Increased pregnancy complications following frozen-thawed embryo transfer during an artificial cycle

This study aimed to clarify the risks of adverse pregnancy outcomes in patients and their offspring after frozen embryo transfer (FET) during an artificial cycle (AC).

We conducted a retrospective cohort study that included all FET cycles and subsequent deliveries in a single centre between August 2013 and March 2016. Pregnancy, obstetric and neonatal outcomes were compared among patients treated during an AC or a natural cycle with luteal phase support (NC-LPS). Multivariate logistic regression was performed to evaluate the relationship between endometrial preparation schemes and pregnancy, obstetric and neonatal outcomes.

AC-FET was not a significant risk factor for clinical pregnancy rate, multiple birth rate or miscarriage rate after adjusting for potential confounders. However, AC-FET was a significant risk factor for ectopic pregnancy rate (adjusted odds ratio (AOR), 1.738; 95% confidence interval (CI), 1.086–2.781) and live birth rate (AOR, 0.709; 95% CI, 0.626–0.802). Regarding obstetric outcomes, AC-FET was found to be associated with an increased risk for hypertension disorder (AOR, 1.780; 95% CI, 1.262–2.510) and caesarean section (AOR, 1.507; 95% CI, 1.195–1.900). In multiples, birth weight (2550 g (2150–2900 g) in AC-FET vs. 2600 g (2350–2900 g) in NC-LPS; P = 0.023), gestational age (36.6 weeks (35.3–37.6 weeks) vs. 37.1 weeks (36.1–37.9 weeks); P < 0.001), and z-score (− 0.5 (− 1.1, − 0.0) vs. − 0.4 (− 1.0, 0.2); P = 0.009) were higher in the NC-LPS group than in the AC-FET group, although there were no differences in these variables among singletons.

Compared with NC-LPS, AC-FET seemed to have a negative effect on obstetric outcomes.