.[2,3,4,5]

This large randomized controlled trial compared the impact of oil-based versus water-based contrast liquid on a woman's chance to conceive.

Study Summary

Over 1000 infertile women between the ages of 18 and 39 years from multiple clinics in The Netherlands were recruited. Eligible patients were randomly assigned to undergo HSG using oil-based or water-based contrast. Those who had evidence for tubal permeability were managed expectantly or underwent intrauterine insemination (IUI) treatment post HSG. Data based on 554 patients in each arm were included in the analysis.

Baseline parameters were comparable. A similar proportion of women were diagnosed with bilateral patency (86.1% vs 88.6%). A total of 58% and 57% of participants received expectant management, while 40% and 41% were treated with IUI. Approximately 2% of participants in both groups underwent in vitro fertilization (IVF). Only women whose male partner had adequate semen parameters for spontaneous conception were included in the study.

Here's what the researchers reported:

  • 40% of women in the oil-based group and 29% of those in the water-based group achieved an ongoing pregnancy during the follow-up period (odds ratio [OR], 1.37; 95% confidence interval [CI], 1.16-1.61; P<.001). The proportion of naturally, IUI-, or IVF-conceived pregnancies were similar.

  • 39% of women in the oil-based and 28% in the water-based contrast group achieved a live birth (OR, 1.38; 95% CI, 1.17-1.64; P<.001).


Testing tubal patency is an important step during infertility work-up. For those with expected pathology, laparoscopy should be offered. For those with no risk factors, HSG is typically the initial diagnostic test. An HSG can be done using x-ray or ultrasound as imaging, and various contrast liquids are available.

It has been long suspected that oil-based contrast offers extra benefits beyond its diagnostic value. It seems to enhance spontaneous conceptions. Various theories attempt to explain this finding. According to one explanation, the contrast may dislodge mucous plugs that have caused temporary obstruction. This benefit would be expected with both oil- and water-based contrast, though. Contrast is infused into the tubes through a catheter that is inserted into the uterus first. The catheter may injure the endometrium, which could enhance implantation, as has been suggested with endometrial injury in IVF-related studies.[6] This potential benefit would be similar with both types of contrast. The oil-based contrast may, however, have immunomodulatory effects that could support implantation.[7] This would be an added benefit over water-based contrast.

The choice of test is influenced by the potential side effects too. Oil-based contrast theoretically could get into the vasculature and may even cause embolism. It may result in granuloma formation in the peritoneal cavity.[8] It is also more likely to be associated with patient discomfort.

In cases when both contrast liquids are available, the use of oil-based contrast should be considered to improve subsequent spontaneous pregnancy rates. It is just as important to counsel patients who are found to have patent tubes to try spontaneously for 3-6 months after the intervention, as a good proportion of them will become pregnant without further help.



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