Cervical pregnancy in assisted reproduction: an analysis of risk factors in 91,067 ongoing pregnancies.

RESEARCH QUESTION: What is the frequency of cervical pregnancy in women undergoing assisted reproductive technologies (ART) and what are the risk factors? DESIGN: Case-control study of women undergoing assisted reproductive technology (ART) at 25 private assisted reproduction clinics run by the same group in Spain. Two control groups (tubal ectopic pregnancies and intrauterine pregnancies) were established. The main outcome measure was frequency of cervical pregnancy. Demographic, clinical factors and IVF parameters were assessed for their influence on cervical pregnancy risk. RESULTS: Thirty-two clinical pregnancies were achieved out of 91,067 ongoing pregnancies, yielding a rate of 3.5/10,000. Cervical pregnancies represented 2.02% of all ectopic pregnancies (32/1582). The main risk factors two or more previous pregnancies (OR 2.68; CI 1.18 to 6.07); two or more previous miscarriages (OR 4.21; CI1.7 to 10.43), one or more previous curettages (OR 3.99, CI 1.67 to 9.56), two or more previous curettages (OR 4.71; CI 1.19 to 18.66) and smoking (OR 2.82 CI 1.14 to 6.94). History of caesarean sections and tubal pregnancy was not associated with an elevated cervical pregnancy risk. Infertility conditions and endometrial thickness were similar across the three groups. The proportion of women from whom fewer than 10 oocytes were retrieved was higher in the clinical pregnancy group than in the IUP group. CONCLUSIONS: In ART, the main risk factors for cervical ectopic pregnancy are a history of at least two pregnancies, miscarriages, at least one curettage and smoking. IVF parameters do not seem to influence the development of clinical pregnancies. Cervical pregnancies are less common in ART than previously reported, attributable to improvements in ART; a publication bias in early IVF reports cannot be ruled out.