Fig. 18.1
Traditional classification of congenital uterine anomalies as described by the American Fertility Society (From AFS [8], with permission)
However, since that classification, a plethora of publications appeared in the literature describing complex congenital anomalies, which were not accounted for in the original classification system. Furthermore, although recent advances in imaging are now allowing for subtle differences between anomalies to be detected, the classification did not provide clear definitions which would permit making a differential diagnosis between them [9]. For example, it was difficult to differentiate between a complete bicornuate uterus and a didelphys uterus, and between a subseptate uterus and an arcuate uterus. For this reason several novel classifications were proposed, chief amongst which was the VCUAM classification, which created the subdivisions of the vagina, cervix, uterus and associated malformations in order to systematically describe anomalies [10] and the Embryological clinical classification for female genitourinary problems proposed by Acien and Acien originally in 1992 and subsequently revised and updated in 2011 [6, 11]. Unfortunately, neither of these classifications were universally adopted mainly due to the complexity of their nature and also because some of the original difficulties with the AFS classification remained unresolved. For this reason the European Society for Gynaecological Endoscopy (ESGE) and the European Society for Human Reproduction and Embryology (ESHRE) combined to form a working group in order to create a new classification system. The final classification was published jointly in 2013 and received the wide acceptance of the scientific community experts through formal voting procedures [12]. The new classification system (Figs. 18.2 and 18.3) consists of descriptions for all female genital tract malformations (not just uterine) and also provides quantitative guides to allow for diagnosis and differentiation between different anomalies. The entities of arcuate uterus and didelphys uterus have been abolished, and are now incorporated in the subdivisions of the septate and bicorporeal uteri. Specifically, the septate uterus has been defined as the uterus with normal outline and an internal indentation at the fundal midline exceeding 50 % of the uterine wall thickness, while the bicorporeal (previously known as bicornuate) uterus has been described as it is characterized by the presence of an external indentation at the fundal midline exceeding 50 % of the uterine wall thickness. Finally the anomalies for the cervix and vaginal have all been accounted for, and complex genital tract malformations can be coded according to a UCV (Uterus, Cervix, Vagina) system, similar to the TNM system.
Fig. 18.2
New classification of congenital uterine anomalies as described by ESHRE/ESGE (From Grimbizis et al. [12], with permission)
Fig. 18.3
New classification of female genital tract anomalies as described by ESHRE/ESGE (From Grimbizis et al. [12], with permission)
Diagnosis
Accuracy
The correct diagnosis of congenital uterine anomalies is a difficult task for a number of reasons. Firstly, because of the use of different classification systems, as already mentioned, and also secondly, because of the use of different diagnostic modalities. The modalities used for diagnosing congenital uterine anomalies can be 2-dimensional ultrasound (2D US), 3-dimensional ultrasound (3D US), saline-infusion ultrasound (SI US), hysterosalpingography (HSG), magnetic resonance imaging (MRI), hysteroscopy and laparoscopy. All of these modalities have different sensitivities, specificities, positive predictive values (PPV) and negative predictive values (NPV). As a result they are not all appropriate for definitive diagnosis and classification of subtypes of anomalies. In a recent systematic review, all these modalities were reviewed and classified into classes Ia, Ib and Ic, according to their accuracy and ability to both identify congenital uterine anomalies and also diagnose the specific subtypes [13]. The results are shown in Tables 18.1 and 18.2. It was found that the most accurate investigations that could diagnose and classify congenital uterine anomalies, namely class Ia investigations, where combined hysteroscopy and laparoscopy, 3D US, SI US, and possibly MRI. Hysteroscopy alone was described as a class Ib investigation because it can accurately diagnose the presence of a congenital uterine anomaly (and can therefore belong to Class I), but is unable to correctly classify the subtype of anomaly as it does not assess the external contour of a uterus. Finally, 2D US and HSG were classified as class II investigations as it was found that they cannot reliably identify or diagnose congenital uterine anomalies.
