Statistical analyses
Statistical analyses were performed
using SPSS 22.0 (IBM, Armonk, USA). Quantitative variables were
presented as means ± standard deviations and categorical variables were
expressed as frequencies and percentages. The data were analyzed using
the Chi-squared test, Fisher’s exact test, one-way analysis of variance
(ANOVA) or Bonferroni testas appropriate. Logistic regression analysis
was performed to explore the effects of different blastocyst transfer
strategies on live birth after controlling for potential confounders
including female age, female BMI, duration of infertility and
endometrial thickness. A two-sided P < 0.05 was
considered to be statistically significant.