If you’ve been struggling to get pregnant for some time, one of the first things a doctor may do is to check your Fallopian Tube Patency. This means = checking they are open and not blocked. The main form of this is a diagnostic test also known as HSG. Why do they do this? Well simply put, if your Fallopian Tubes are blocked by debris/mucus it’s not going to be helpful for a released egg to be fertilised and then to implant (1). However, can this diagnostic test actually help improve pregnancy rates in itself?! We take a look at some intriguing science around this….

So what is HSG? Why should I care? 

Hysterosalpingography (HSG) is a diagnostic test that is actually recommended in clinical guidelines when assessing fertility (1).  Essentially it is where your doctor will pass either a water based or oil based fluid (like a dye) under pressure through your Fallopian Tubes with imaging to see whether or not you have any blocks. However, there is some evidence that suggests that the procedure itself may actually increase pregnancy rates. 

Can the process of checking for blocks in Fallopian Tubes really enhance pregnancy rates on it’s own? 

This procedure has been around a long time. Over fifty years in fact. Initially, it was simply observed that there appeared to be a link between the procedure and women conceiving within six months. However, it has only been in recent years that there has been some proper research and meta-analyses (1, 2, 3) to really give this some evidence-based backing. 

Turns out, it appears to matter what type of solution is used: 

The majority of recent compelling data (including that covered in the Cochrane Review (1)) demonstrates that increased pregnancy rate occurs only after using an oil-based contrast medium. NOT when water-based medium is used (which is the alternative). (1, 2, 3). 

So it actually works?! 

There is indeed evidence that HSG or ‘tubal flushing’ using an oil based solution does appear to boost conception/live birth rates in some women. However, The benefit only appears to last for between three to six months following the procedure:

‘Tubal Flushing using oil based contrast medium probably increases short-term (six months) clinical pregnancy rates and may increase subsequent live-birth rate vs tubal flushing with water based contrast medium and no tubal flushing. But, it is not certain whether this effect persists beyond six months.’ (2) 

Do we know how/why it may work? 

The simple answer is no. However there are several possible theories as to why it may work:

The process itself may clear away small debris within the Fallopian Tubes: 

According to the Cochrane Review (1) there is increasing evidence that some cases of ‘blocked’ Fallopian Tubes may have been due simply to tubal plugs (or mucus). This may simply get dislodged by the oil based solution as it passes through under pressure. 

Does it work on more than just the Fallopian Tubes? 

Priming the Endometrium? It may work on more than just the Fallopian Tubes. This can either be as it alters the immunobiology of the Endometrium by altering the cytokine production (remember these are the body’s immune signals) click here for more. It may also play a role regulating and maturing the all important T cells. (3) These things together could prime the endometrium to be receptive to a fertilised egg. 

Can it even impact implantation? 

A study by Oxford University (3) looking at why oil based solutions may have better effects considered its role in implantation. The oil based contrast is typically derived from poppy seed oil, which contains opium alkaloids. Receptors for these opioids are present and seem to express themselves differently through the menstrual cycle. Appearing to peak around the time of implantation. 

‘Analysis suggests a role in implantation and could, at least in part, account for the aforementioned increase in pregnancy rates after the use of oil-based contrast’’. (3)

However, the exact mechanism behind increased rates of conception and Fallopian Tube HSG at this stage is not totally clear: 

The reality is these are all credible potential suggestions. However, at this stage we are not quite sure the exact reason why it may contribute to increased pregnancy rates for some women. 

Is the process of checking or unblocking Fallopian Tubes painful? 

This is something very much worth considering. The answer is that yes, for some women it can be very painful. One study indicated that up to 40% of women may experience moderate to severe pain (3). For others it is just uncomfortable. Interestingly enough though, Oxford University considered whether or not more pain equated to improved effectiveness. Their conclusion? Yes.  

Seems in this case pain may well indeed equal gain! 

The study (3) demonstrated that greater pain with the oil-based solution ‘significantly increased the ongoing pregnancy rate from 30% to almost 50% as compared to the use of water contrast.’ 

The theory behind why this may be the case is that in the presence of greater blockages, the pressure will be higher and therefore more painful. However, as the solution passes through this debris and mucus can be cleared out. Hence the improved rates of conception. (3)

So, what to do? 

As usual it is not super clear cut. It is also very individual and of course it is a discussion to have with your doctor. The reality is, if you have been struggling to get pregnant your doctor will likely check your tubes using HSG. The bonus shown by recent research is that even the practise of doing this as a means of diagnosis can potentially boost chances of conception (1-3). The downside is that it may be uncomfortable. 

What about tubal flushing without the imaging part? 

Essentially this is the HSG but without the imaging part to see what is going on. It is typically an elective process and will be done privately. The idea of course is that it could boost pregnancy rates for the aforementioned reasons. Some doctors are more willing than others to do this and it may not be cheap and pain free. However, once again there is evidence (1-3) that for some women this can enhance fertility up to six months following the procedure. 

Who should be particularly cautious? 

The oil-based solution does contain Iodine. Given the Thyroid’s sensitivity to this, anyone with Thyroid issues should have a very careful and considered discussion with their doctor before considering this treatment. (2). 

Conclusion: is it worth investigating or ‘flushing’ the Fallopian Tubes? 

Whilst we still don’t fully understand the mechanism of how this diagnostic test works on fertility. There is certainly evidence that in some women it can enhance fertility and increase live birth rates up to six months following the procedure. However, as usual it is not a slam dunk. It is also a normal part of the process when a doctor is investigating your fertility. The upside is that it appears the investigation could help your chances! As always though, this is food for thought for a full discussion with your doctor. Good luck! 

References: 

1) Mohiyiddeen L, Hardiman A: Tubal Flushing for subfertility: The Cochrane Database of Systematic Reviews: 2015 May: 2015 (5)

2) Wang R, Welie NV, Rijswijk JV: Effectiveness on fertility outcome of tubal flushing with different contrast media: systematic review and network meta-analysis: Ultrasound Obstetric Gynecology: 2019; 54: 172-181  

3) Weile N, Dreyer K, Mol BWJ: Treatment effect of oil-based contrast is related to experienced pain at HSG: a post-hoc analysis of the randomised H2Oil Study: Human Reproduction (Oxford, England): 2019 Dec; 34(12):2391-2398

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