Today on Science & Sensibility, regular contributor Henci Goer takes a look at a new retrospective study looking at the potential relationship between cesarean birth and endometriosis development in the mother in the years after her surgery. Did you know that research indicates an increase in endometriosis for those women who have undergone a cesarean delivery? Henci shares this new study and asks us to continue to look further. - Sharon Muza, Community Manager, Science & Sensibility.

'© Patti Ramos Photography

My very first post in Science & Sensibility back in 2009 was a round-up of case studies and series reporting on the formation of endometriosis - also called "endometrioma" because the cells formed a solid mass - in the cesarean wound. I commented that case studies could serve to draw attention to possible serious complications worthy of further investigation and ended the post with the hope that researchers would take a closer look at this one. Now I have run across a study that does exactly that. I wanted to share it with you today.

Swedish investigators, Andolf, Thorsell, and Kallen (2010), used a national in-patient data registry linked to a birth registry to identify all women giving birth to their first child between 1986 and 2004. After excluding women who had a diagnosis of endometriosis before their first birth, 709,090 women remained, of whom 3110 were diagnosed with endometriosis and treated in hospitals after their first birth. Investigators tracked women from the date they gave birth to their first child to either the date of the first diagnosis of endometriosis, the date of their 55th birthday, or December 31, 2004, the date on which investigators retrieved the dataset, whichever came first.

Investigators looked both at cesarean-scar endometrioma and general pelvic endometriosis. They postulated that since endometriosis results from uterine lining cells taking hold and growing outside of the uterus, cesarean surgery could disperse these cells throughout the pelvis, not just seed them into the uterine wound.

After accounting for factors that were associated both with endometriosis and cesarean delivery (maternal age at first delivery; BMI; smoking; and years of involuntary childlessness before first delivery), none of which had any appreciable effect, they found that having at least one cesarean nearly doubled the risk of developing endometriosis (hazard ratio: 1.8). This calculated to 1 additional case of endometriosis within 10 years for every 325 women undergoing cesarean surgery. Having multiple cesareans didn't appear to further increase the risk. Both women with only vaginal births and women with cesareans had new diagnoses of endometriosis, but a graph of the cumulative incidence rates showed that the line angled upward much more steeply as time passed in women with cesareans compared with women with only vaginal births.

The incidence rate of cesarean-scar endometrioma specifically was 1 per 1000 among women having cesareans. This may be considered a minimum since the data registry would not capture women who had cesarean-scar endometrioma but who either never received the correct diagnosis or were never admitted to a hospital for treatment.

The Swedish analysis has added to our knowledge of the relationship between cesarean surgery and endometriosis. It gave us an incidence rate for cesarean-scar endometrioma and showed that cesarean surgery also is associated with increased likelihood of developing generalized pelvic endometriosis of sufficient severity to require in-hospital treatment. Preventing that primary cesarean can play a critical role in reducing the number of women who will deal with the pain, complications and need for treatment of endometriosis that resulted from their cesarean surgery. When considering cesarean surgery, women should be told of the excess risk of developing generalized pelvic endometriosis and cesarean-scar endometrioma and their consequent complications (pain, irregular bleeding, infertility) as part of the informed decision-making process.

Did you know that an increase in endometriosis rates is a possible consequence of cesarean section? Are the women you are teaching and working with aware of this potential development and what it might mean? Do you consider this something that you would share in your role as Doula? Childbirth Educator? Midwife? OB? Let us know in the comments. - SM

References

Andolf, E., Thorsell, M., & Kallen, K. (2013). Caesarean section and risk for endometriosis: a prospective cohort study of Swedish registries. BJOG. doi: 10.1111/1471-0528.12236
http://www.ncbi.nlm.nih.gov/pubmed/23663181

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