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, 12.0% of the MNHR population had a history of prior cesarean delivery. Of these women, 2,973 (88.1%) had data available both on mode of delivery of the index pregnancy and the date of their prior delivery. About a fifth of these women (560, 20.1%) delivered by vaginal delivery after cesarean with the remaining 2,233 (79.9%) delivering by repeat cesarean delivery.
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.
Figure 2 illustrates mode of delivery 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).
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 3 shows multivariable modeling of mode of delivery including all variables occurring prior to delivery significant in bivariate comparisons (age, education, parity, BMI, prenatal care attendance, IPI, obstructed labor, hypertensive disease, induction of labor, referred to the facility from another delivery setting, delivery attendant, and delivery in the hospital). The table shows the results of variables significant in the multivariable model as well as IPI, which was not significant (AOR 1.0, CI [1.0,1.0]). Increasing parity and induction of labor (as compared to not being induced) were associated with a reduced odds of repeat cesarean delivery (AOR 0.2, p < 0.05] and AOR 0.1, p < 0.05). Increasing BMI category (AOR 1.4, p < 0.05), experiencing hypertensive disease (AOR 3.5, p < 0.05), and delivering in the hospital (AOR 3223.2, p < 0.05) were associated with an increased risk of repeat cesarean. Delivery provider was dropped from the model as only physicians (compared to non-physicians) performed cesarean delivery.
Table 4 focuses on our objective of understanding how IPI is associated with mode of delivery in varying adjusted models. Compared to an interval of <12 months, if a women has ≥12 months between pregnancies, she is no more likely to experience a repeat cesarean delivery (AOR 1.7, p < 0.05); the results were similar for women waiting ≥24 months (AOR 1.3, p < 0.05). However, for women waiting ≥18 months compared to <18, they were found to have an increased risk of repeat cesarean delivery compared to vaginal delivery after cesarean (AOR 1.4, p < 0.05).
Table 5 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 6 presents the results of individual logistic regressions of the association of repeat cesarean delivery with the outcome of interest (those significant in bivariate comparisons) adjusted for IPI and 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. 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). Results of each regression are presented by showing the independent association of both IPI and mode of delivery. Neither IPI nor mode of delivery was associated with uterotonic use or magnesium sulfate administration. Repeat cesarean delivery reduced the risk of needing a dilation and curettage, but this association did not vary by how IPI was defined (AOR 0.01 – 0.03, p < 0.001).
Table 7 presents the results of individual logistic regressions of the association of repeat cesarean delivery with the 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). Results of each regression are presented by showing the independent association of both IPI and mode of delivery. Regarding breastfeeding, repeat cesarean delivery as compared to vaginal delivery after cesarean significantly reduced the likelihood of a woman breastfeeding within one hour of delivery (AOR 0.009 – 0.10, p < 0.001), but IPI was not associated with the outcome across all definitions, although it nearly increased breastfeeding at intervals over 12 months compared to under a year (AOR 2.0, p = 0.06). Regarding stillbirth, repeat cesarean delivery reduced the likelihood of stillbirth as compared to vaginal delivery (AOR 0.2, p = 0.001 – 0.002), but 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 0.3, p = 0.07).