Statistical analysis
Continuous baseline characteristics
were
represented as mean ± standard deviation (SD) or the median and range,
depending on their distribution. Categorical variables were represented
as frequency with percentages. The differences about baseline
characteristics and pregnancy outcomes between subgroups were compared
using the independent-samples t test for continuous variables or
Chi-square test for categorical variables. A binary logistic regression
was performed to evaluate the associations between LMs with different
causes and subsequent pregnancy outcomes, including early miscarriage
rate (EMR), late miscarriage rate (LMR), preterm birth rate (PBR) and
live birth rate (LBR). Potential confounders were also adjusted, which
included maternal age, body mass index (BMI), basal FSH level, number of
bilateral basal follicles, PCOS, prior early spontaneous miscarriage,
prior live birth, controlled ovarian hyperstimulation (COH) protocol,
endometrial thickness on hCG trigger day. LMs, controlled ovarian
hyperstimulation (COH) protocol, and endometrial thickness on hCG
trigger day were considered as multi-categorical variables, and
transformed into dummy variables. The associations were presented as an
adjusted OR (aOR) with a 95% CI.
P values were given for two-sided tests and statistical significance was
defined by P < 0.05. All of the statistical analyses were
performed using SPSS version 26.0 (Chicago, IL, USA).