Frequency of intrauterine adhesions after D+C

Asherman's syndrome is commonly an iatrogenic complication of D&C (and less commonly from other intrauterine surgery), characterized by intrauterine adhesions (IUA) and/or fibrosis (scarring without adhesions), leading to infertility and recurrent miscarriage if untreated. Furthermore, infertility/subfertility may persist after removal of adhesions (overall live birth rates in recent reviews are around 40%), and is associated with obstetric complications in future pregnancies. Asherman's syndrome is often described as a very rare condition, however if one considers incidence studies in the medical literature, it becomes clear that this is untrue. Although the risk of acquiring Asherman's syndrome increases with the number of D&C procedures, even a single D&C can lead to Asherman's syndrome. Note that Asherman's syndrome can also be caused by endometrial tuberculosis (rare in the US, Europe, and Australia/New Zealand) or other intrauterine surgery, although avoidable injury to the basal endometrium usually occurs from blind instrumentation.  

Over the years there have been several studies investigating the incidence of Asherman's syndrome/intrauterine adhesions following treatment with D&C. Most of these studies were carried out in women who underwent D&C for miscarriage, a procedure often abbreviated as ERPC for evacuation of retained products of conception. Note that milder forms of IUA may not lead to symptoms of Asherman's syndrome and are not considered as such. In some cases authors specified the severity of IUA. In summary of these publications in peer-reviewed medical journals, the actual incidence of IUA after D&C for miscarriage ranges between 7.7% and 30%, and after a repeat procecure, up to 40%. There is some criticism about these studies as some of them are quite old, especially a 1960 study on women who underwent D&C in the post partum period (it is also a retrospective study which is open to bias). Yet most of the criticism is not directed at the 50 year old study, but to more recent ones investigating the frequency of IUA in women undergoing D&C for miscarriage management. Perhaps the reason for this is that D&C is considered 'standard care' for miscarriage treatment and acceptance of the relatively high risks would raise questions about the validity of such an approach as 'standard care'.

Regardless of study date, there is little reason to suspect that incidence rates would change as the techniques used are for the most part the same today as 50 years ago and the main cause of IUA is blind instrumentation in a uterus softened by the presence of hormones (as in pregnancy). The low estrogen/ high progesterone environment in a recently pregnant uterus are also thought to favour adhesion formation (note: this is why estrogen therapy is given to women after corrective adhesiolysis surgery). Even the more recent manual vacuum aspiration has been associated with IUA (Dalton et al, 2006). Furthermore, sharp/blunt/suction D&C are often all used in the same procedure. Anyone who is familiar with the literature on Asherman’s syndrome will know that the references below are cited as references in recent review papers (see Yu et al,2008; Kodaman and Arici, 2007).

Another potential criticism about these studies is that they are not RCTs. (Tam et al, 2002 is an RCT but it does not meet the criteria for inclusion in the Cochrane Collaboration 's library (click here for more details). RCTs meet the most rigorous standards of scientific methodology. Unfortunately, to date there are NO RCTs on Asherman’s syndrome (including etiology and treatment) in the Cochrane database.

According to available studies, the following incidence rates have been reported:

1. Adoni et al (1982) found the incidence of IUA to be 30.9% after D&C for a ‘late’ miscarriage. This is taken to mean a missed or delayed miscarriage where the products of conception have not been expelled despite the pregnancy’s failure. IUA were detected via hysterography.

2. Golan et al.(1992) did a prospective analysis of 60 women and found that 16.7% of women undergoing D&C for missed miscarriage had IUA detected by hysteroscopy (gold standard method of diagnosis).

3. Friedler et al (1993) also did a prospective study on women with missed miscarriages who underwent D&C and found that 16 of the 98 patients, or 16.3%, had IUA detected by hysteroscopy.

4. Romer et al’s (1994) prospective study diagnosed IUA in 30.2% of women who had D&C for either missed or incomplete miscarriage. This was diagnosed hysteroscopically.

5. Westendorp et al (1998) prospectively examined wome who had repeat D&C for incomplete miscarriage or retained POC (after either miscarriage or delivery) and found that on hysteroscopy, a whopping 40% of them had IUA. 30% were severe in nature.

6. Tam et al (2002) performed a prospective study on IUA incidence after D&C for missed or incomplete miscarriage and compared it to women treated expectantly or using misoprostol. They found that 7.7% of women in the D&C group developed IUA while none developed it in the misoprostol group or expectant group. Again, hysteroscopy, was used for detection.

7. Eriksen and Kaestel (1960) reported in their retrospective analysis that approximately 25% of women undergoing post partum curettage developed IUA.

