Trial of labor following cesarean in preterm deliveries: success rates and maternal &amp; neonatal outcomes- a multicenter retrospective study

doi:10.21203/rs.3.rs-1537837/v1

Purpose: To evaluate rates of vaginal birth after cesarean (VBAC) among parturients attempting preterm trial of labor following a cesarean delivery (TOLAC) vs. term TOLAC.

Methods: A multicenter historic cohort study at two university-affiliated centers between August 2005 and March 2021. Parturients in their 2^nd delivery, attempting TOLAC after a single low segment transverse cesarean delivery (CD) were included.

We retrospectively examined computerized medical records of all preterm (<37 weeks) and term (37-42 weeks) births. Multifetal gestations and post-term deliveries (≥42 weeks) were excluded. A univariate analysis was conducted followed by a multivariate analysis.

Results: 4,865 second deliveries following previous CD were identified; 212 (4.4%) preterm and 4653 (95.6%) term. Hypertensive disorders, diabetes and fertility treatments were significantly more prevalent in the preterm group. VBAC rate was significantly lower in preterm group (57.5% vs 79.7%., p<0.01), including both spontaneous and vaginal-assisted deliveries. In multivariate analysis, preterm TOLAC was independently associated with TOLAC failure [adjusted odds ratio (aOR) 2.24, [95% confidence interval (CI) 1.62-3.09]. Overall, maternal outcomes were favorable. Rates of uterine rupture, re-laparotomy and post-partum hemorrhage were comparable between groups. Neonatal outcomes were less favorable among the preterm group, however, preterm vs. term TOLAC was not associated with low 5-minute Apgar score (aOR 1.76, 95% CI 0.92-3.40).

Conclusion: In our study, VBAC rates were lower in preterm compared to term deliveries. Maternal outcomes were comparable. Neonatal outcomes were less favorable in the preterm group, more likely due to prematurity than delivery mode.

Trial of labor after cesarean (TOLAC)

vaginal birth after cesarean (VBAC)

preterm delivery

Caesarean section is the most performed surgery in modern obstetrics. The rates of caesarean section (CS) have increased worldwide over the last few decades¹ to the extent that was labeled as an epidemic by the International Federation of Gynecology and Obstetrics (FIGO)². Repeat cesarean births account for a high percentage of the total number of caesarean sections.¹ As with any surgery, CS is associated with short and long term risks. However, in women with repeat cesarean delivery, the risks of maternal complications such as the need for blood transfusion, bowel and bladder injury, placenta previa, accrete, uterine rupture and incurred complications are elevated. ^{3, 4}

Trial of labor after cesarean (TOLAC) can be a safe alternative for RCD (repeated cesarean delivery).⁵ Short term advantages of vaginal birth after CD (VBAC) include avoiding major surgery, lower risk of hemorrhage and infection, and shorter recovery periods. Because most maternal morbidity during TOLAC occurs when repeat cesarean delivery becomes necessary, VBAC is associated with fewer complications than elective repeat cesarean delivery, and failed TOLAC is associated with serious maternal and neonatal complications.⁶.

The literature includes numerous studies and discussions as to who is the optimal candidate for successful TOLAC^{7, 8, 9}. TOLAC studies usually exclude preterm delivery primarily due to the complexity in establishing whether neonatal morbidity relates to the TOLAC attempt, to neonatal prematurity, or to dysfunctional preterm labor and its associated complications. ^{7, 16} As a result, data evaluating TOLAC in preterm births is scarce. Preterm birth, defined as birth before 37 completed weeks of gestation, complicates 12% of deliveries in the U.S and accounts for 75% of perinatal mortality and more than half the long-term morbidity.^{10, 11} Spontaneous preterm parturitions may be triggered by multiple possible reasons, including: infection or inflammation, uteroplacental disorders, uterine overdistension, stress, and other immunologically mediated processes.¹² The optimal mode of delivery for preterm labor is controversial. Those supporting elective preterm CD maintain that CD reduces the chances of fetal or neonatal death and birth trauma. Counter claims profess that such policy leads to unnecessary risk for both parturients and neonates. ^{13, 14, 15}

The purpose of the current analysis is to compare VBAC success rates and maternal and neonatal morbidity in preterm versus term parturients attempting trial of labor (TOL) following a single CD.

