Internal medicine

Gestational diabetes

Small for gestational age

Biology

Odds ratio

Obstetrics

Endometriosis

Gestational hypertension

Gestational age

Gynecology

Pregnancy

Gestation

Genetics

Medicine

Human Reproduction

How is endometriosis associated with adverse maternal, fetal and neonatal outcomes of pregnancy? Women with endometriosis are at elevated risk for serious and important adverse maternal (pre-eclampsia, gestational diabetes, placenta praevia and Cesarean section) and fetal or neonatal outcomes (preterm birth, PPROM, small for gestational age, stillbirth and neonatal death). A number of studies have shown an association between endometriosis and certain adverse maternal and fetal outcomes, but the results have been conflicting with potential for confounding by the use of assisted reproductive technology. A systematic review and meta-analysis of observational studies (1 January 1990–31 December 2017) that evaluated the effect of endometriosis on maternal, fetal and neonatal outcomes was conducted. Studies were considered for inclusion if they were prospective or retrospective cohort or case–control studies; included women greater than 20 weeks gestational age with endometriosis; included a control group of gravid women without endometriosis; and, reported at least one of the outcomes of interest. Each study was reviewed for inclusion, data were extracted and risk of bias was assessed by two independent reviewers. The search strategy identified 33 studies (sample size, n = 3 280 488) for inclusion. Compared with women without endometriosis, women with endometriosis had higher odds of pre-eclampsia (odds ratio [OR] = 1.18 [1.01–1.39]), gestational hypertension and/or pre-eclampsia (OR = 1.21 [1.05–1.39]), gestational diabetes (OR = 1.26 [1.03–1.55]), gestational cholestasis (OR = 4.87 [1.85–12.83]), placenta praevia (OR = 3.31 [2.37, 4.63]), antepartum hemorrhage (OR = 1.69 [1.38–2.07]), antepartum hospital admissions (OR = 3.18 [2.60–3.87]), malpresentation (OR = 1.71 [1.34, 2.18]), labor dystocia (OR = 1.45 [1.04–2.01]) and cesarean section (OR = 1.86 [1.51–2.29]). Fetuses and neonates of women with endometriosis were also more likely to have preterm premature rupture of membranes (OR = 2.33 [1.39–3.90]), preterm birth (OR = 1.70 [1.40–2.06]), small for gestational age <10th% (OR = 1.28 [1.11–1.49]), NICU admission (OR = 1.39 [1.08–1.78]), stillbirth (OR = 1.29 [1.10, 1.52]) and neonatal death (MOR = 1.78 [1.46–2.16]). Among the subgroup of women who conceived spontaneously, endometriosis was found to be associated with placenta praevia, cesarean section, preterm birth and low birth weight. Among the subgroup of women who conceived with the use of assisted reproductive technology, endometriosis was found to be associated with placenta praevia and preterm birth. As with any systematic review, the review is limited by the quality of the included studies. The diagnosis for endometriosis and the selection of comparison groups were not uniform across studies. However, the effect of potential misclassification would be bias towards the null hypothesis. The association between endometriosis with the important and serious pregnancy outcomes observed in our meta-analysis, in particular stillbirth and neonatal death, is concerning and warrants further studies to elucidate the mechanisms for the observed findings. Dr Shifana Lalani is supported by a Physicians' Services Incorporated Foundation Research Grant, and Dr Innie Chen is supported by a University of Ottawa Clinical Research Chair in Reproductive Population Health and Health Services. Dr Singh declares conflicts of interests with Bayer, Abvie, Allergan and Cooper Surgical. All other authors have no conflicts of interests to declare. PROSPERO CRD42015013911.

Endometriosis and adverse maternal, fetal and neonatal outcomes, a systematic review and meta-analysis