Journal of Pregnancy and Child Health
Open Access

For women who have undergone a previous cesarean delivery, optimal management of subsequent deliveries is recurrently debated. The two options are Trial of Labor after Cesarean Delivery (TOLAC) and Planned Repeat Cesarean Delivery (PRCD) [1]. Failed trial of labor and uterine rupture, an infrequent but serious complication, in women who attempt TOLAC are the two main issues [2]. Despite these risks, it should be noted that a successful and uncomplicated TOLAC has numerous short and long-term benefits [2]. A consensus involving the National Institute for Health and Care Excellence (NICE), the Royal College of Obstetricians and Gynecologists (RCOG),and American College of Obstetricians and Gynecologists (ACOG)/National Institutes of Health (NIH) defined that TOLAC is clinically safe for most women with a single previous cesarean delivery [3]. This strategy also limits an increase in the rate of birth by cesarean delivery and associated maternal morbidity [4-8].

There has been a continuing debate on the definition of an acceptable cesarean delivery rate that achieves the best maternal and neonatal outcomes. There are limitations of the available evidence as no large randomized trials have been conducted that provide comparative data on the maternal and neonatal outcome between TOLAC and PRCD in women with previous cesarean delivery [9,10]. The best method of cervical ripening and/or labor induction in this population has also not been established [11].

The probability of success of an TOLAC is greater if the woman presents with a previous vaginal delivery and a favorable cervix [12]. When the probability of success is high, TOLAC is more effective and less expensive than an elective cesarean [13]. The cost-benefit ratio improves in pregnant women with multiple subsequent vaginal deliveries [14]. The medical and obstetric benefits of a successful TOLAC derive from the avoidance of the risks associated with an iterative cesarean. Newborns from iterative elective cesarean have significantly higher rates of respiratory mobility and hospitalization in the Neonatal Intensive Care Unit as well as longer length of stay when compared to those vaginally delivered [15]. Most maternal morbidity associated with TOLAC occurs when cesarean delivery becomes necessary. On the other hand, the medical and obstetric benefits of elective cesarean result from the avoidance of risks associated with TOLAC, especially uterine rupture. Thus, the benefits of TOLAC are closely related to successful vaginal delivery, which has the lowest morbidity [1]. A failed TOLAC has greater morbidity than a elective cesarean [16].

The planning of the birth route should be addressed early in the pregnancy follow-up and may even begin in the pre-conception. The decision should be an integrative process between pregnant women and their physicians taking into account the best available clinical evidence [17-20]. The ideal candidates for TOLAC are women with a high probability of vaginal delivery and a very low probability of intrapartum rupture of the uterus. The scarcity of definitive data predicting these results makes the selection of the ideal candidates a clinical challenge [1].

Our aim was to study the factors of good and bad prognosis for vaginal delivery in all women with previous cesarean who went into spontaneous labor or underwent induction of labor at our center between January 2015 and December 2016.

A retrospective cohort was conducted with a consecutive sample of 374 pregnant women with cephalic singletons gestations with a single previous CS between January 2015 and December 2016.

Collected variables included maternal age and body mass index, co-morbidities (diabetes, hypertension), obstetrical history (previous vaginal delivery and previous cesarean motives), bishop score, onset of labor (spontaneous or induced), oxytocic acceleration, gestational age and newborn characteristics as (sex, birthweight).

The measure of association between vaginal delivery and each potential prognostic factors was analyzed through Odds Ratio (OR), with 95% Confidence Intervals (CI). Univariate and multivariate conditional logistic regression models were constructed. Statistical analysis was performed using IBM corp. Released 2016. IBM SPSS Statistics for Macintosh, version 24.0. Armonk, NY: IBM Corp.

We included 374 patients. The average age was 34.0 years with a SD (Standard Deviation) of 4.0 years with a average gestational age of 39.2 weeks with a standard deviation of 1.5 weeks. The rate of cesarean section in our sample was 39.7% (Table 1).

Table 1: Successful vaginal delivery analysis by determinant.

Table 1 illustrates the statistical results for the various prognostic factors considered for vaginal delivery. The variables that potentially influence the way of delivery in women with previous cesarean are: Height, previous vaginal delivery, Bishop score at admission, onset of labor, gestational age, newborn weight and the previous cesarean motives (cephalopelvic disproportion and fetal malpresentation).

We did not find a statistically significant association between maternal age (OR=1.1, CI 95%=0.7-1.7, p>0.05), BMI (Body Mass Index) (OR=1.4, CI 95%=0.8-2.3, p>0.05), diabetes (OR=1.1, CI 95%=0.6-2.1, p>0.05) and oxytocic acceleration (OR=0.7, CI 95%=0.5- 1.2, p>0.05) and the way of delivery. In the previous cesarean motives group, also for a 5 per cent significance level, was not find a statistically significant association between arrest of labor (OR=1.1, CI 95%=0.7- 1.8, p>0.05) and non-reassuring fetal status (OR=0.9, CI 95%=0.5-1.5, p>0.05) and the way of delivery.

Patients with >163 cm were found to be more likely to have a vaginal delivery ( OR=1.9, CI 95%=1.2-3, p<0.05 ) compared to those with <163 cm. We also found that women with a prior vaginal delivery were more likely (OR=4.1, CI 95%=1.4-12.1, p<0.05) to have a vaginal delivery in the current pregnancy.

