Risk factors for pelvic endometriosis in women with pelvic pain or infertility: Gruppo Italiano per lo Studio dell’ endometriosi1

https://doi.org/10.1016/S0301-2115(98)00332-7Get rights and content

Abstract

Objective: The objective of the study was to analyse the relationship between selected characteristics and risk of pelvic endometriosis. Study design: Eligible for the study were 817 women with primary or secondary infertility or pelvic pain requiring laparoscopy. Of these, 393 were included for infertility and 424 for pelvic pain. Results: A total of 345 (42.2%) had a diagnosis of endometriosis and 472 did not have the disease. Multiparous women had endomertriosos less frequently than nulliparous, the estimated odds ratios (OR) were respectively 0.9 (95% confidence interval, CI, 0.5–1.6) and 0.4 (95% CI 0.2–0.7) in women reporting one and two or more births. In comparison with women reporting no spontaneous abortion, the estimated OR was 0.3 (95% CI 0.2–0.5) in those who reported ≥1 miscarriage. In comparison with women reporting menstrual cycles lasting ≥25 days subjects with totally irregular menstrual cycles had a reduced risk of endometriosis (OR 0.6, 95% CI 0.3–0.9). No significant association emerged between smoking, age at menarche and risk of endometriosis. Conclusions: this study confirms, with a different methodological approach to previously published studies, that multiparity, a history of abortion and lifelong irregular menstrual pattern decrease the risk of endometriosis in women with pelvic pain and infertility.

Introduction

Epidemiological studies have suggested that reproductive and menstrual history are associated with the risk of pelvic endometriosis [1], [2], [3], [4], [5], [6]. Nulliparous women were at increased risk of endometriosis in case–control studies conducted in Italy and in the US [1], [4], [5]. Age at menarche was younger in cases with endometriosis than in controls in a case–control study conducted in the US [1], but no significant association between age at menarche and endometriosis was reported in an Italian study [4].

With regard to the characteristics of menses, a lifelong regular menstrual pattern and heavy flows were associated with an increased risk of endometriosis [1], [4], [6], [7].

However, caution has been suggested in the interpretation of these findings, considering the potential biases which may act in epidemiological studies of this condition [7]. First of all, infertility and pelvic pain are clinical findings in endometriosis [8], and are often the reason for diagnostic procedures. This selective mechanism raises the frequency of infertile women or women with an abnormal menstrual pattern among the cases. In order to take this selection bias into account some studies have analysed only cases in which the diagnosis of endometriosis was an incidental finding in women who underwent surgery for other benign gynecological conditions [4]. However, this methodological approach may introduce other potential biases.

To re-analyze the epidemiological characteristics of pelvic endometriosis and reduce the potential difference in selective mechanisms between cases with the disease and the comparison group, we considered the reproductive and gynecological history of women with and without endometriosis who underwent laparoscopy for infertility or pelvic pain in a network of hospitals cooperating in the Gruppo Italiano per lo Studio dell’Endometriosi. This analysis may offer also the opportunity of reconsidering in a large data-set, the clinical impressions on risk factors for endometriosis.

Section snippets

Materials and methods

Eligible for the study were women with primary or secondary infertility or pelvic pain requiring laparoscopy consecutively observed in 15 obstetrics and gynecology departments in Italy. Women with a previous diagnosis of endometriosis were specifically excluded.

Infertility was defined as an active effort at pregnancy for 2 years or more, with no specific diagnostic work-up before laparoscopy, but participating centres agreed to exclude any women whose partner had severe oligozoospermia (<10×106

Results

Out of the 424 women included for pelvic pain and the 393 included for infertility, respectively 210 (49.5%) and 135 (34.4%) had a diagnosis of endometriosis. Among women with endometriosis who entered the study for infertility, 42 (31.1%) were at stage 1, 32 (23.7%) at stage 2, 38 (28.1)% at stage 3, 8 (5.9%) at stage 4 and in 15 cases (11.1%) information regarding the stage was missing. The corresponding figures for pelvic pain were: 46 women at stage 1 (21.9%), 39 at stage 2 (18.6%), 78 at

Discussion

Strengths and limitations of this study should be considered. This study offers the opportunity of analysing the characteristics of women with and without endometriosis undergoing laparoscopy with a specific indication: pelvic pain or infertility. Thus the results are not formally generalizable to the whole population.

This is the main limitation of this study. This “selected” control group may be cause of bias particularly in the analysis of obstetric and gynecological factors, but could be

References (18)

  • H Sangi-Haghpeykar et al.

    Epidemiology of endometriosis among parous women

    Obstet Gynecol

    (1995)
  • J.A Baron et al.

    The antiestrogenic effect of cigarette smoking in women

    Am J Obstet Gynecol

    (1990)
  • F Parazzini et al.

    The epidemiology of endometrial cancer

    Gynecol Oncol

    (1991)
  • J.A Rock et al.

    Pathogenesis of endometriosis

    Lancet

    (1992)
  • D.W Cramer et al.

    The relation of endometriosis to menstrual characteristics, smoking, and exercise

    J Am Med Assoc

    (1986)
  • D.E Houston

    Evidence for the risk of pelvic endometriosis by age, race and socioeconomic status

    Epidemiol Rev

    (1984)
  • T.A Mahmood et al.

    Menstrual symptoms in women with pelvic endometriosis

    Br J Obstet Gynaecol

    (1991)
  • F Parazzini et al.

    Pelvic endometriosis: reproductive and menstrual risk factors at different stages in Lombardy, northern Italy

    J Epidemiol Comm Health

    (1995)
  • F Parazzini et al.

    Risk factors for endometrioid, mucinous and serous benign ovarian cysts

    Int J Epidemiol

    (1989)
There are more references available in the full text version of this article.

Cited by (0)

1

The following clinicians are co-authors of the present paper: Milano, Istituto Mario Nejei, Milano (Fabio Parazzini), Benevento (Italo Ardovino, Elisario Struzziero); Bologna (Ettore Zanardi, Daniela Pungetti); Cagliari (Valerio Mais, Silvio Ajossa); Catania (Giovanni Mignemi, Luciano Di Leo); Ferrara (Albino Bianchi, Carlo Campobasso); Firenze (Gian Franco Scarselli, Gianluca Bracco); Milano “M. Melloni” (Piero Capetta, Carlo Bertulessi); Milano “Mangiagalli” (Simona Moroni, Patrizia Mazza, Paolo Vercellini, Pier Giorgio Crosignani); Parma (Alfio Bacchi Modena); Roma (Alessandro Casa); Torino “Mauriziano” (Marco Massobrio, Cristina Ansaldi); Torino “S. Luigi” (Gian Franco Trossarelli); Treviso (Maria Teresa Gervasi, Vittorio Marsoni); Trieste (Secondo Guaschino, Luigi-Troiano, Giuseppe Ricci); Varese (Paolo Beretta, Massimo Franchi).

View full text