Endometriosis is a common, chronic inflammatory disease defined by the presence of extrauterine endometrial tissue. The aetiology of endometriosis is complex and multifactorial, where several not fully confirmed theories describe its pathogenesis. This review examines existing theories on the initiation and propagation of different types of endometriotic lesions, as well as critically appraises the myriad of biologically relevant evidence that support or oppose each of the proposed theories. The current literature suggests that stem cells, dysfunctional immune response, genetic predisposition, and aberrant peritoneal environment may all be involved in the establishment and propagation of endometriotic lesions. An orchestrated scientific and clinical effort is needed to consider all factors involved in the pathogenesis of this multifaceted disease and to propose novel therapeutic targets to reach effective treatments for this distressing condition.

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Objective To compare the outcomes of operative cephalic births by Kielland forceps (KF), rotational ventouse (RV), or primary emergency caesarean section (pEMCS) for malposition in the second stage of labour in modern practise.Design Retrospective observational study.Population Data were included from 1291 consecutive full-term, singleton cephalic births between 2 November 2006 and 30 November 2010 with malposition of the fetal head during the second stage of labour leading to an attempt to deliver by KF, RV or pEMCS.Methods Maternal and neonatal outcomes of all KF births were compared with other methods of operative birth for malposition in the second stage of labour (RV or pEMCS).Main outcome measures Achieving a vaginal birth was the primary outcome and fetal (admission to special care baby unit, low cord pH, low Apgar, shoulder dystocia, Erb's palsy) and maternal (massive obstetric haemorrhage-blood loss of >1500 ml, sphincter injury, length of stay in hospital) safety outcomes were also recorded.Results Women were more likely to need caesarean section if RV (22.4%) was selected to assist the birth rather than KF (3.7%; adjusted odds ratio 8.20; 95% confidence interval 4.54-14.79). Births by KF had a rate of adverse maternal and neonatal outcomes comparable to those by RV and pEMCS in the second stage for malposition.Conclusions Our results suggest that, in experienced hands, assisted vaginal birth by KF is likely to be the most effective and safe method to prevent the ever rising rate of caesarean sections when malposition complicates the second stage of labour.Keywords Emergency caesarean section, Kielland forceps, rotational vaginal birth, rotational ventouse.