Table 18.1
Accuracy of different investigations in the diagnosis of congenital uterine anoamlies
Diagnostic modalities | Cases (n) | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | Accuracy (%) |
|---|---|---|---|---|---|---|
2D US | 350 | 56 | 99 | 96 | 87 | 84 |
HSG | 625 | 78 | 90 | 83 | 91 | 86 |
SIU | 486 | 93 | 99 | 97 | 98 | 97 |
3D US | 679 | 100 | 100 | 100 | 100 | 100 |
MRI | 24 | 100 | 100 | 100 | 100 | 100 |
Hysteroscopy laparoscopy | Used as gold standard | |||||
Table 18.2
Classification of different investigations according to their diagnostic accuracy
Class | Investigation |
|---|---|
I (accuracy >90 %) | 3D US |
SI US | |
MRI | |
Hysteroscopy/laparoscopy | |
II (accuracy <90 %) | 2D US |
HSG |
Differences in Investigative Modalities
There are also other things to consider other than the accuracy and reliability of these investigative modalities, as they are so intrinsically different (Table 18.3). For example: invasiveness, cost, familiarity, availability and potential uses in the context of clinical research. Because of all these differences, it remains to be decided what the ideal protocol of screening and diagnosis of congenital uterine anomalies in women of high risk actually is. Interestingly, with the publication of the new ESGE/ESHRE classification for congenital uterine anomalies, the research community is slowly moving away from the long held concept that hysteroscopy and laparoscopy should be the gold standard of diagnosis. The reason being that investigations such as 3D US and MRI offer the additional advantage of storing images and allowing precise measurements of aspects of the anomaly, such as the septum, or external uterine wall indentation. It therefore could be that theoretically 3D US and MRI replace combined hysteroscopy and laparoscopy as the gold standard method of choice. However, in day to day clinical practice, it is most likely that different investigations will complement each other and the final diagnosis, particularly in complex cases, will be formed after the combined assessment of two or more different investigative modalities.
Table 18.3
The advantages and disadvantages of different diagnostic modalities used to diagnose congenital uterine anomalies
Diagnostic modalities | Accurate | Non-invasive | Measurement& storage | Availability/access | Cost | Comments |
|---|---|---|---|---|---|---|
2D US | x | ✓ | ✓ | ✓ | Low | Role in screening |
3D US | ✓ | ✓ | ✓ | Variable | Low | Most advantageous |
SIU | ✓ | x | ✓ | Variable | Low | Increases accuracy |
HSG | x | x | x | ✓ | Low | Concurrent tubal assessment |
MRI | ✓ | ✓ | ✓ | Variable | High | Useful in complex cases |
Hysteroscopy laparoscopy | ✓ | x | x | ✓ | High | Concurrent treatment |
Epidemiology
Previous Inconsistencies
The true epidemiology of congenital uterine anomalies has been a matter of debate for several decades. The reported prevalence for different populations differed so much that it was difficult to even ascertain whether it was a common or rare problem. The reason for this stems largely from points raised earlier. Firstly, the classifications for congenital uterine anomalies were not being consistently used, and it was therefore difficult to combine epidemiological data. Secondly, the investigative modalities used to assess the prevalence were different and therefore the accuracy/pick-up rate was different amongst different studies. Finally, the populations examined were not homogenous which again made pooling of data more difficult. It is therefore quite representative that on an initial review of the literature over the last 35 years (Table 18.4), the reported rates for congenital uterine anomalies can vary from 0.16 to 10.8 % for the general population [14, 15], from 1 to 48.9 % for the infertile population [16, 17], and from 0.5 to 65.8 % for the recurrent miscarriage population [18, 19].
Table 18.4
The variation of reported prevalence of congenial uterine anomalies in different populations over the last 35 years
Population | Estimated prevalence (%) |
|---|---|
General | 0.2–10.8 |
Infertile | 1.0–48.9 |
Recurrent miscarriage | 0.5–65.8 |
New Findings
For this reason, recent systematic reviews have attempted to estimate the true prevalence of congenital uterine anomalies based on studies that have used accurate investigations (i.e. Class I investigations as defined above), clear description of patient populations, and have classified the anomalies clearly according to the AFS classification, which has been the most widely accepted classification prior to that of ESHRE/ESGE [13, 20]. The prevalence in these reviews was estimated as 5.5–6.7 % for the general population, 7.3–8.0 % for the infertile population, and 13.3–16.7 % for the recurrent miscarriage population. When looking at the different types of congenital uterine anomalies, it appears that overall the most prevalent types of anomalies are in order: arcuate, septate, bicornuate, didelphys, Unicornuate and others (e.g. hypoplastic, T-shaped, rare/complex). The exact percentages can be seen in Table 18.5.