Spontaneous onset of labor (OR=3.5, IC 95%=2.2-5.5, p<0.05) increase the likelihood of a vaginal delivery, the same being true to women with a ≥ 6 Bishop score at admission ( OR=0.5, CI 95%=0.2-0.7, p<0.05 ).

A gestational age ≤ 39 weeks (OR=2.1, CI 95%=1.4-3.2, p<0.05) and a newborn weight <3500 g (OR=2.4, CI 95%=1.5-3.8, p<0.05) are more likely to end in a vaginal delivery.

After analyzing certain previous cesarean motives, it was concluded that fetal malpresentation as a previous reason is a good prognostic factor (OR=2.6, CI 95%=1.3-5.0, p<0.05) for vaginal delivery. In the other hand, cephalopelvic disproportion as a previous cesarean reason (OR=0.3, CI 95%=0.2-0.6, p<0.05) have a lower probability of vaginal delivery in the current pregnancy.

Among several potential prognostic factors that showed significant association with a vaginal delivery by calculating the odds ratio, four of them remained independently associated with a vaginal delivery when we carried out the regression analysis. In the final logistic regression model, the height (adjusted OR=2,6, CI 95%=1.5-4.5, p<0.05), onset of labor (adjusted OR=4.2, 95% CI=2.2-7.7, p<0.01), gestational age (adjusted OR=2.4, 95% CI=1.4-4.1, p<0.01) and the newborn weight (adjusted OR=11.0, 95% CI = 2.7-45.9, p <0.01) proved to be a significant prognostic factor for vaginal delivery.

Although observational studies have consistently reported that a TOLAC is less likely to result in vaginal delivery in obese pregnant women and in our study there is a trend towards a higher percentage of cesareans in these group, a statistically significant association was not found [22]. On the other hand, we found a statistically significant relationship with height, one of BMI parameters. This is in agreement with the data available in the literature, in which maternal height interacts with birth weight and predicts the likelihood of an emergency cesarean [23]. Despite having smaller neonates, shorter mothers are also at a higher risk for obstructed labor, resulting in an assisted delivery, in particular emergency cesarean [23]. Obstructed labor is related to the narrower pelvises of shorter women, through which the delivery of head or shoulders of the baby is hindered [23].

Rates of successful TOLAC in women with gestational and pregestational diabetes appear to be lower compared with nondiabetic women undergoing TOLAC [24-26]. In the present study this relationship was not found. This may be the result of the small sample of patients with diabetes or the therapy (including adherence) of these patients, which may confound these results, although the present data does not allow for a more rigorous comparison.

It is well established that women with a successful vaginal delivery before or after their primary cesarean delivery are significantly more likely to have a successful TOLAC than those who have never delivered vaginally [27]. In addition, some studies report that women with a previous vaginal delivery have a lower risk of uterine rupture during TOLAC compared with women without prior vaginal delivery [28]. The subset of women in our study with a previous vaginal delivery is relatively small, but nonetheless a relationship between a previous vaginal delivery and TOLAC can be demonstrated.

When admitted to the labor unit, women in spontaneous labor or with >4 cm cervical dilation are more likely to have successful TOLAC [27,29]. Similar conclusions can be taken in our study, where women admitted with a spontaneous labor or with a Bishop Score ≥ 6 are more likely to have a vaginal delivery. Both determinants demonstrated a statistically significant relationship with a vaginal delivery.

It has been consistently observed that women who attempt TOLAC beyond 40 weeks of gestation are less likely to successfully deliver vaginally [30,31]. Labor with less than 40 weeks is intimately related with smaller newborns and spontaneous onsets, two good prognostic factors for vaginal delivery. In our study, women admitted with ≤ 39 weeks were more likely to have a vaginal delivery, probably for these reasons.

For women with no previous vaginal delivery, the likelihood of successful TOLAC falls to ≤ 50 percent when birth weight increases above 4000 g. Also of bad prognosis was the use of medical induction or augmentation of labor attempting TOLAC [1]. Our study showed that women with <3500 g newborns are more likely to have a vaginal delivery. Literature are not consensual in offering elective cesarean to women with suspected fetal macrosomia [32].

Success rates for vaginal delivery are lower if the indication for the previous cesarean was cephalopelvic disproportion, being well described in the literature [32,33]. Our results are consistent with this observation. On the other and, when the previous cesarean indication was fetal malpresentation, the probability of vaginal delivery is higher compared with the other motives. This is probably related to the fact that women with pelvis suitable for vaginal delivery are submitted to elective cesarean due to the fetal malpresentation.

Maternal height, onset of labor, gestational age and newborn weight appear to be independent factors, prognostic for successful vaginal delivery. More studies analyzing these and other variables will be important in order to better understand their significance and importance. In the case of a term pregnancy with characteristics that imply a low probability of a successful vaginal delivery, the decision on a labor test, with the risks associated with it, must be considered on a case-by-case basis. Although vaginal delivery in women submitted to a previous CS is generally safe, a better definition of the characteristics inherent to each pregnancy is required, which could better anticipate the success rate, but more importantly, the risk of complications.