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Asherman’s syndrome is estimated to affect 5% of the population (prevalence). There are several reasons why the prevalence would be lower than the incidence. One obvious explanation is that not all women undergo D&Cs. The exact prevalence is unknown as many cases are not diagnosed due to a lack of awareness about the condition both by patients and doctors. There could be several cases of undiagnosed Asherman's syndrome described as 'unexplained infertility'. The condition is not detected by routine gynecological examinations (eg. ultrasound, blood tests etc.) and many women do not undergo hysteroscopy, the gold standard for diagnosis. Furthermore a proportion of Asherman's syndrome  cases may not have personal or clinical implications if a (further) pregnancy is not desired (thus these women would be unaware of their infertility/subfertility or of any obstetric complications associated with the condition).

The misconception that Asherman's syndrome is rare and that D&C is safe for fertility is perpetuated by the neglect the condition receives from the medical community as well as studies which claim to show that fertility is not affected in women who undergo D&C. One recent study known as the acronym MIST for miscarriage treatment randomised controlled trial (BMJ 2009;339:b3827), concluded that there was no significant difference in fertility outcome following expectant, medical or surgical treatment of miscarriage. However, each of the different groups of the study contained women who had previous miscarriages and ERPC (ie D&C). These were roughly the same among study respondents: 35% had a previous pregnancy loss, and 37% had a previous ERPC. Since the study groups did not differ significantly from each other, an equal number
 of women with prior D&Cs were allocated to each group. However, this could be regarded as a misclassification bias that could confound the effects on fertility of individual treatment methods and hence the study outcome. In effect, the authors assumed from the outset of the study that miscarriage treatment had no subsequent effect on fertility, an assumption which was incorporated into the study design, so it is not surprising that the study outcomes confirmed their assumption. Tellingly, the authors concluded that women with previous miscarriages were significantly less likely to subsequently give birth, although they seem oblivious to the possibility that previous method of miscarriage management (ie. D&C) could have influenced this outcome. This illustrates how poor study design can occur even in an RCT and lead to a possible skewing of results.

As can be gleaned from the above studies on IUA incidence after D&C for miscarriage, the advantages of D&C do not outweigh the potential risks and harms for most women, yet for reasons that do not take into account patient rights and violate the oath of doctors to do no harm, D&Cs continue to be the first line of therapy even with the existence of safer alternatives. D&C is no longer the only choice available to women who miscarry. Alternative methods such as medical management (ie. misoprostol) and visually guided hysteroscopic removal of retained products of conception are effective and can avoid injury and subsequent complications.

The first step towards change would be to accept that Asherman’s syndrome is NOT rare.

REFERENCES (in order of appearance in text)

Dalton VK, Saunders NA,Harris LH, Williams JA, Lebovic DI. Intrauterine adhesions after manual vacuum aspiration for early pregnancy failure. Fertil Steril 2006;85(6):1823 e1-3.
Kodaman, PH and Arici, A. Intra-uterine adhesions and fertility outcome: how to optimize success? Curr Opin Obstet Gynecol 2007;19(3):207-14.

Yu, D, Wong, YM, Cheong, Y, Xia, E, and Li, TC. Asherman syndrome--one century later. Fertil Steril 2008;89(4):759-79.

Adoni, A, Palti, Z, Milwidsky, A, and Dolberg, M. The incidence of intrauterine adhesions following spontaneous abortion. Int J Fertil 1982;27(2):117-8.

Golan, A, Schneider, D, Avrech, O, Raziel, A, Bukovsky, I, and Caspi, E. Hysteroscopic findings after missed abortion. Fertil Steril 1992;58(3):508-10.

Friedler, S, Margalioth, EJ, Kafka, I, and Yaffe, H. Incidence of post-abortion intra-uterine adhesions evaluated by hysteroscopy--a prospective study. Hum Reprod 1993;8(3):442-4.

Romer, T. Post-abortion-hysteroscopy--a method for early diagnosis of congenital and acquired intrauterine causes of abortions. Eur J Obstet Gynecol Reprod Biol 1994;57(3):171-3.

Tam, WH, Lau, WC, Cheung, LP, Yuen, PM, and Chung, TK. Intrauterine adhesions after conservative and surgical management of spontaneous abortion. J Am Assoc Gynecol Laparosc 2002;9(2):182-5.

Westendorp, IC, Ankum, WM, Mol, BW, and Vonk, J. Prevalence of Asherman's syndrome after secondary removal of placental remnants or a repeat curettage for incomplete abortion. Hum Reprod 1998;13(12):3347-50.

Eriksen J, Kaestel C. The incidence of uterine atresia after post-partum curettage. A follow-up examination of 141 patients. Dan Med Bull 1960; 7:50-1.

Smith L, Ewings P. Incidence of pregnancy after expectant, medical, or surgical management of spontaneous first trimester miscarriage: long term follow-up of miscarriage treatment (MIST) randomised controlled trial BMJ 2009;339:b3827.