Oil- versus water-based contrast media for hysterosalpingography (HSG) in infertile women with unevaluated indications: a randomized controlled trial (H2Oil-2 study)
When couples find it hard to get pregnant, doctors often carry out a special X-ray test called a hysterosalpingography (HSG) to check if the fallopian tubes are open. During this test, a small amount of liquid dye is gently passed into the womb and tubes. Doctors currently use two types of dye: one made with water and one made with oil. Early evidence suggests that oil-based dye might slightly increase the chances of getting pregnant naturally, but more evidence is needed. This trial compares both dyes in women aged 18 and older. Half of the women will receive the water-based dye, and the other half will receive the oil-based dye. Researchers will follow up with participants for at least six months to see which dye leads to more successful, healthy pregnancies and live births, while also checking mother and baby health.
At a glance
What is this study about?
For many women, finding out why it is difficult to conceive can be stressful. A common first step is a test called a hysterosalpingography (HSG). This is a specialised X-ray examination where a doctor gently injects a liquid dye through the cervix into the womb and fallopian tubes. This dye shows up clearly on X-rays, allowing doctors to spot any blockages or unusual shapes that might prevent an egg from meeting sperm.
At the moment, hospitals use two main kinds of contrast dye for this test: water-based dye and oil-based dye. Both are approved and safe to use. Interestingly, previous research has suggested that flushing the fallopian tubes with an oil-based dye might actually help clear minor debris and boost a woman's chance of conceiving naturally. However, doctors need more reliable proof before recommending one dye over the other for everyday care.
The H2Oil-2 clinical trial aims to settle this question. Participants are randomly allocated to receive either the oil-based dye or the water-based dye during their planned HSG. The main goal is to see which group has a higher rate of successful pregnancies resulting in a healthy live birth within six months of the procedure.
The researchers are also keeping a close eye on safety and overall health. They will track how quickly women get pregnant, monitor any side effects from the procedure, and check thyroid hormone levels in both mothers and newborn babies, as the iodine in the dye can sometimes temporarily affect the thyroid gland.
Key takeaways
- The study compares water-based and oil-based dyes used during routine HSG fertility X-rays.
- The main aim is to find out which dye leads to more live births within six months.
- Participation involves your scheduled HSG test, blood tests for thyroid health, and regular follow-up checks.
- Both dyes are already routinely used in hospitals and considered safe.
- Taking part is voluntary and does not stop you from having future fertility treatments like IVF.
Who may be eligible?
This study is open to adult women aged 18 and over who are currently experiencing difficulties getting pregnant and are already scheduled to have an HSG test as part of their fertility investigations.
Because the study focuses on general fertility checks, it is meant for women who need an HSG to investigate their fallopian tubes and womb, before moving on to more intensive treatments like IVF.
Your clinical team will check whether you have any specific allergies to X-ray dye or active pelvic infections that might make having an HSG unsuitable at this time. If you are pregnant or suspect you might be, you cannot take part.
Could this study suit you?
Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.
- I am a woman aged 18 or older.
- I am having difficulty getting pregnant.
- I am already planning to have an HSG dye test to check my fallopian tubes.
- I do not have an active pelvic infection.
- I am not known to be allergic to contrast dye or iodine.
What does participation involve?
If you choose to join the study, you will have your standard HSG test at the hospital. A computer system will randomly choose whether your test uses the water-based or oil-based dye; neither you nor your doctor will choose. After the test, you will be asked to report any symptoms or side effects, such as pain or bleeding.
You will have a simple blood test before the procedure and another about one month later to monitor your thyroid gland. Over the next six months, the study team will stay in touch to see if you have become pregnant naturally or started fertility treatments such as IUI or IVF. If you do become pregnant, the team will follow your progress through to the birth of your baby, where your baby's standard newborn heel-prick test will also check their thyroid levels. In total, participation lasts from the day of your test until around six months later, or until after your baby is born.
Potential risks and benefits
Locations (1)
- —UnverifiedNetherlands
Common questions
What is an HSG test?
An HSG is an X-ray test where dye is placed into the womb to check if your fallopian tubes are clear and healthy.
Can I choose which dye I receive?
No. A computer randomly decides which dye you get so the trial remains fair and scientifically accurate.
Does having this test guarantee I will get pregnant?
No. While some evidence suggests the dye might help clear the tubes, it does not guarantee pregnancy.
Why are thyroid levels checked?
Both dyes contain iodine, which can occasionally affect how the thyroid gland works. Simple tests check that your levels remain normal.
What happens if I decide to leave the trial?
You can leave at any point. Your normal NHS care and fertility treatments will continue as usual without any disadvantage.
How to find out more
Always speak to your GP or specialist before deciding to take part in a study.
Interested in taking part?
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