Fig 1.
Plot of PI (left panel) and the log(PI) (right panel) measured in the uterine artery during the menstrual cycle.
PI, pulsatility index.
Table 1.
Demographic characteristics of the 1668 women included in the study.
Table 2.
Observed and predicted percentiles of the uterine artery pulsatility index on each cycle day.
Fig 2.
Residual plots for the fitted models; from top to bottom and from left to right: boxplot of the standardized residuals, histogram of the standardized residuals, plot of the standardized residuals against the predicted values, and QQ-plot of the studentized residuals.
Panel A employs the entire dataset; Panel B eliminates data from 11 outliers.
Table 3.
Estimates of the regression coefficients and corresponding 95% confidence intervals (CI) of model (1) fitted without the 11 identified outliers.
Fig 3.
(A) Observed (circles) and predicted 5th, 50th, and 95th percentile regression curves for the pulsatility index during the menstrual cycle.
Histogram (B) and boxplot (C) of the expected ovulation date (EOD). For each patient, the EOD was calculated assuming that the luteal phase exhibited a consistent duration of approximately 2 weeks, i.e., E0D = menstrual cycle length—14.
Table 4.
Estimates of the regression coefficients and corresponding 95% confidence intervals (CI) for the model stratified by age and parity.
Fig 4.
Quantile-quantile (Q-Q) plots of the standardized residuals of model (2) for each combination of age and parity groups.
Nulliparous women are presented in the first row, and parous women are presented in the second row. The age group increases from the left to right columns. From left to right and from top to bottom, the Lilliefors-corrected Kolmogorov-Smirnov normality test calculated p-values of 0.738, <0.001, 0.111, 0.954, 0.082, and 0.373, respectively.
Fig 5.
Observed (points) and estimated 5th, 50th, and 95th percentile regression curves of the pulsatility index during the menstrual cycle for each combination of age and parity groups.
Nulliparous and parous women are presented in the first and second rows, respectively. The age group increases from the left to right columns.