We conducted a multicenter retrospective cohort study using computerized medical records of two university-affiliated medical centers in Jerusalem, Israel: Shaare Zedek Medical Center (SZMC) and Bikur Holim Medical Center (BHMC), between August 2005 and March 2021. Together these medical centers account for approximately 16% of all deliveries in the state of Israel, with a mean annual volume of 20,000 births.

We enrolled parturients in their second delivery, attempting TOL following a single low segment CD between 24 and 42 weeks of gestations. Excluded from the study were parturients with non-vertex presentation, multifetal gestation, fetal demise, pre-viable (< 24 + 0 week) and post-term deliveries (≥ 42 + 0 weeks). A comparison was made between those who attempted TOLAC prior to 37 + 0 weeks of gestation (preterm), and those attempting TOLAC between 37 + 0 to 42 + 0 weeks of gestation (term).

SZMC and BHMC share similar departmental protocols consistent with the criteria defined in the TOLAC guidelines of the Israeli committee of Obstetrics and Gynecology. Accordingly, TOLAC is offered to a parturient with a prior history of a single low segment CD. All women who met criteria were provided with comprehensive information about the risks and benefits of both TOLAC and alternative repeat CS. Upon receipt of informed consent, the patient was approved TOLAC. In both medical centers, all TOLAC deliveries are managed by resident physicians and supervised by a board-certified obstetrician who is responsible for all real-time decisions regarding induction of labor, labor augmentation, operative vaginal deliveries and emergency CDs. Continuous electronic fetal monitoring is mandatory. Vaginal births are delivered by certified nurse midwives.

Parturients with a history of one previous CD requiring induction of labour are induced using a double lumen balloon, amniotomy, or low dose oxytocin (oxytocin 10 IU in 1000ml Ringer’s lactate, starting at 0.5 mU/min and rising 0.5 mU/min every 20 minutes until achieving 3–4 contractions per 10 minutes). Prostaglandin post CD are not used.

The SZMC and BH medical record databases are electronic, in which all labor and deliveries are updated during labor and delivery by attending healthcare professionals. All data is audited periodically by trained technical personnel to ensure the validity of the data, which eliminates information bias. Maternal and neonatal records were reviewed and retrieved for relevant data, information was coded and identifiable, and personal information for each patient was protected by anonymization prior to analysis. The study was approved by the local institutional ethics committee in accordance with the principles of the Declaration of Helsinki (IRB: 0411-21-SZMC).

Primary outcome was defined as success rates of vaginal delivery (VD) in each of the study groups.

Secondary outcomes were defined as a composite of adverse maternal outcomes involving one or more of the following: Postpartum Hemorrhage (PPH), hemoglobin drop ≥ 4 gr/dL, blood products transfusion, maternal intensive care unit (ICU) admission.

The terms used were defined as the following: Uterine rupture - complete uterine scar rupture, i.e. involving the occurrence of a full-thickness defect with direct connection between peritoneal space and the uterine cavity. Diagnosis was made by the attending physician in the course of an explorative laparotomy. Re-laparotomy – additional abdominal operation performed during hospitalization for delivery¹⁷ PPH estimation can be evaluated either objectively or subjectively. A subjective evaluation is when estimated blood loss is over 1000 ml in VD or CD ¹⁸ (pads are weighted following VD, but in some cases when it is not feasible to weigh pads, and blood loss is estimated subjectively by the midwife/obstetrician); The empirical PPH definition is when the parturient receives transfusion of blood products and/or hemoglobin drop ≥ 3 gr/dL¹⁸.

