Risk factors for ectopic pregnancy in the Taiwanese population: a retrospective observational study

The aim of this study is to explore the risk factors for ectopic pregnancy (EP) in the Taiwanese population and to identify any unknown risk factors for EP that could assist awareness and diagnosis. This retrospective case-control study utilizes Taiwan's National Health Insurance Research Database (NHIRD). Analysis was conducted with a one million sample database representative of the country's population. The case group comprised of 6637 individuals in the database that coded for EP using the ICD-9 classification system from January 2003 to December 2011. The control group comprised of 13,270 females matched by age that were never diagnosed with EP during the study period. This study provides an analysis of the risk factors of EP utilizing NHIRD. Among the 6637 people diagnosed with EP, logistic regression with age adjustment showed that the highest risk factor was endometriosis (OR = 8.84, CI 5.13-15.23), followed by polycystic ovary (OR = 7.74, CI 3.37-17.79) and benign neoplasm of the ovary (6.01, CI 2.18-16.54). All odds ratios were determined to be statistically significant at p < 0.001. This study has identified the diagnosis of endometriosis and polycystic ovaries as the two largest risk factors for EP in Taiwan, and has also newly identified benign neoplasm of ovary and uterine leiomyoma as risk factors for EP.