Figure 1 is a flow diagram of the population of women included in this study. Between January 2017 and April 2020, 26,465 women delivered in the Guatemalan clusters of the MNHR. 3,170 women, which is 12.0% of the MNHR population, had a history of prior cesarean birth. Of these women, 2,973 (88.1%) had data available both on mode of birth of the index pregnancy as well as the date of their prior birth, which we used to calculate IPI. About a fifth of these women (560, 20.1%) delivered by vaginal birth after cesarean with the remaining 2,233 (79.9%) delivering by repeat cesarean delivery.
Figure 2 illustrates mode of birth among women with a history of prior cesarean delivery as a function of IPI (time since a woman’s last delivery). A univariate logistic regression of IPI (categorical variable of 6-month intervals) on mode of delivery found that with each successive 6-month interval, repeat cesarean delivery became 20% more likely (UOR 1.2, p < 0.001).
Table 1 presents the sociodemographic and obstetric/labor characteristics of the population overall and by mode of delivery. The population was overall median age 27 with interquartile range (IQR) 23 to 31 years. Most women had some schooling (93.5%), just over half were primiparous (52.7%), and almost two-thirds women (73.1%) were of normal or overweight body mass index (BMI). Women who delivered by repeat cesarean delivery (as compared to vaginal delivery after cesarean) were statistically more likely to be younger (median age 27 versus 28), to have had schooling (95.2% versus 86.8%), to be less parous (parity 3+ 11.6% versus 44.8%), and more likely to be overweight or obese (71.0% versus 61.2%), p < 0.001.
Regarding obstetric and labor characteristics (Table 1) overall women had an IPI of 27 months (IQR 15 to 46 months), most had antenatal care (97.0%) and singleton gestations (99.0%), birthweight of their babies was median 2870 grams (IQR 2610 to 3120 grams) of mostly term infants (93.4%). Only 1.6% of the population was induced and a majority were delivered by obstetricians (83.0%) in the hospital setting (81.3%). When comparing women who delivered by repeat cesarean delivery compared to vaginal delivery after cesarean, they differed significantly on IPI (29 months versus almost 22 months), antenatal care (98.3% versus 91.4%), women experiencing obstructed labor (4.5% versus 2.3%) and induction of labor (1.0% versus 3.9%), hypertensive disease (7.1% versus 1.1%), and referral in labor (19.2% versus 10.0%), p < 0.05. Women delivered by repeat cesarean delivery were more likely to be delivered by an obstetrician (96.9% versus 27.3%) and in the hospital (93.0% versus 34.8%), p < 0.001.
Table 2 shows multivariable modeling of repeat cesarean birth including all variables occurring prior to delivery significant in bivariate comparisons (age, education, parity, BMI, prenatal care attendance, obstructed labor, hypertensive disease, induction of labor, and referred to the facility from another delivery setting. The table shows the results of variables significant in the multivariable model as well as IPI, which was included in the model first as a continuous variable (column 1) and subsequently as a dichotomous variable defined by 12, 18, and 24 months. Increasing education, BMI, receipt of antenatal care, obstructed labor and hypertensive disease were associated with an increased odds of repeat cesarean delivery across all interpregnancy intervals, p < 0.05). Increasing parity and induction of labor were associated with a reduced risk of repeat cesarean, p < 0.05. Delivery provider and delivery location were dropped from the model as only physicians (compared to non-physicians) performed cesarean delivery and cesarean births only occur in an operating room in this region; including these covariates in the model prevented in from converging.
Table 3 shows the results of bivariate comparisons of maternal and perinatal/neonatal outcomes by mode of delivery. In the overall population most maternal outcomes were rare (< 2.0%), but 5.2% of women in the cohort were treated with magnesium sulfate for seizure prophylaxis and many women were treated with uterotonics (86.5%). In bivariate comparisons, women varied by mode of delivery on uterotonic receipt (98.2% of repeat cesareans versus 40.0% of vaginal deliveries after cesarean) and dilation and curettage (0.1% of cesareans versus 3.2% of vaginal deliveries). With respect to neonatal outcomes, most babies were born alive (97.8%), 21.1% were breastfed within an hour of delivery, 4.1% of infants required neonatal antibiotics, and the remainder of adverse outcomes occurred rarely at less than a 2% prevalence. In bivariate comparisons, fetal status at delivery varied by mode of delivery (stillbirths in 1% of cesareans versus 3.9% of vaginal deliveries), as did breastfeeding within one hour of delivery (6.1% of cesareans versus 82.9% of vaginal deliveries), p < 0.001.
Table 4 presents the results of individual logistic regressions of the association of repeat cesarean delivery with the maternal outcomes of interest (those significant in bivariate comparisons) adjusted for covariates significant in bivariate comparisons. Maternal outcomes that varied by mode of delivery were uterotonic use, performance of dilation and curettage, and administration of magnesium sulfate. The likelihood of the outcomes by varying IPI definitions are shown. Each logistic regression was performed first with IPI as a continuous variable and then as a dichotomous variable (set at 12 months, 18 months, and 24 months). The likelihood of the outcomes did not vary with IPI definition.
Table 5 presents the results of individual logistic regressions of the association of repeat cesarean delivery with the neonatal outcome of interest (those significant in bivariate comparisons) adjusted for IPI and covariates significant in bivariate comparisons. Perinatal outcomes that varied by mode of delivery were breastfeeding within one hour and fetal status at delivery. Each logistic regression was performed first with IPI as a continuous variable and then as a dichotomous variable (set at 12 months, 18 months, and 24 months). The likelihood of the outcomes did not vary with IPI definition. Regarding stillbirth, IPI was not associated with the outcome across all definitions, although it marginally (but not statistically) reduced stillbirth at intervals of greater than compared to less than 12 months (AOR 0.5 95% CI [0.2,1.1], p = 0.08).