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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 18  |  Issue : 2  |  Page : 108-113

Predictors of vaginal delivery following stimulation of uterine contractions for term premature rupture of membranes


Department of Obstetrics and Gynaecology, University of Benin Teaching Hospital, Benin City, Edo State, Nigeria

Date of Submission03-Apr-2021
Date of Decision07-Jul-2021
Date of Acceptance25-Aug-2021
Date of Web Publication10-Dec-2021

Correspondence Address:
Dr. Collins Ejakhianghe Maximilian Okoror
Department of Obstetrics and Gynaecology, University of Benin Teaching Hospital, Benin City
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njbcs.njbcs_14_21

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  Abstract 


Context: Premature rupture of membranes (PROM) is a significant event as it may lead to maternal complications, increased operative procedure, neonatal morbidity, and mortality. Aim: To determine the predictors of successful vaginal delivery in pregnant women undergoing stimulation of uterine contractions following premature rupture of membranes (PROM). Settings and Design: This prospective cohort study was conducted at the University of Benin Teaching Hospital, Benin City, Nigeria. Materials and Methods: Seventy-four pregnant women between the gestational ages of 37 weeks and 41 weeks with a live singleton fetus in cephalic presentation and no contraindication to vaginal delivery who had stimulation of uterine contractions following term PROM were included in this study. The main outcome measure was the route of delivery. Statistical Analysis: The analysis was done with IBM statistical package for social science (SPSS) Statistics v21, and a P value ≤0.05 was considered statistically significant. Results: Sixty-two (83.8%) women had a vaginal delivery. The mean age and gestational age were 29.76 ± 3.69 years and 39.04 ± 1.15 weeks, respectively. The chance of vaginal delivery was increased with BMI <30 (RR = 9.091, 95% CI = 1.827–45.246). The duration between rupture of membranes and commencement of stimulation of uterine contractions was ≤8 h (RR = 4.889, 95% CI = 1.307–18.293) also increasing the chance of achieving vaginal delivery. The time interval to 4 cm cervical dilatation ≤4 h (RR = 4.167, 95% CI = 1.141–15.215) and time interval to delivery ≤8 h (RR = 12.222, 95% CI = 2.433–61.402) also favored vaginal delivery. Conclusion: When uterine contractions are stimulated for PROM at term, vaginal delivery is predicted by maternal BMI <30, duration of rupture of membrane ≤ 8 h, and time interval to 4 cm cervical dilatation ≤4 h. Also, it was found was that vaginal delivery becomes less likely when the time interval from stimulation to delivery exceeds 8 h.

Keywords: Labor outcome, predictors, premature rupture of membranes, stimulation of uterine contractions, term


How to cite this article:
Okoror CE, Ezeanochie MC, Ande AB. Predictors of vaginal delivery following stimulation of uterine contractions for term premature rupture of membranes. Niger J Basic Clin Sci 2021;18:108-13

How to cite this URL:
Okoror CE, Ezeanochie MC, Ande AB. Predictors of vaginal delivery following stimulation of uterine contractions for term premature rupture of membranes. Niger J Basic Clin Sci [serial online] 2021 [cited 2022 Dec 9];18:108-13. Available from: https://www.njbcs.net/text.asp?2021/18/2/108/332170




  Introduction Top


In approximately 10% of women with pregnancies at term, the fetal membranes rupture before uterine contractions begin.[1] Premature rupture of membranes (PROM), also known as the pre-labor rupture of membranes, is the spontaneous rupture of the fetal membranes before the onset of labor after the age of viability. When it occurs before 37 completed weeks of gestation, it is known as preterm PROM and after 37 weeks as term PROM. It is a significant event because it may lead to maternal complications, increased operative procedures, and neonatal morbidity and mortality.[2],[3]

The management of term PROM has remained controversial in contemporary obstetric practice. At term, 70% to 95% of pregnancies complicated by PROM will go into labor spontaneously within 24 h in the absence of obstetric intervention.[3],[4] Studies examining the risk of cesarean section with induction of labor have reported varied results, this has made making policies for either early inductions or expectant management difficult.[3],[5],[6],[7] Stimulating uterine contractions early when term PROM occurs may be associated with increased incidence of cesarean delivery, especially when the cervix is unfavorable, whereas delaying delivery to await spontaneous labor may increase the risk of infectious morbidity for the mother and the fetus.

