Statistical analysis
The pregnancy outcomes in our study
included
the clinical pregnancy rate (CPR), spontaneous abortion rate (SAR), and
live birth rate (LBR). Clinical pregnancy was defined as detection of a
gestational sac on ultrasound at 7 gestational weeks16. In China, spontaneous abortion is defined as the
spontaneous loss of a clinical pregnancy < 28 gestational
weeks, and live birth as the survival of delivery ≥ 28 gestational
weeks.
The patients were divided into four groups according to the 1st, 2nd,
and 3rd quartiles of the overall average distance distribution, which
represent different uterine corpus inclinations (Group 1, ≤ 1.98 cm, n =
131; Group 2, 1.99-2.19 cm, n = 133; Group 3, 2.20-2.50 cm, n = 130;
Group 4, ≥ 2.51 cm, n = 129).
Multivariable logistic regression models were calculated for the whole
cohort, with the uterine corpus inclination as the main variable of
interest. The potential risk factors entered into the multivariable
regression model were those that showed clinical relevance or those with
a P value < 0.2 on univariate analysis. The included
variables were carefully selected based on the number of events
available to ensure the stability of the regression equation. Adjusted
odds ratios (OR) and their 95% confidence intervals (CI) were
calculated to analyze the independent effect of the uterine corpus
inclination on the pregnancy outcomes. As the migratory duration before
implantation differed between cleavage-stage embryos and blastocysts, we
analyzed the two stages separately. The number of cleavage ET cohort was
126, and the number of blastocyst transfer cohort was 400.
The second aim of the study was to determine the cut-off point for the
average distance that would predict pregnancy outcomes. Receiver
operating characteristic (ROC) curves were used to estimate the
sensitivity and specificity of the average distance for predicting
pregnancy outcomes. P < 0.05 was considered to indicate
statistical significance. All statistical analyses were performed using
IBM SPSS 26.0 (IBM Corp., Armonk, NY, USA).