Main findings
We found no statistically significant difference in the live birth rate between NC and AC for endometrial preparation. Our results are in line with those of other studies in recent literature11-13. Our study of no difference between NC and AC contrasts with studies that found a higher live birth rate with AC14,15. However, these studies relied on home ovulation predictor kits in NC or without serum hormone analysis in AC cycles and may be less precise in evaluating ovulation. In addition, the sample size was quite small.
Our study demonstrated a higher miscarriage rate in AC groups. These findings are similar to results from previous studies. A prospective study of 570 cycles found a higher miscarriage rate in the AC group but only included young women with regular menstrual cycles16. A retrospective study of 1677 FET cycles found that the miscarriage rate was significantly higher in the AC group both in own-egg and ovum-donor patients17.
Our findings contrast with several other retrospective studies showing similar miscarriage rates between NC and AC. One retrospective cohort study reported a comparable miscarriage rate between NC and AC after adjusting for potential confounders, while the AC group harms obstetric outcome7. Although this study had a relatively larger sample size, it was limited in its inclusion criteria of regular ovulatory cycles and at most two previous ET cycles.