Statistical analysis was performed using the SPSS package (version 23 statistical package; IBM. Armonk, NY). An initial univariate analysis was followed by a multiple regression model. Categorical variables were compared using Chi square and Fisher's exact test when appropriate. Continuous variables presentation is according to each variable distribution, while normal distributed variables presented as a mean and standard deviation and compared using Student's t-test. Those displaying non-normal distribution are presented as median with interquartile range and compared using Mann Whitney test. All analyses were two sided and a p value < 0.05 was considered statistically significant.

During the study period, 4,865 deliveries fulfilling inclusion criteria were identified, of which 212 (4.4%) parturients attempted preterm TOLAC and the remaining 4,653 (95.6%) attempted term TOLAC (Fig. 1).

Table 1 presents the general demographics and obstetrical characteristics of both study groups. Parturients in the preterm TOLAC group were significantly older than those in the term TOLAC group. Rates of recurrent pregnancy loss, fertility treatments, hypertensive and diabetic (pre-gestational and gestational) disorders of pregnancy were all higher in the preterm TOLAC group. Indication for previous CD did not differ significantly between the groups, in both groups the most common indication was none reassuring fetal heart rate.

Table 1

General demographics characteristics of both study groups
	Preterm TOLAC = 212	Term = 4653	P value
Maternal age (Mean ± SD)	28.9 ± 8.4	27.5 ± 4.5	< 0.01
Gravidity (Median, IQR)	2 (1–3)	2 (1–4)	0.26
Recurrent miscarriage (≥ 3)	9 (4.2%)	78 (1.7%)	0.01
Fertility treatment n (%)	21 (9.9%)	289 (6.2%)	0.03
Diabetes mellitus*,n (%)	19 (9.0%)	219 (4.7%)	< 0.01
Gestational hypertensive disorders of pregnancy** n (%)	21 (9.9%)	101 (2.2%)	< 0.01
Indication for previous Cesarean delivery:
Arrest of decent, n (%)	3 (1.4%)	53 (1.1%)	0.56
None-reassuring fetal heart rate, n (%)	140 (66.0%)	3,024 (65%)	0.42
Mal-presentation, n (%)	10 (4.7%)	184 (3.9%)	0.51
Other, n (%)	59 (27.9%)	1392 (30.0%)	0.28
TOLAC – Trail of labor after cesarean (pre gestational + gestational) *Hypertensive disorders of pregnancy, a composite of: gestational hypertension, preeclampsia and eclampsia.

Table 2 displays index delivery characteristics and maternal outcomes.

Table 2

Index delivery characteristics and maternal outcomes
	Preterm TOLAC = 212	Term = 4653	P value
Gestational age at delivery (Median, IQR)	34 (32–37)	39 (38–41)	< 0.01
Spontaneous onset of labor n (%)	121 (57.1%)	2193 (47.1%)	0.84
Induction of labor n (%)	18 (8.5%)	483 (10.4%)	0.38
Augmentation of labor n (%)	73 (34.4%)	1977 (42.5%)	0.02
Meconium stained amniotic fluid n (%)	9 (4.2%)	919 (19.8%)	< 0.01
Persistent occiput posterior n (%)	6 (3.3%)	193 (4.6%)	0.41
Epidural n (%)	87 (41%)	3324 (71.4%)	< 0.01
Spontaneous vaginal delivery n (%)	103 (48.5%)	2829 (60.6%)	< 0.01
Instrumental delivery n (%)	19 (9.0%)	890 (19.1%)	< 0.01
In labor cesarean n (%)	90 (42.5%)	943 (20.3%)	< 0.01
Composite adverse maternal complication n (%)	41 (19.3%)	996 (21.4%)	0.47
Dehiscence of uterine scar n (%)	2 (0.9%)	29 (0.6%)	0.57
Uterine rupture n (%)	1 (0.5%)	29 (0.6%)	0.78
Hysterectomy n (%)	1 (0.5%)	2 (0.0%)	0.01
Re-laprotomy n (%)	0 (0%)	2 (0%)	0.76
PPH n (%)	39 (18.4%)	976 (21%)	0.37
Hemoglobin drop > 4 gr/dL n (%)	19 (9%)	441 (9.6%)	0.78
Blood products infusion n (%)	14 (6.6%)	143 (3.1%)	< 0.01
Endometritis n (%)	3 (1.4%)	202 (4.3%)	0.04
ICU admission n (%)	1 (0.5%)	1 (0%)	< 0.01
TOLAC – Trail of labor after cesarean, IQR- interquartile range, PPH – postpartum hemorrhage, ICU intensive care unit; IV- intra venous. Maternal composite outcome was defined as one or more of the following: PPH, hemoglobin drop > 4 gr/dL, blood products infusion, ICU admission.

