Risk factors and clinical features of ovarian pregnancy: a case–control study

OBJECTIVE: To identify risk factors for ovarian pregnancy (OP) and compare clinical features between OP and tubal pregnancy (TP) patients. DESIGN: Case–control study. SETTING: University hospital. PARTICIPANTS: A case–control study was conducted from January 2005 to May 2014. Women diagnosed with OP were recruited as the case group (n=71), 145 women with TP and 146 with intrauterine pregnancy (IUP) were matched as controls at a ratio of 1:2:2. Women who refused interviews or provided incomplete information were excluded. RESULTS: OP risk was lower than TP risk in women with serological evidence of Chlamydia trachomatis infection (adjusted OR(1) 0.17, 95% CI 0.06 to 0.52), previous adnexal surgery (adjusted OR(1) 0.25, 95% CI 0.07 to 0.95), and current levonorgestrel emergency contraceptive use (adjusted OR(1) 0.24, 95% CI 0.07 to 0.78). In vitro fertilisation-embryo transfer (IVF-ET) carried a higher risk of OP (adjusted OR(1) 12.18, 95% CI 2.23 to 66.58) than natural conception. When Controlled by IUP women, current users of intrauterine devices (IUDs) carried a higher risk of OP than non-users of any contraceptives (adjusted OR(2) 9.60, 95% CI 1.76 to 42.20). β-Human chorionic gonadotropin (hCG) levels on the day of surgery were higher in OP patients than in TP patients (p<0.01). Women with OP were less likely to initially present with vaginal bleeding than those with TP (p=0.02). Moreover, shock (p=0.02), rupture (p<0.01), haemoperitoneum (p<0.01) and emergency laparotomy (p<0.01) were more common in the OP group than in the TP group. CONCLUSIONS: IVF-ET and IUD use may be risk factors for OP, and OP patients tend to have high β-hCG levels and a poor clinical outcome (shock, rupture, haemoperitoneum and need for emergency laparotomy). Our findings may contribute to the prevention and early diagnosis of OP.