Statistical Analyses
The sample size was calculated based on a study by Di Spiezio Sardo et al. (2017) titled Risk of Cesarean Scar Defect Following Single- vs Double-Layer Uterine Closure: Systematic Review and Meta-Analysis of Randomized Controlled Trials.10 Their study revealed niche formation rates for single- and double-layer closure types of 25% and 43%, respectively. Based on tools available at the Power and Sample Size website (http://powerandsamplesize.com/Calculators), needed sample size was calculated at 141 for each treatment group with 90% power and 0.05 alpha error.
All data were statistically analyzed using the IBM SPSS 21.0 software. Categorical measurements were presented as frequencies and percentages, while continuous measurements were summarized as means and standard deviations (median and range when needed). Distributions were checked and the student’s t-test was used for variables meeting the parametric test assumptions when comparing the continuous measurements based on groups, while the Mann Whitney U test was used for those that did not meet the parametric test assumptions. Finally, chi-squared or Fisher’s test statistics were used to compare categorical variables. Statistical significance was set to 0.05 for all tests.