Table 18.5
Estimates of prevalence of different congenital uterine anomalies according to high quality studies using high accuracy investigations for diagnosis (data from two systematic reviews)
Population | Total (%) | Arcuate (%) | Septate (%) | Bicornuate (%) | Didelphys (%) | Unicornuate (%) | Others (%) |
|---|---|---|---|---|---|---|---|
General | 5.5–6.7 | 3.9–4.9 | 2.0–2.3 | 0.3–0.4 | 0.03–0.3 | 0.03–0.1 | 0–0.1 |
Infertile | 7.3–8.0 | 1.8–1.9 | 3.0–3.5 | 0.8–1.1 | 0.2–0.3 | 0.4–0.5 | 0.7–0.9 |
Recurrent miscarriage | 13.3–16.7 | 2.9–12.2 | 5.0–5.3 | 1.0–2.1 | 0.1–0.6 | 0.4–0.5 | 0.6–0.9 |
Important Observations
There are two interesting epidemiological observations to be made: First, the infertile population has a higher rate of septate uteri but a lower rate of arcuate uteri compared to the general population. At first glance, one might assume that this implies that infertility is associated with the septate uterus. However, there is no logical or plausible explanation for why the arcuate uterus would be less prevalent in the infertile population compared with the general population, as embryologically it is essentially ‘a very small septum’, making this finding counterintuitive. The second observation is that despite both reviews including only high quality studies, the estimations of the prevalence for the arcuate uterus in the recurrent miscarriage population vary between 2.9 and 12.2 %. The most reasonable explanation for both these observations is that although there may be a link between infertility and the septate uterus, there must be a high degree of subjectivity when diagnosing an arcuate or a seubseptate uterus. For example, in the infertile population some investigators may have diagnosed a subseptate uterus where others would have diagnosed an arcuate uterus, while in the recurrent miscarriage population some authors may have diagnosed an arcuate uterus where others may have merely diagnosed a normal variant uterus. Overall, however, from an epidemiological standpoint, congenital uterine anomalies seem significantly increased in the recurrent miscarriage population, and marginally increased in the infertile population, with a tendency towards higher rates of septate uteri. With the introduction of the new ESHRE/ESGE classification, more objective diagnoses will hopefully allow for well-designed studies to estimate even more accurately the true prevalence of the congenital uterine anomalies in different population groups.
Reproductive Impact
Epidemiological associations would suggest that congenital uterine anomalies are higher in women with infertility and recurrent miscarriage, and therefore by extrapolation have an adverse impact on reproductive performance. However, it is quite difficult to directly prove this association, and also it is important to remember that more than 5 % of the general/fertile population of women will also have some kind of congenital uterine anomaly. Prospective and retrospective cohort studies have attempted to ellucidate this association by comparing reproductive outcomes of women with normal uteri versus uteri with congenital uterine anomalies. The outcomes of interest are generally clinical pregnancy rates (relating to infertility), miscarriage rates (either first or second trimester), and obstetric complications (most commonly preterm labour and fetal malpresentation). Although in the context of reproductive surgery in assisted conception one will instantly be drawn to the data regarding the clinical pregnancy rates, it is important to remember that the ultimate goal is to improve the final live birth rate or baby take-home rate. Therefore the implications of congenital uterine anomalies are equally important in the context of conception as they are for the first trimester, second trimester and third trimester/labour events.
Impact on Clinical Pregnancy Rates
A recent meta-analysis of all studies available [21] has attempted to clarify the associations between congenital uterine anomalies and reproductive outcomes (Table 18.6). It showed that compared to women with normal uteri, women with septate uteri had significantly reduced rates of clinical pregnancies (RR 2.53; 95 % CI 1.54–4.18; p < 0.001). Women with arcuate uteri did not show a significant reduction in clinical pregnancy rates (RR, 1.03; 95 % CI, 0.94–1.12; p = 0.51), although only two studies were analysed [14, 22], one of which used HSG alone, which is a suboptimal method for diagnosing and classifying uterine anomalies. For the rarer anomalies such as bicornuate, didelphys and unicornuate uteri, there was a trend towards reduced clinical pregnancy rates, which however did not reach statistical significance (RR, 0.87; 95 % CI, 0.68–1.11; p = 0.25). Again the numbers of cases were small, the investigations used were not optimal and the heterogeneity was high (I2 = 86 %).
Table 18.6
Meta-analysis of studies assessing the reproductive impact of different congenital uterine anomalies
Anomaly | Conception rate | First trimester miscarriage | Second trimester miscarriage | Preterm labour | Fetal malpresentation |
|---|---|---|---|---|---|
Arcuate | 1.03 (0.94–1.12) | 1.35 (0.81–2.26) | 2.39 (1.33–4.27)** | 1.53 (0.70–3.34) | 2.53 (1.54–4.18)*** |
Septate | 0.86 (0.77–0.96)* | 2.89 (2.02–4.14)*** | 2.22 (0.74–6.65) | 2.14 (1.48–3.11)*** | 6.24 (4.05–9.62)*** |
Bicornuate | 0.86 (0.61–1.21) | 3.40 (1.18–9.76)* | 2.23 (1.05–5.15)* | 2.55 (1.57–4.17)*** | 5.38 (3.15–9.19)*** |
Didelphys | 0.9 (0.79–1.04) | 1.10 (0.21–5.66) | 1.39 (0.44–4.41) | 3.58 (2.00–6.40)*** | 3.70 (2.04–6.70)*** |
Unicornuate | 0.74 (0.39–1.41) | 2.15 (1.03–4.47)*
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