Frozen-thawed blastocyst transfer in natural cycle increase implantation rates compared artificial cycle.

Objective: To analyze global outcomes in frozen-thawed embryo transfer according to endometrial preparation with natural cycle and artificial cycle taking into account the developmental stage of the embryo.Methods: Retrospective cohort study, held in a tertiary-care university hospital with 1265 cycles for frozen-thawed embryo transfer of 860 patients, performed between January 2014 and December 2017. A total of 1097 embryo transfers were performed: 163 transfers in natural cycle (N), 531 in artificial cycle: transdermal estrogens and 403 with oral estrogens.Results: Demographical factors were similar in the three groups studied. When comparing the number of embryos transferred, the quality and the stage of embryos within the three groups there were no differences. Implantation rates were significantly higher in natural cycle. When adjusted depending on the developmental stage, blastocyst embryos transferred in natural cycle preparation had the highest implantation rate. Multiple pregnancies were also higher in natural cycle preparation. There were no significant difference between the groups in the clinical pregnancy rate, ongoing pregnancy, live birth, and miscarriages.Conclusions: Our results suggest that a natural cycle endometrial preparation assessing the disappearance of the dominant follicle by ultrasound increases implantation rates, especially when transferring blastocysts.

Age, independent from ovarian reserve status, is the main prognostic factor in natural cycle in vitro fertilization.

OBJECTIVE: 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. DESIGN: Retrospective cohort study. SETTING: Tertiary-care university hospital. PATIENT(S): Nine hundred forty-seven natural cycles carried out in 320 patients. INTERVENTION(S): Analysis of 947 NC-IVF outcomes performed in one single center between January 2010 and December 2014. MAIN OUTCOME MEASURE(S): Pregnancy rates per cycle started, per ET, and per patient, as well as ongoing pregnancy rate at a minimum of 12 weeks of gestation. RESULT(S): Among the three age groups analyzed (≤35 years, 36-39 years, and ≥40 years), 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). CONCLUSION(S): NC-IVF is a feasible and "patient-friendly" option to be offered to young patients, independent of their ovarian reserve status.