Interestingly, this study found a higher incidence of emergency laparotomy and shock in OP patients than in TP patients. Further, the incidence of haemoperitoneum during the operation was significantly higher in the OP group than in the TP group. These findings collectively indicate that OP patients tend to have a poorer prognosis thing than TP patients. Although our data is interesting and initially provide information focused on the aetiological research of OP, the recognised drawbacks of retrospective, hospital-based case–control studies must be acknowledged, and the quality of the outcome data may also be biased due to

recall bias and selection bias. Another important limitation of the study was the limited sample size due to the extremely low incidence of OP. In this study,

there were also a small number of OP patients who underwent IVF-ET, thus, despite the fact that IVF-ET appeared to be a high risk for OP, the CI was relative wide. Therefore, sample size should be enlarged and a prospective cohort study should be further designed to validate the results of this study. Conclusion Our findings indicated that IVF-ET and current IUD use are risk factors of OP, while previous adnexal surgery, a positive reaction to CT IgG antibody, and LNG-EC use are not associated more strongly with OP than TP. OP patients are more likely to have high β-hCG levels, accompanied by worse clinical outcomes (shock, rupture, haemoperitoneum and need for emergency laparotomy). These risk factors and

clinical features seem to have a high predictive value and may aid in early detection of OP, thereby enabling conservative treatment, reduced mortality and morbidity rates, preservation of fertility and lower overall costs of healthcare for OP. Supplementary Material Author’s manuscript: Click here to view.(2.3M, pdf) Reviewer comments: Click here to view.(164K, pdf) Footnotes Contributors: JZ conceived, designed and supervised the study as well as critically revised the manuscript. QZ and CL were responsible for drafting and revising the manuscript. W-HZ and G-JQ contributed to statistical analyses and participated in drafting part of the manuscript. M-XY and J-JY contributed to raw data collection. All authors substantially contributed to the revision of the manuscript. Funding: This work was supported by Shanghai Scientific and Technical Committee Grants (124119a4802). Competing interests: None. Patient consent: Obtained. Ethics approval: Ethics approval was AV-951 obtained from the Ethics Committee of the International Peace Maternity and Child Health Hospital. Provenance and peer review: Not commissioned; externally peer reviewed. Data sharing statement: Extra data can be accessed via the Dryad data repository at http://datadryad.org/ with the doi:10.5061/dryad.tn90g.
Fundus examination is a non-invasive evaluation of the retinal microcirculation and of the vascular damage caused by multiple cardiovascular risk factors.