Introduction

Labor induction is used to induce cervical maturation and facilitate cervical maturation. Contraction of the uterus. Approximately 20-30% of all pregnancies need Induction of labour. ^[1] Post-term birth, membrane-free breakage, gestational hypertension, oligohydramnios, unsettling fetal complications and numerous maternal diseases such as chronic hypertension and diabetes are more popular indications. Induction of labour is now one of the world's most effective interventions. Up to 20% of women worldwide had labour in one way or another. The rates of induction differ from experience to cultural context. The presence of better and more predictable modern oxytocic and induction approaches than previous procedures has made the induction mechanism more smooth. ^[2] The most used pharmacological strategies of encouraging cervical ripening and labor inductivity are intravaginal or intracervical administration of PGE2 (dinoprostone) and intravaginal administration of exogenous PGE1 (misoprostol). ^[3] One of the considerations that determine the potency of PGE2 is vaginal pH. ^[4] pH ranges from 4-4.5 the amount of vaginal transudate is affected by the involvement of cervical mucosa. The acid produced by lactobacillus glycogen plays an important role in the preservation of the acidic pH environment in the vagina. ^[5] Many factors may alter normal vaginal pH, including inflammation of the lower genital tract, bacterial vaginosis, membrane rupture, douching, etc. Prostaglandins are organic acids with reduced pH solution solubility. The acidity from the vagina will also affect drug release, resulting in unpredictable clinical outcomes. While a wide range of literature on the effectiveness of prostaglandins for induction has been accessible, relatively few studies have shown variables that impact the overall effectiveness of prostaglandins for induction of labor. The goal of this research is to establish the vaginal pH effect on the efficacy of Dinoprostone (PGE2) gel in cervical maturation in patients with an unfavorable cervix, which will contribute to the patient selection of PGE2 labour triggers and reduce the frequency of induction failure.

Subjects and Methods

Study Design: A prospective observational study

Place of Study: Niloufer Hospital, Osmania Medical College, Hyderabad, India.

Duration: October 2018 to October 2019

Study population : Both pregnant women aged 18-35 who had been admitted into safe confinement in the Department of Obstetrics and Gynecology and were between 37 and 42 weeks of gestation were enrolled. All participants had a diagnostic or obstetric indication for labour induction.

Sample Size: 200 women divided equally into 2 groups.

Inclusion Criteria

• Score of unfavorable cervical bishop ≤ 5,

• No contraindication for delivery by the vagina route;

• NST reactive,

• Lack of involuntary uterine contraction.

• Singleton pregnancy with the presentation of the vertex

Exclusion Criteria

• Documented hypersensitivity to prostaglandins, Placenta previa, Chorioamnionitis presumed,

• Cephalopelvic disproportion, ruptured membranes, clinically apparent genital infection

• Parity of >3;

• Prior effort to induce labor for this pregnancy;

• Prior cesarean delivery or history of uterine surgery;

Results

A total of 200 women with an unfavorable cervix were enrolled in this prospective study. In group I, there were 100 cases with a vaginal pH of ≤4.5 and in group II, 100 cases with vaginal pH of > 4.5. In relation to mother's age, parity, gestation, Bishop's induction score, repeat induction need, induction-active interval process, induction-delivery interval, delivery mode and Neonatal outcomes, vaginal pH was calculated. The mean age in Group I was 25.9 years and Group II was 26.9 years. The range was between 18 and 35 years old. The majority of patients was 37-41 weeks of gestational age and was equally distributed in all categories with a p-value of 0.09. The mean gestational age was 39.5 weeks in group I and 38.9 weeks in group II. There was no statistically meaningful correlation between the two classes with regard to maternal age, gestational age, parity and the original Bishop scores.

The mean Bishop score before labor induction was 3.6±0.9 in Group I and 4±1.0 in Group II. The majority of subjects (60 percent in Group I and 37 percent in Group II) had a pre-induction Bishop score of 4.

No substantial association has been identified between vaginal pH and maternal age. Subjects with a higher vaginal pH (>4.5) required a higher number of inductions compared to subjects with lower vaginal pH, but this observation was not statistically significant. The majority of subjects in both groups required only one dose of PGE2 to initiate labor.

p value=0.28, not significant (p < 0.05 is significant)

Data analysis found that the number of vaginal deliveries was comparable in categories, 90 percent in group I and 87 percent in group II with a p-value of 0.28. The Caesarean section incidence was comparable in both categories (10 percent vs 13 percent) with a p-value of 0.28 as seen in the table above.

