Strengths and limitations
The majority of previous studies that have estimated the prevalence of
endometriosis were focused on women who were symptomatic of pelvic pain
or were undergoing fertility tests. Our study is the first to describe
the prevalence of endometriosis in women during pregnancy, regardless of
their previous gynaecological history. We found that the prevalence of
endometriosis in women attending our early pregnancy unit (5%) was
similar to that in women attending our general gynaecological diagnostic
clinic (6%).13
The main strength of our study is that it is a large prospective study
with clearly defined diagnostic criteria. All examinations were
performed by a single operator to avoid inter-observer variability.
Consecutive women were screened using a consistent approach to
ultrasound examination technique and the same high-quality ultrasound
technology. Consistent data collection was ensured and included multiple
demographic and clinical variables in order to examine possible
associations with the presence of endometriosis.
A possible limitation of our study is the lack of surgical or
histological confirmation of the diagnosis of endometriosis. However,
the diagnostic criteria were clearly defined in the study methodology
and expert ultrasound examination has been well-described in the
literature as having good concordance with laparoscopy for the detection
of moderate and severe endometriosis.11 In addition,
superficial peritoneal disease cannot be reliably detected on
transvaginal ultrasound and therefore the true prevalence of
endometriosis is likely to be higher than found in our study. However,
the clinical significance of superficial peritoneal endometriosis has
been recently questioned and its relevance in the context of adverse
pregnancy outcomes is unlikely to be comparable to that of ovarian and
deep disease.21 We were unable to detect deep or
ovarian endometriosis in some women who reported past diagnosis of
endometriosis. However, the subtype of their previous diagnosis was not
known and more than 80% had previously undergone surgical treatment.