title: Risk factors for ectopic pregnancy: a multi-center case-control study.
abstract: BACKGROUND
  Ectopic pregnancy (EP) is the leading cause of maternal death during the first trimester of pregnancy. A better understanding of EP risk can help prevent its occurrence. We carried out a multi-center, large-sample, case-control study to evaluate the risk factors for EP in Shanghai, China.
  
  
  METHODS
  Women who were diagnosed with EP (n = 2411) and women with intrauterine pregnancies (n = 2416) were recruited from five hospitals in Shanghai, China. Information regarding the sociodemographic characteristics; reproductive, gynecological and surgical history; and previous and current use of contraceptives was collected from all participants. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated and adjusted for potential confounding factors via multivariate logistic regression analysis.
  
  
  RESULTS
  The study revealed that the risk of EP was associated with the traditional risk factors including previous EP (Adjusted odds ratio [AOR] = 2.72, 95% CI: 1.83-4.05), previous Chlamydia trachomatis infection (Adjusted OR = 3.18, 95% CI: 2.64, 3.84), previous infertility (AOR = 2.18, 95% CI: 1.66-2.88), previous adnexal surgery (AOR = 2.09, 95% CI: 1.49-2.93), previous appendectomy (AOR = 1.64, 95% CI: 1.13-2.37), and previous use of intrauterine devices (IUDs) (AOR = 1.72, 95% CI: 1.39-2.13). Additionally, EP risk was increased following the failure of most contraceptives used in the current cycle including IUDs (AOR = 16.43, 95% CI: 10.42-25.89), oral contraceptive pills (AOR = 3.02, 95% CI: 1.16-7.86), levonorgestrel emergency contraception (AOR = 4.75, 95% CI: 3.79-5.96), and female sterilization (AOR = 4 .73, 95% CI: 1.04-21.52). Stratified analysis showed that in vitro fertilization and embryo transfer (IVF-ET) was the main risk factor for EP in women with tubal infertility (AOR = 8.99, 95% CI: 1.98-40.84), although IVF-ET showed no association with EP in women with non-tubal infertility (AOR = 2.52, 95% CI: 0.14-44.67).
  
  
  CONCLUSIONS
  In addition to the traditional risk factors, IVF-ET and current IUD use play dominant roles in the occurrence of EP. Attention should be given to women with tubal infertility who have undergone IVE-ET treatment.
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. downing@sjtu.edu.cn.|Institute of Embryo-Fetal Original Adult Disease Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China. downing@sjtu.edu.cn.
authors: Cheng
authors: C
authors: Li
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. weihong-zhao@hotmail.com.
authors: Wei-Hong
authors: WH
authors: Zhao
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. melodyqianzhu@126.com.
authors: Qian
authors: Q
authors: Zhu
authors: Department of Obstetrics and Gynecology, Songjiang Central Hospital, Shanghai, 201600, China. shujun-cao@163.com.
authors: Shu-Jun
authors: SJ
authors: Cao
authors: Department of Obstetrics and Gynecology, Songjiang Maternity and Child Health Hospital, Shanghai, 201620, China. pinghua661106@126.com.
authors: Hua
authors: H
authors: Ping
authors: Department of Obstetrics and Gynecology, Shanghai First People's Hospital, Shanghai Jiao Tong University, Shanghai, 200080, China. xixiaowei1966@126.com.
authors: Xiaowei
authors: X
authors: Xi
authors: Department of Obstetrics and Gynecology, Minhang Central Hospital, Shanghai, 201100, China. xiaoguo19711001@163.com.
authors: Guo-Juan
authors: GJ
authors: Qin
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. yanxiaohei00000@163.com.
authors: Ming-Xing
authors: MX
authors: Yan
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. zd621@hotmail.com.
authors: Duo
authors: D
authors: Zhang
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. qjchildren736@qq.com.
authors: Jun
authors: J
authors: Qiu
authors: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200030, China. zhangjian_ipmch@sjtu.edu.cn.|Institute of Embryo-Fetal Original Adult Disease Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China. zhangjian_ipmch@sjtu.edu.cn.
authors: Jian
authors: J
authors: Zhang
mesh_terms: D000328:Adult; D001062:Appendectomy / Q000706:statistics & numerical data; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D002690:Chlamydia Infections / Q000453:epidemiology*; D044363:Contraception, Postcoital / Q000706:statistics & numerical data; D003270:Contraceptive Agents / Q000627:therapeutic use; D004624:Embryo Transfer / Q000706:statistics & numerical data; D005260:Female; D005307:Fertilization in Vitro / Q000706:statistics & numerical data; D006801:Humans; D007247:Infertility, Female / Q000453:epidemiology*; D007434:Intrauterine Devices / Q000706:statistics & numerical data*; D016015:Logistic Models; D015999:Multivariate Analysis; D016017:Odds Ratio; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000453:epidemiology*; D012307:Risk Factors; D013245:Sterilization, Reproductive / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D003270:Contraceptive Agents