Endometriosis and Miscarriage

I’ve been hearing a lot in the news recently about endometriosis and miscarriage. I’ve seen reports on various news websites, which I won’t link to here because I noticed most of them are strewn with errors, the best summary is here on the endometriosis.org website.

I shan’t repeat what has already been written about the research too much, but I will try to add a few points that I think are worth addressing. Firstly, endometriosis and miscarriage (or any pregnancy complication for that matter) are serious problems and if one exacerbates the other that is cause for more attention to be paid to both. Given the fact that women with endometriosis can struggle to become pregnant, it is therefore extremely important for potential parents and medical professionals to know how best to care for pregnant women with endo if they are in a high risk group for any complications. 

To very quickly re-iterate the study’s findings; a group assessing the medical records of 5,375 women with confirmed endo and 8,280 women without endo between 1981 and 2010 from a database of records from all the state hospitals in Scotland found that the women with endo had a 76% increased risk of miscarriage. This is where I would like to make my first point. Hardly any of the reports on news sites make clear what that actually means, a 76% increase from what? It turns out miscarriages are more common than I thought and most occur during the very, very early stages of pregnancy. They may even occur before the woman even knows she’s pregnant. Of those women that do progress into pregnancy, depending on who you ask, the risk of miscarriage is around 1 in 6 to 1 in 5, which equates to 17-20%. So what does the 76% increase for women with endo actually mean?  It means the risk of miscarriage for women with endo rises to 30-35%. For anyone who wants to see the math (and I’m sure you do *sarcasm*) it goes like this 

There was also a noted increase in the risk of ectopic pregnancy in women with endo, a  2.7 times greater risk to be precise. The rate of ectopic pregnancies is much smaller than miscarriage, around 1 in 100. For women with endo then, this would increase the risk of ectopic pregnancy to around 3 in 100, a seemingly small, but nonetheless important, increase. 

This isn’t the first large study into adverse pregnancy outcomes in women with endometriosis which drew a similar conclusion. A study published in 2014 from Denmark analysed the records of 24,667 women with endo compared to 98.668 from endo-free women between 1977-2009. This study found the risk of miscarriage in women with endo rose to 24%, or around 1 in 4 women. This study also raised a good point regarding adverse pregnancy outcomes and the method of conception. Because of the subfertility experienced by women with endo, they are far more likely to undergo assisted reproductive therapy (ART) like in-vitro fertilisation (IVF). A study reviewing all current research on this topic was published in January this year and concluded that, for women with stage I-II endo undergoing ART the miscarriage rates were the same as the for endo-free women,  for women with stage III-IV though there was a lower rate of live births.

A deeper analysis is needed of the current data to really pull out some specific clinically relevant information. For example, as we have just seen, there may be a difference in pregnancy outcomes for women with different stages of endometriosis. Another issue to clarify would be does any specific hormonal therapy prior to conception have any effect on the outcomes. 

It would seem then that the evidence available certainly suggests that endometriosis is associated with an increase in adverse pregnancy outcomes. This information is most needed in the hands of obstetricians and midwives who can carefully monitor pregnant women with endo and react quickly to any warning signs that may endanger the life of the mother or child. 

A big question that remains then is why do women with endo have this increased risk? It is not simply enough to pay extra attention to pregnant women with endo, we need to know what causes the problems in the first place and how to correct them. Several studies, including my own research, have found that the endometrium in women with endo differs from that of endo-free women in several ways. Being as the endometrium is the point of contact for the developing embryo and its receptivity essentially dictates the embryo’s fate, more investigation is needed into endometrial alterations. Some studies have noted changes in the immune cells of the endometrium of women with endo, which may result in poor initial attachment of the embryo to the endometrium. This may then result in a decrease in viability of the developing foetus resulting in an increased risk of pregnancy loss. Further study is needed to discover how the endometrium of women with endo differs from endo-free women, how these differences affect the function of the endometrium and how this may be corrected.