Natural cycle versus artificial cycle in frozen-thawed embryo transfer: A randomized prospective trial

OBJECTIVE: To investigate whether there was a difference in pregnancy outcomes between modified natural cycle frozen-thawed embryo transfer (NC-FET) cycles and artificial cycles (AC)-FET in women who all had regular menstrual cycles. MATERIALS AND METHODS: One hundred seventy patients who met the inclusion criteria and had at least two cryopreserved embryos were included in a prospective randomized controlled trial. Eighty-five patients were randomized based on Bernoulli distribution into the following two groups: 1) Modified NC-FET using human chorionic gonadotropin for ovulation induction and 2) AC-FET, in which endometrial timing was programmed with estrogen and progesterone. The main studied outcome measure was the clinical pregnancy rate per cycle. RESULTS: No significant differences were found between the two groups with regard to the chemical, clinical, and ongoing pregnancy rates (48.2% vs 45.9%, p>0.05; 38.9% vs 35.3%, p>0.05; and 37.6% vs 34.1%, p>0.05, respectively), as well as the live birth or miscarriage rates per cycle (35.3% vs 31.8%, p>0.05; and 1.2% vs 1.2%, p>0.05, respectively). CONCLUSION: These findings suggest that although both FET protocols are equally effective in terms of pregnancy outcomes in women with regular menstrual cycles, NC-FET is more favorable because it requires no medication, has no adverse events, and has a significant cost reduction.