Observed and Expected Proportion of Cesarean Deliveries in the Model Validation Group by Decile of Predicted Probability

<p>The white bars indicate the observed proportion and the black bars indicate the expected proportion of cesarean deliveries, based on estimates derived from logistic regression model fitted to the development group. Different graphs represent different procedures for selecting development and validation groups: (A) random selection, (B) selected on hospital throughput, (C) selected on deprivation category (Carstairs score), and (D) selected on year of delivery. Area under the ROC curve for each model is listed in <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0020252#pmed-0020252-t003" target="_blank">Table 3</a>.</p

Use of ALLRs to Predict Probability of Cesarean Section among Women Delivered 37 to 39 wk with a Documented Duration of Labor of Greater than or Equal to 4 h

<p>Probability estimated using likelihood ratios in <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0020252#pmed-0020252-t004" target="_blank">Table 4</a> (excluding gestational age) and the prior odds of 0.22 (equivalent to background risk of cesarean section in this group).</p

Proportion of Uterine Ruptures in Relation to the Quintile of Predicted Probability of Emergency Cesarean Delivery for the Whole Population

<p><i>n</i> = 23,286; <i>p</i> < 0.001 (Chi square test for trend).</p

Stratified Analysis of Maternal Age and Risk of Cesarean Section

<p>Adjusted odds ratio for a 5-y increase in maternal age (bars are 95% CIs) stratified by maternal age, year of delivery, week of gestation, and deprivation category. Interactions were statistically significant for year of delivery (<i>p</i> < 0.001), week of gestation (<i>p</i> = 0.002), and deprivation category (<i>p</i> = 0.002) using the likelihood ratio test. Odds ratios are adjusted for maternal age, height, deprivation category, onset of labor, week of gestation, sex, birth weight percentile of infant, and year. The vertical dashed line indicates unity.</p

Maternal Age and the Risk of Cesarean Delivery

<p>Proportion of women being delivered by emergency intrapartum cesarean section in relation to age of mother (<i>n</i> = 583,847). Bars are binomial 95% CIs.</p

Myometrial Contractility in Relation to Maternal Age

<div><p>(A) Trace of isometric tension from myometrial strip obtained from a 40-y-old woman being delivered by planned cesarean section. The blue line represents the 15 min before addition of potassium, and the red line 7 min in the presence of 50 mM of potassium. The area under the curve is the space between the tension trace and the baseline, indicated by the blue and red lines. The log₁₀ of the ratio of these two areas is the contraction unit. The spontaneous contraction before the addition of potassium and the contraction following potassium being washed out are both multiphasic.</p> <p>(B) Mean spontaneous contractile activity (quantified as contraction units) of isolated strips of myometrium obtained from women (<i>n</i> = 62) at the time of planned cesarean section in relation to the age of the donor. Regression line: <i>y</i> = 0.1078 + (−0.0174 × age); 95% CI for slope, −0.0326 to −0.0022.</p> <p>(C) Proportion of spontaneous contractions that were multiphasic in relation to maternal age (<i>n</i> = 62, 181 samples). See text for regression analysis of (B) and (C).</p></div

Time Trends in Maternal Age Distribution and Cesarean Section Rates in Scotland between 1980 and 2005

<div><p>(A) Proportion of women per year delivering within the age ranges 30–34, 35–39, and ≥40 y.</p> <p>(B) Proportion of women per year delivered by emergency cesarean section.</p></div

Maternal Age and the Duration of Labor and Risk of Operative Vaginal Birth

<div><p>(A) Mean duration of spontaneous labor in relation to maternal age (<i>n</i> = 409,703). Bars are 95% CIs of the mean.</p> <p>(B) Proportion of nulliparous women who required operative vaginal delivery in relation to maternal age among the 518,787 women delivered by a means other than emergency cesarean section. Bars are binomial 95% CIs.</p></div