Background: Cesarean delivery (CD) is the most frequently performed surgical procedure worldwide. Trial of labor after cesarean (TOLAC) is associated with an increase in perinatal complications related to uterine rupture. However, in general, vaginal birth after cesarean (VBAC) is considered safe and women have less morbidity than those who undergo an elective repeat CD. Objective: To develop an integrated model with the best performance criteria for predicting vaginal delivery success after CD. Study design: Retrospective observational study including 2367 women who underwent a TOLAC. A predictive model using classification and regression tree modeling was constructed to predict vaginal delivery using maternal demographic, medical history, and labor predictors. Results: Vaginal delivery was best predicted by spontaneous onset of labor, estimated fetal weight <3775 g, maternal body mass index <25, previous CD as an elective or for fetal distress reasons, and interdelivery interval <2290 days. The algorithm showed a sensitivity of 75%, a specificity of 53%, and the area under the curve was 0.69. Conclusions: The classification and regression tree algorithm can be used to develop a predictive model for the success of TOLAC.

Background and Objectives: Prematurity is currently a serious public health issue worldwide, because of its high associated morbidity and mortality. Optimizing the management of these pregnancies is of high priority to improve perinatal outcomes. One tool frequently used to determine the degree of fetal wellbeing is cardiotocography (CTG). A review of the available literature on fetal heart rate (FHR) monitoring in preterm fetuses shows that studies are scarce, and the evidence thus far is unclear. The lack of reference standards for CTG patterns in preterm fetuses can lead to misinterpretation of the changes observed in electronic fetal monitoring (EFM). The aims of this narrative review were to summarize the most relevant concepts in the field of CTG interpretation in preterm fetuses, and to provide a practical approach that can be useful in clinical practice. Materials and Methods: A MEDLINE search was carried out, and the published articles thus identified were reviewed. Results: Compared to term fetuses, preterm fetuses have a slightly higher baseline FHR. Heart rate is faster in more immature fetuses, and variability is lower and increases in more mature fetuses. Transitory, low-amplitude decelerations are more frequent during the second trimester. Transitory increases in FHR are less frequent and become more frequent and increase in amplitude as gestational age increases. Conclusions: The main characteristics of FHR tracings changes as gestation proceeds, and it is of fundamental importance to be aware of these changes in order to correctly interpret CTG patterns in preterm fetuses.