Comparison of natural cycles versus hormone replacement treatment cycles
for endometrial preparation prior to frozen-thawed embryo transfer: a
retrospective cohort study from 9733 cycles
Abstract
Objective To compare the effectiveness of natural cycles (NC) and
artificial cycles (AC) in women undergoing frozen-thawed embryo transfer
(FET) after in vitro fertilization (IVF). Design Retrospective cohort
study. Setting Public fertility center in China. Population We studied
9733 women undergoing the first cycle of FET over a 3-year period (June
2014 - December 2017). All women were followed-up until one year after
embryo transfer. Methods The type of endometrial preparation was
determined by the treating physician’s preference, based on patients’
characteristics. Women with regular ovulation were allocated to natural
cycles (n=1676), while patients who were reluctant to frequently
monitoring or living far from the hospital were allocated to artificial
cycles (n=8057). A logistic regression model was used to assess the
association between endometrial preparation and clinical outcomes while
adjusting for potential confounders. Main outcome measures Live-birth
rate was primary outcome while miscarriage rate, clinical pregnancy
rate, preterm birth rate, and ectopic pregnancy rate were secondary
outcomes. Results In the adjusted model, type of endometrial preparation
did not affect live birth (OR, 0.89; 95%CI, 0.79-1.01), clinical
pregnancy (OR, 0.96; 95%CI, 0.85-1.09), preterm birth (OR, 1.09;
95%CI, 0.90-1.33) and ectopic pregnancy (OR, 0.77; 95%CI, 0.36-1.61),
while AC significantly increased the miscarriage rate (OR, 1.38; 95%CI,
1.11-1.73, P=0.004). Conclusion In women undergoing FET, natural cycles
and artificial cycles resulted in comparable live birth rate while
miscarriage rate was higher in artificial cycles.