['To analyze natural cycle IVF (NC-IVF) results according to patient age, ovarian reserve status following the Bologna criteria, cause of infertility, and modification of the cycle with the use of GnRH antagonist.', 'Retrospective cohort study.', 'Tertiary-care university hospital.', 'Nine hundred forty-seven natural cycles carried out in 320 patients.', 'Analysis of 947 NC-IVF outcomes performed in one single center between January 2010 and December\xa02014.', 'Pregnancy rates per cycle started, per ET, and per patient, as well as ongoing pregnancy rate at a minimum of 12\xa0weeks of gestation.', 'Among the three age groups analyzed (≤35\xa0years, 36-39\xa0years, and ≥40\xa0years), pregnancy rates per cycle were significantly lower in the older group of patients (11.4% vs. 11.6% vs. 5.9%). In addition, miscarriage rate (7.7% vs. 34.4% vs. 50%) and ongoing pregnancy rate (10.6% vs. 7.6%vs. 3.0%) were negatively affected by patient age. However, no differences were observed according to patient ovarian reserve status, cause of infertility, or modification of the cycle with GnRH antagonist. The multivariate logistic regression confirmed that patient age was the only variable that could predict pregnancy in NC-IVF cycles (odds ratio, 0.93; 95% confidence interval, 0.88-0.98).'] Is age , independent from ovarian reserve status , the main prognostic factor in natural cycle in vitro fertilization?