A recent systematic review reported that planned early delivery by stimulation of uterine contractions for term PROM was associated with a lower incidence of maternal infectious morbidity (chorioamnionitis and/or endometritis) and shorter hospital stay. They were also less likely to receive antibiotics compared to those who underwent an expectant management protocol.[3] In addition, the babies born from planned early delivery were less likely to be admitted into the neonatal intensive care unit.[3] Maternal age, weight, height, body mass index (BMI), parity, gestational age, estimated fetal weight, and the state of the cervix have been reported as factors that can influence the mode of delivery.[8],[9],[10],[11],[12],[13]

In our hospital, we practice a protocol of routine planned early delivery by stimulation of uterine contractions after term PROM with no features of spontaneous onset of labor after 2 h of membrane rupture. This might be associated with an increased risk of cesarean delivery.[3] Pregnant women receiving antenatal care in our hospital have a strong aversion to cesarean section.[14],[15] This study was designed to identify and quantify sociodemographic and clinical characteristics that are associated with successful vaginal delivery when stimulation of uterine contractions is initiated for term PROM. Identifying predictors of vaginal birth for women with term PROM will help in patient selection, counseling, and improving client satisfaction with the outcome of labor.


  Materials and Methods Top


This study was a prospective cohort study conducted among a cohort of pregnant women who presented with term PROM at the Department of Obstetrics and Gynecology of the University of Benin Teaching Hospital, Benin City in Nigeria between February and April 2018. Term PROM was defined as spontaneous rupture of fetal membranes at term before the onset of established labor.[4] Ethical approval for this research was obtained from the research ethics committee of the hospital with reference number ADM/E22/A/VOL.VII/145782.

Participants for this study were pregnant women between the gestational ages 37 weeks and 41 weeks plus 6 days with a live singleton fetus in cephalic presentation and no contraindication to vaginal delivery who had stimulation of uterine contractions for term PROM. Women with suspected fetal compromise, hemoglobinopathies, major fetal anomaly, chronic medical conditions, chorioamnionitis, and multifetal pregnancy were excluded.

The sample size was calculated using the Cochran formula[16] with the desired margin of error of 5% at a 95% confidence interval. Assuming the proportion of the characteristics of interest in the population as 2.1% being the prevalence of PROM at term reported in a previous study,[17] a sample size of 32 pregnant women was derived. Considering an attrition rate of 10%, a minimum sample size of 36 was gotten. Seventy-four pregnant women with term PROM, however, participated in this study. Only participants who voluntarily gave informed consent were recruited.

Stimulation of uterine contractions in our center is routinely performed with a low-dose oxytocin infusion protocol when the cervix is adjudged favorable or prior 50 μg intravaginal misoprostol for unfavorable cervix before oxytocin protocol as previously described.[18],[19],[20]

The main outcome of interest in the study was the route of delivery. While the independent variables included the sociodemographic characteristics of the participants, and relevant clinical characteristics including the BMI, duration of membrane rupture, time to develop three contractions in 10 min, time to 4 cm cervical dilatation, total duration of labor, birth weight of baby, Bishop score, and agent were used.

The data were cleaned, coded, and analyzed using IBM SPSS version 21.0 (SPSS Inc. Chicago). A descriptive analysis was carried out on the demographic and obstetric characteristics of the participants. The student t-test and Chi-square test were used for univariate analysis as appropriate, whereas Pearson's correlation coefficient was used to determine the relationship between significant variables. Independent predictors of vaginal delivery were determined using binary logistic regression with an odds ratio (OR) at 95% confidence interval (CI) computed. In all statistical tests, a value of P < 0.05 was considered significant.


  Results Top


The mean age of the participants was 29.76 (±3.69) years and ranged from 23 to 40 years. The gestational age ranged from 37 weeks to 41 weeks plus 6 days with a mean of 39.04 (±1.15) weeks. The mean weight and height of the participants were 78.81 (±10.20) kg and 1.65 (±0.07) m, respectively with an average body mass index (BMI) of 29.24 (±4.12). The majority of the studied participants (54.1%) had an unfavorable Bishop score of ≤5 with a mean cervical dilatation at the admission of 2.14 (±0.97) and median 2 (2–3) [Table 1].
Table 1: Characteristics of the study population

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Sixty-two (83.8%) women had a vaginal delivery, whereas 12 (16.2%) had cesarean section. The majority of the participants (81.1%) experienced 3 or more uterine contractions in 10 min within 3 h of commencing stimulation of contractions (Latent period), had a cervical dilatation of 4 cm or more within 4 h (75.7%), and delivered within 8 h of uterine stimulation (62.2%) [Table 2].
Table 2: Labor outcomes of interest

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The non-obese women (BMI <30) were more likely to have a vaginal delivery and less likely to have cesarean section compared to the obese women. The other clinical characteristics did not have any significant difference when compared across the routes of delivery [Table 3].
Table 3: Relationship between clinical characteristics of participants and route of delivery

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The risk of having a cesarean section increased significantly among women whose duration of stimulation of uterine contractions lasted more than 8 h. Similarly, there was a significantly increased risk of cesarean section when the duration of PROM lasted more than 8 h before the stimulation of uterine contractions. Although not statistically significant across the two routes of delivery (P = 0.059, a sub-group analysis among women who had cesarean section showed that women who achieved a cervical dilatation of 4 cm within 4 h were less likely to have cesarean section (RR = 0.321, 95% CI = 0.118–0.873) [Table 4].
Table 4: Relationship between specific time intervals and route of delivery

