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.