Median gestational age at delivery among preterm TOLAC was 34 weeks versus 39 weeks among term TOLAC. Rates of spontaneous onset of labor and induction of labor did not differ significantly between the groups, however, rates of labor augmentation were significantly lower in preterm TOLAC. Epidural usage during delivery as well as meconium-stained amniotic fluid were both significantly less common in preterm TOLAC.

The rates of spontaneous vaginal deliveries were significantly lower in preterm TOLAC group (48.5% vs 60.6%, p < 0.01), as were the rates of instrumental deliveries (9.0% vs. 19.1%, p < 0.01). Consistent with the above results, the rates of in-labor CD were higher in preterm TOLAC (42.5% vs 20.3%, p < 0.01).

Overall, composite adverse maternal outcomes did not differ between the groups, nonetheless, rates of blood products administered, and maternal ICU admissions were significantly higher among preterm TOLAC (6.6% vs. 3.1% and 0.5% vs 0.0%, respectively, p < 0.01 for both). Rates of uterine rupture/dehiscence and re-laparotomy were comparable between the groups. There were 3 cases that resulted in hysterectomy: one in the preterm group and two in the term group. In the preterm group, placenta accrete was identified during surgery with uncontrollable hemorrhage and resulted in a cesarean hysterectomy. In the term group, both hysterectomy cases were post-partum due to intractable bleeding and disseminated coagulopathy attributed to uterine atony. In both cases, several attempts were made for uterine preservation, including B-lynch and angiography, but unfortunately, both cases resulted in hysterectomy.

Using multiple regression logistic model adjusting for: epidural analgesia, oxytocin augmentation, diabetes and hypertensive disorders of pregnancy, preterm versus. term TOLAC was found independently associated with in-labor cesarean (aOR 2.24, 95% CI 1.62–3.09. Oxytocin augmentation, diabetes, and hypertensive disorders of pregnancy were all found as risk factors for in-labor cesarean, while epidural anesthesia was related to higher VBAC success.

Table 3 presents neonatal outcomes of both study groups. As anticipate, neonatal birth weight was significantly lower in the preterm TOLAC group. Rates of Apgar score < 7 in 1- and 5-minutes following delivery, rates of neonatal intensive care unit admission (NICU), and transient tachypnea of the newborn were all significantly higher in the preterm TOLAC group. In a multiple regression logistic model, controlling for small for gestational age and in-labor cesarean, preterm TOLAC was not independently found to be associated with 5 minutes Apgar < 7 (aOR 1.76, 95% CI 0.92–3.40).

Table 3

Neonatal outcomes of both study groups of both study groups
	Preterm TOLAC = 212	Term = 4653	P value
Gestational weight (Mean ± SD)	2277.5 ± 732.8	3296.8 ± 428.3	< 0.01
Gender, male n (%)	126 (59.4%)	2336 (50.2%)	0.01
Apgar 1 < 7 n (%)	38 (17.9%)	273 (5.9%)	< 0.01
Apgar 5 < 7 n (%)	22 (10.4%)	60 (1.3%)	< 0.01
Meconium aspiration n (%)	0.0 (0.0%)	11 (0.2%)	0.48
NICU admission n (%)	116 (54.7%)	170 (3.7%)	< 0.01
TTN n (%)	37 (17.5%)	66 (1.4%)	< 0.01
Mechanical ventilation n (%)	46 (21.7%)	46 (1%)	< 0.01
HIE n (%)	0 (0.0%)	9 (0.2%)	0.52
TOLAC – Trail of labor after cesarean Composite adverse neonatal outcome was defined as one of the following: 5-min Apgar score ≤ 7, neonatal asphyxia, neonatal intensive care unit (NICU) admission, and the need for mechanical ventilation. TTN – transient tachypnea of the newborn, HIE – hypoxic ischemic encephalopathy.

