RESUMEN
This longitudinal multicentre cohort study aimed to identify the role of the conception mode in infertile couples with an early pregnancy loss (EPL). All couples referred to the fertility clinic for the first time in the period 2002-2006 because of infertility were followed up to their first clinical pregnancy (n=1809). EPL was the outcome of 286 (15.8%) pregnancies. EPL rates for the different conception modes were as follows: spontaneous 14.5% (125/864), ovulation induction 15.8% (42/266), intrauterine insemination 25.0% (5/20), intrauterine insemination combined with ovarian stimulation 18.2% (37/203), IVF 16.3% (31/190), intracytoplasmic sperm injection (ICSI) 14.9% (30/202) and frozen embryo transfer (FET) 26.2% (16/61). After adjusting for female age, male age, hospital, obstetric history, female smoking habit, male alcohol use, menstrual cycle type and infertility diagnosis, the EPL rate after FET was significantly increased (odds ratio 2.2, 95% CI 1.14-4.19) compared with spontaneous conception. Embryo quality was comparable in fresh and frozen embryos. Other fertility treatments showed no increased miscarriage rate. Therefore, it is concluded that even after adjustment for confounding factors conception through FET remained an independent risk factor for EPL. Other modes of conception were not related with EPL.