Background: In women treated by assisted reproductive technology (ART), early pregnancy loss (EPL) reduces the initial success. Risk factors for EPL, however, have not been comprehensively studied. This study assesses some potential risk factors in ART pregnancies.
Methods: Altogether 1196 pregnancies, defined as serum hCG >or=10 IU/l on day 16 +/- 1 after oocyte retrieval, were included in this study. EPL was defined as pregnancy loss that occurred before 6-7 weeks gestation. Risk factors investigated were maternal age, body mass index (BMI), smoking and polycystic ovary syndrome (PCOS) status, infertility aetiology, response to stimulation, quality and number of embryos replaced and treatment type.
Results: Overall EPL was 16%. The risk of EPL was not linearly related to either age or BMI. Though women >40 years old had an increased risk, this was not significant after adjusting for other factors. The risk in both lean (BMI <18.5 kg/m(2)) and very obese (BMI >35 kg/m(2)) women was also not significantly higher in multivariate analysis. There was no effect of PCOS. Smoking or transfer of 'poor quality' embryo(s) was associated with a significant increased risk of EPL after adjusting for other factors.
Conclusion: Smoking and transferring poor quality embryos increased EPL, while the effects of age, obesity and other risk factors were not significant in a multivariate analysis.