Table 4

Multivariate logistic regression analysis for the association between preterm TOLAC and in-labor cesarean
	p value	aOR	95%CI
Preterm TOLAC	< 0.01	2.24	1.63	3.09
Oxytocin augmentation of labor	< 0.01	5.09	4.30	6.03
Epidural analgesia	< 0.01	0.21	0.17	0.24
Diabetes (pre-gestational + gestational)	< 0.01	1.71	1.25	2.33
Hypertensive disorders of pregnancy	< 0.01	2.70	1.79	4.06
TOLAC – trial of labor after cesarean, CI - Confidence Interval, aOR -adjusted odds ratio,

This multicenter tudy compared maternal and neonatal outcomes in parturients who attempted preterm TOLAC to term TOLAC. Despite the increased risk for in labor CD in the preterm group, overall maternal outcomes were comparable and favorable. Neonatal outcomes were generally less favorable among the preterm group, as expected. However, the 5-minute Apgar score was not independently associated with preterm TOLAC. VBAC rates in this study were significantly lower in preterm TOLAC, 57%; compared with 80% in the term TOLAC. Previous studies have described equivalent ¹⁹ or higher²⁰ VBAC rates in preterm TOLAC (72–82%) compared to term TOLAC. Factors such as, diabetes mellitus and hypertensive disorders of pregnancy ^{21, 22, 23} previously linked to VBAC failures were significantly more prevalent among preterm TOLAC parturients in this study. Performing a multivariate logistic regression, both above-mentioned factors were found independently associated with in-labor CD. Similar to other studies, the current research found epidural analgesia to be a protective factor of in-labor CD.²⁴ We propose that the contribution of these factors most likely have the same effect on TOLAC in the preterm population as in the term population and should be further studied. The relatively lower VBAC rate in our institution compared to other centers might be attributed to special characteristics of our study population. In both study centers the parturients are mostly characterized by high order of parity, and therefore TOLAC is advocated. Nonetheless, we employ a conservative approach in these high-risk deliveries, and are vigilant with our decision-making during the labor process, which may tend to result in a higher rate of in-labor cesarean.

Maternal outcomes in our study were generally favorable. The rate of uterine rupture, which is one of serious complication of TOLAC, was comparable between groups. Both Quiñones et al ²⁰ and Durnwald et al¹⁹, compared maternal morbidity in preterm versus term TOLAC. They found lower rate of uterine rupture in preterm TOLAC than term deliveries. These studies postulated that the lower rates of uterine rupture at preterm TOLAC were a result of lower birthweight and thicker lower uterine segment in preterm gestations compared with those at term. Comparable to Durnwald's study¹⁹ our study established that maternal blood transfusion is prevalent in parturients attempting preterm TOLAC than those at term. We propose that the reasons for coagulopathy and blood transfusion in preterm TOLAC are related to higher rates of pathological causes for preterm delivery such as abruption and preeclampsia, rather than exclusively preterm TOLAC. Many preterm deliveries are linked to preterm premature rupture of membrane (PPROM) and chorioamnionitis. ¹⁰ Endometritis is a common result of both chorioamnionitis as well as PPROM. Surprisingly, the rates of endometritis in our study were significantly lower in preterm TOLAC compared to term, similar to those in Durnwald et al study¹⁹.

