Pregnancy Outcomes in Women Attempting Vaginal Birth after Cesarean Section Using Oxytocin for Augmentation at Tu Du Hospital

  

    
Factors
    
Vaginal Delivery
      
(N= 85)
    
Cesarean Section
      
(N= 51)
    
OR
    
Adjusted OR
    
P*
  
  

    
Labor Initiation
  
  

    
Labor Induction
    
42 (54,55)
    
35 (45,45)
    
1
    
1
    
 
  
  

    
Spontaneous Labor
    
43 (72,89)
    
16 (27,11)
    
2,11
    
4,36
    
0,006
  
  

    
BISHOP Score at Time of Augmentation
  
  

    
< 5 points
    
11 (45,83)
    
13 (54,17)
    
1
    
1
    
 
  
  

    
5- 6 points
    
54 (61,36)
    
34 (38,64)
    
1,82
    
4,68
    
0,016
  
  

    
= 7 points
    
20 (83,33)
    
4 (16,67)
    
5,91
    
14,30
    
0,003
  
  

    
Birthweight (gram)
  
  

    
< 2500
    
23 (82,14)
    
5 (17,86)
    
1
    
1
    
 
  
  

    
2500 – 2950
    
24 (64,86)
    
13 (35,14)
    
0,37
    
0,27
    
0,158
  
  

    
3000 – 3450
    
29 (55,77)
    
23 (44,23)
    
0,27
    
0,11
    
0,030
  
  

    
= 3500
    
9 (47,37)
    
10 (52,63)
    
0,20
    
0,06
    
0,014
  

Table 5: Factors associated with vaginal delivery in women with prior cesarean
scar underwent augmentation.

Discussion

We reviewed all cases of women with prior Cesarean section undergoing trial of labor who had oxytocin augmentation as per Tu Du hospital’s current protocol. Of the 136 cases that fulfilled our criteria, 85 women successfully delivered vaginally (62.5%), and 51 women had repeated Cesarean section (37.5%). In the vaginal birth group, the rate of normal vaginal delivery was 5.07 times higher than assisted instrumental delivery.

The vaginal birth rate after Cesarean section in our study is higher than in Tuan’s study (54.14%), which was also conducted at Tu Du hospital in 2014 [7]. This difference could be attributed to the implementation of the “Labor augmentation with oxytocin in women undergoing trial of labor after Cesarean section” protocol at our hospital at the time of our study, which regulates the frequency and intensity of contractions to be optimally consistent with labor stage. Our vaginal birth rate was also higher than that seen in Gobillot’s study, who reported the rate of vaginal birth after Cesarean section as 58.5%. In addition, 81.71% delivered vaginally in the BISHOP ≥ 6 group, which indicated that the use of oxytocin in women undergoing trial of labor after Cesarean section who have a favorable cervix will be more likely to be able to facilitate vaginal birth [9].

A study by Kohei Nakamura, conducted in Japan, reported 72.7% of women who had a prior Cesarean section delivered vaginally, while 12.6% of them had a repeated Cesarean section before labor and 14.7% had an emergency Cesarean section during labor [10]. Compared to ours, the higher vaginal birth rate seen in Kohei Nakamura’s study could be explained by the elimination of cases with labor induction, and oxytocin use, both before and during labor.

The mean blood loss during the first 24 hours after birth was 223.72 ± 149.40 mL, ranging from 50 mL to 1350 mL. There were 6 cases of postpartum hemorrhage (blood loss ≥ 500 mL), all delivered vaginally (7.06%). Furthermore, there was 1 case with a third-degree perineal tear, cervical laceration, and 1350 mL blood loss after instrumental delivery, and transfusion was indicated. Our postpartum hemorrhage rate is higher than Tuan’s report of 6.02% [7], which demonstrates the use of oxytocin for augmentation is a risk factor for postpartum hemorrhage, mostly due to uterine atonia from overstimulation. Therefore, oxytocin use should be restricted to cases with a clear indication for it.

There were no cases with bladder, ureter, or intestine injury. There were no instances of uterine rupture in our 136 observed cases. The uterine rupture incidence in our study is lower than levels in the Tuan and Vidyadhar reports, which were 1%, and 2%, respectively [7,11]. The uterine rupture incidence from Gobillot’s report was 3%, which is also higher than ours [9]. The higher dose of oxytocin used in Gobillot’s study, which was 2.5 mIU/min for both starting and incremental dosing compared to 1 mIU/min for starting and incremental dose in our protocol, could have contributed to the difference in the uterine rupture incidence.

There were 25 cases of stillbirth in our study (18.38%) and most of these cases had some major fetal malformations, for which feticide was performed prior to termination of pregnancy. The rest of the study population accounted for 111 cases of livebirth in our study (81.62%). Most of the neonates had an Apgar score at 1 minute of ≥ 7 (105 cases, 93.75%), and 6 cases had a 1-minute Apgar score of < 7 (6.25%). After resuscitation, all of the neonates had a 5-minute Apgar score of ≥ 7.

The rate of vaginal delivery in the spontaneous labor group was 4.36 times higher than in women whose labor was induced (P < 0.05, CI 95% [1,52 – 12,44]). This is consistent with Tuan’s reported results from 2014 [7].

It was also found that women with a higher the BISHOP score at the time of augmentation had a higher chance of completing a successful vaginal birth when undergoing trial of labor after Cesarean section. Specifically, this association was clearly seen in the 5 – 6-point group (OR = 4.68, CI 95% [1,34 – 16,37]) and the ≥ 7-point group (OR = 14.30, CI 95% [2,52 – 81,25]). We draw the same conclusion as Tuan, Vidyadha, and Gobillot, who all state that a high BISHOP score is associated with a higher likelihood of a successful vaginal birth after Cesarean section [7,9,11].

Birthweight is also a predictor of successful vaginal birth after Cesarean. Compared to the group of women with birthweight below 2500g, women whose neonatal birthweight was more than 3500g had their likelihood of successful vaginal delivery reduced by 94% (P < 0.05, CI 95% [0,007 – 0,57]). In addition, women with a neonatal birthweight of 3000g to 3450g were 89% less likely to deliver vaginally (P < 0.05, CI 95% [0,02 – 0,81]). Gobillot’s study also concluded that birthweight of more than 3000g significantly reduces the rate of vaginal delivery in women with prior Cesarean section.

Conclusion

We report a rate of successful vaginal delivery in women with prior Cesarean section undergoing labor augmentation with oxytocin of 62.5%, which is higher than previously reported at Tu Du hospital. We also observed a 0% incidence of maternal and neonatal mortality.

Therefore, our study has shown that the correct use of oxytocin during labor in order to regulate the frequency and intensity of contractions to be consistent with labor stage is safe, with an especially high chance of successful vaginal birth after Cesarean section in women with a BISHOP score ≥ 7. However, these women need to be monitored closely and appropriately managed should adverse events occur.

We are planning to conduct a larger study that is powered enough to identify factors associated with successful vaginal birth after Cesarean section with oxytocin use.

Acknowledgement

We are indebted to the participants for making this research possible and to all physicians and staffs of Delivery Unit of Tu Du hospital.

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