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Among the parturients who delivered vaginally, significant positive correlations were seen in the following: the duration of PROM before stimulation of uterine contractions and time to 4 cm cervical dilatation (r = 0.331, P = 0.01), the duration of PROM before stimulation of uterine contractions and the time interval to delivery (r = 0.264, P = 0.05), and between time interval to 4 cm cervical dilatation and time interval to delivery (r = 0.534, P = 0.01). On the other hand, among the participants who had cesarean delivery, there were significant positive correlations between the duration of rupture of membrane and time interval to delivery (r = 0.630, P = 0.05) and time interval to 4 cm cervical dilatation and time interval to delivery (r = 0.927, P = 0.01) [Table 5].
Table 5: Pearson's correlation coefficient of association between variables for the Caesarean section (lower left-hand side) and vaginal delivery (upper right-hand side) groups

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The chance of having vaginal delivery was increased with BMI less than 30 (OR = 9.091, 95% CI = 1.827–45.246), duration between rupture of membrane and stimulation less than or equal to 8 h (OR = 4.889, 95% CI = 1.307–18.293), time interval to 4 cm cervical dilatation of within 4 h (OR = 4.167, 95% CI = 1.141–15.215), and time interval to delivery ≤8 h (OR = 12.222, 95% CI = 2.433–61.402) [Table 6].
Table 6: Predictors of vaginal delivery (Binary Logistic Regression)

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  Discussion Top


Most women (83.8%) in our study delivered vaginally following the stimulation of uterine contractions for PROM at term. In addition, the independent predictors of vaginal delivery were maternal BMI less than 30, duration between rupture of the membrane to stimulation of contractions less than or equal to 8 h, time interval to 4 cm cervical dilatation less than or equal to 4 h, and time interval to delivery less than or equal to 8 h. Our vaginal delivery rate of 83.8%, compares favorably with the 80% vaginal delivery rate in a recent randomized study where labor was induced for term PROM.[21] In our study, women with PROM whose cervix was adjudged to be unfavorable had prior cervical ripening with misoprostol before oxytocin infusion was used to augment labor progress if it was considered necessary. This may have also contributed to the high rates of vaginal delivery observed as misoprostol has been documented to improve vaginal delivery when inducing labor with an unfavorable cervix at term.[22]

Maternal obesity has been associated with adverse pregnancy outcomes including cesarean sections.[23],[24],[25],[26] In our study, obesity more than doubled the risk of a cesarean section. The coexistence of other complications of pregnancy among obese women[23],[24] may further explain why they have higher rates of cesarean section compared to nonobese women. Obesity increases the risk of having gestational diabetes, large for gestational age babies, hypertensive disorders in pregnancy, and induction of labor. We also observed that stimulating uterine contractions within 8 h following the occurrence of PROM was a predictor of vaginal birth. We considered that as the duration of PROM increased before delivery, the risk of maternal exhaustion, fetal distress, and infections morbidity increased during the conduct of labor, this may explain our finding. In a Cochrane review of planned early delivery for term PROM versus expectant management, women in the planned early birth group had more positive experiences of pregnancy compared with women in the expectant management and had shorter time from rupture of membranes to birth and less maternal and neonatal infectious morbidity.[3]

The progress of cervical dilatation to 4 cm within 4 h of commencing uterine stimulation independently predicted vaginal birth. Similarly, delivery within 8 h of commencing uterine stimulation was also a predictor of vaginal delivery. Therefore, it can be inferred that when stimulating uterine contractions in women with term PROM, those who will more likely deliver vaginally will progress to active phase labor timely and will also deliver within 8 h. When progress to active cervical parameters becomes slow or vaginal delivery becomes unlikely after 8 h, we recommend that appropriate measures should be instituted for these women in labor as a safety intervention due to the higher rates of cesarean section.

There were some limitations in our study. We included both nulliparous and multiparous women in our study design, and our study population was a homogenous group of African women in an urban setting. However, from our results, there was no significant difference in the routes of delivery between nulliparous and multiparous women. In addition, the confounding effect of parity in our outcomes was minimized using logistic regression. We recommend multicenter, prospective randomized trials from diverse settings for future studies to improve our understanding of the factors that can predict vaginal birth when uterine contractions are stimulated for PROM at term.

In conclusion, we recognize that PROM at term remains a challenge in obstetrics with no clear consensus on the best approach to management. Based on our study, we recommend that in order to improve the odds of vaginal delivery, women with term PROM should have the stimulation of uterine contractions within 8 h of its occurrence. Maternal obesity, progress to active phase beyond 4 h, and duration of labor exceeding 8 hours are risk factors for cesarean section. This information is useful at the point of care for women with PROM at term. Identifying predictors of vaginal birth for women with term PROM will help in patient selection, counseling, and improving client satisfaction with the outcome of labor. It also contributes to the body of knowledge in the management of PROM at term.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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