Likewise, neonatal outcomes in this study were less favorable in preterm TOLAC compared to term. This is not surprising, as preterm neonates are at high risk for mortality and adverse health outcomes. Durnwald et al¹⁹ compared preterm TOL to RCD reported similar neonatal outcomes such as Neonatal Intensive Care Unit (NICU) admission, intraventricular hemorrhage, sepsis, and ventilatory support, after controlling for gestational age at delivery in preterm TOLAC with the exception of a higher rate of respiratory distress syndrome in those delivered after a TOLAC. Other studies that investigated outcomes of preterm birth by mode of delivery did not determine that the mode of delivery affected neonatal outcome. ^{13, 14, 15} Furthermore, previous studies ^{25, 26, 27} determined that the bacterial inhabitants of the neonatal respiratory tract (i.e. Microbiome) differ between those who delivered vaginally compared to those who had CD. The vaginal flora has a favorable effect on neonatal respiratory illnesses in both short and long term.²⁶ In addition, studies^{28, 29} that evaluated the respiratory performance of lambs following vaginal vs cesarean deliveries, demonstrated that lambs who delivered vaginally had better respiratory performance. This was attributed to the reduction of lung liquid volume achieved throughout delivery. This effect was not reached to the same extent in lambs whose lung volume was artificially reduced. It is well established in the literature³⁰ that the neonatal respiratory morbidity when comparing cesarean to vaginal delivery, is not solely related to gestational age at delivery and that vaginal delivery itself has a favorable effect on the neonates' respiratory status. In our study, it was difficult to evaluate the impact of prematurity itself in the preterm group on the neonatal outcomes. A comparison of elective CD versus TOL should be performed in this specific population in order to characterize the specific contribution of TOL to neonatal outcomes in the preterm population.

This study has several strengths. The study addresses an important issue with limited data. Success and safety of preterm TOLAC have not been extensively studied before.

We performed a large-scale population multicenter study comprising more than a half of the births in the Jerusalem vicinity and about 16% of all national births. These two factors contribute to the generalizability of our findings. In addition, our database is validated in real-time, which assists in eliminating potential information bias. Over 95% of Israeli citizens’ medical care is covered by the Israeli National Health Plan, hence continuity of care is granted, and all costs of antenatal care, birth, postpartum care for mother and child are uniformly covered for the entire study period. Moreover, all mother-child data included were solely from the medical centers involved in this study with no transfers to other facilities. These factors alleviate a potential selection bias.

Conversely, our study has several limitations, primarily its retrospective nature. We recognize that our data collection process did not provide information regarding potential risk factors associated with successful VBAC such as the indication for previous CS. Nonetheless, we did attempt to control for most recognized factors and excluded all identified parturients who did not meet the ACOG criteria for TOLAC.³¹

In conclusion, in our study, preterm TOLAC has lower success rates, but similar maternal morbidities compared to TOLAC at term. Prospective studies are required to better evaluate the neonatal results in the preterm TOLAC population. Overall, preterm TOLAC seems to be a safe method of delivery. We suggest that this information be presented in the pre-delivery counseling process to this subset of parturients.

Funding: The authors declare that no funds, grants or other support were received during the preparation of this manuscript.

Competing interests: The authors have no relevant financial or non-financial interests to disclose.

Author contributions: Reut Rotem planned, carried out, analysed and wrote up the article. Ayala Hirsch carried out the study data collection. Moshe Barg helped with planning and conception of study. Pnina Mor helped with conception of study and its editing. Rachel Michaelson-Cohen assisted carrying out, analysing, writing and editing the article. Misgav Rotshenreich participated in writing up of the work. PM edited the article. All authors read and approved the final manuscript.

Ethics approval: The study protocol was reviewed and approved by the local ethics committee- Institutional Review Board (IRB) of the Shaare Zedek Medical Center, in accordance with the principles of the Declaration of Helsinki (IRB: 0411-21-SZMC), date of approval: June 1^st, 2021.

Conflict of interests statement: The authors have no relevant financial or non-financial interests to disclose.

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Trial of labor following cesarean in preterm deliveries: success rates and maternal & neonatal outcomes- a multicenter retrospective study

Status:

Version 1

Abstract

Figures

Introduction

Material And Methods

Results

Discussion

Declarations

References

Status:

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