Pregnancy A biochemical pregnancy was defined as two consecutive positive rising (> 15IU/ml) serum hCG levels. A preclinical miscarriage was defined as two consecutive positive rising (> 15IU/ml) serum hCG levels, but no FHB at least 6 weeks post embryo transfer. A clinical pregnancy was defined as an intrauterine gestational sac with positive foetal heart activity seen at ultrasonography performed at least 6 weeks post-embryo transfer. A miscarriage was defined as a pregnancy loss before 20 weeks of gestation. The live birth delivery rate was defined as the number of live birth deliveries expressed per 100 initiated cycles, aspiration cycles or embryo transfer cycles (Zeghers-Hochschild et al., 2006).