There was no substantial variation between groups in the mode of delivery.

In Group II, Bishop's score changes over 6 hours after the start of the first intracervical dinoprostone gel were significantly higher than those in Group I (23 versus 10, p-value 0.15). No substantial relationship has been identified between vaginal pH and induction-active step interval, induction-delivery interval. Out of 200 cases, 14 (23.3 percent) required a rise in Oxytocin, 33 (33.3 percent) in Group I and 13 (13 percent) in Group II.

Analysis of neonatal outcome showed that average birth weight, APGAR score at 5 minutes, need for NICU admission were similar in both the groups. Total 17 babies required NICU care, of which 7 were from the group I and 10 from group II. The most common indication for NICU admission was respiratory morbidity in both groups. All babies were discharged within a week. No perinatal morbidity in both groups.

Discussion

This prospective retrospective research was conducted at the Department of Obstetrics and Gynecology, Niloufer Hospital, Osmania Medical College, Hyderabad, India. A total of 200 term pregnant women have been included in the report. Vaginal pH value was measured prior to induction using both broad and narrow range pH documents. The participants were split into two categories as Group I (vaginal pH ≤ 4.5) & Group II (vaginal pH > 4.5) based on their vaginal pH. The Bishop score was measured after pH assessment. All women with unfavorable cervix were instilled by intracervical administration of the initial dose of dinoprostone gel (0.5mg). After the initial 6 hours of cervical maturation, a repeat score was assigned to the Bishop. The woman with marginal improvement in Bishop Score got up to 3 doses of dinoprostone gel intracervical, 6 hours apart. A standardized intrapartum treatment protocol has been used for all subjects. In this study, the mean maternal age was 25.9±4.4 years in Group I and 26.9±4.5 years in Group II. There has been no important correlation between vaginal pH and maternal age (p-value 0.39). This result was similar to the Goswami et al study (24.4±3.47 years in Group I and 23.13±3.95 years in Group II) and the Onen et al study (22.7±4.3 years in Group I and 23.0±3.7 years in Group II). The mean gestational age in our study was 39.5±0.9 weeks in Group I and 38.9±1.3 weeks in Group II. There has been no substantial correlation between the vaginal pH and the gestational age of the participants. This was like Goswami et al, ^[8] and Onen et al, ^[9] studies. The majority of participants in this sample are primigravida (70 percent in group I and 63.33 percent in group II). No substantial correlation has been identified between the vaginal pH and the parity of subjects (p-value 0.584). The literature has also shown similar results. Kurian et al, ^[10] however, demonstrated a strong correlation between vaginal pH and parity. Subjects with greater parity had a higher vaginal pH (≥5) that was statistically important. In the present analysis, the average Bishop score before induction was 3.6±0.9 in Group I and 4±1.0 in Group II. Our analysis found no substantial connection between the vaginal pH and the pre-induction score of the Bishop. This result was like the analysis of Onen et al. However, Goswami et al and Kurian et al showed a marginally important correlation between vaginal pH and pre-induction of the Bishop score. Subjects with higher vaginal pH had higher Bishop Score scores prior to labor induction. In our research, subjects with higher vaginal pH (>4.5) needed better induction rates relative to subjects with lower vaginal pH, but this finding was not statistically important. The majority of participants in both groups needed only one dose of PGE2 to start work (53.33 percent in group I and 60 percent in group II). However, in the Kurian et al report, subjects with higher vaginal pH (≥5) responded to a single induction, whereas subjects with lower vaginal pH needed a repeat induction (maximum of three doses at 6-hour intervals) that was statistically important. Labor results were identical in both classes in the present study. There was no statistically meaningful correlation between vaginal pH and bishop transition over 6 hours, induction-active step interval, induction-delivery interval, mode of delivery, neonatal outcome.

Bishop Score Change Over 6 Hours

In our study, Bishop's score changes over 6 hours after the start of the first intracervical dinoprostone gel were marginally higher in Group II compared to Group I (23 versus 10) This result was comparable to the Onen et al study, which concluded that the Bishop's score changes over 6 hours after the start of the first vaginal dinoprostone insert were substantially higher in the high vaginal pH group. Goswami et al showed similar results, the improvement in Bishop Score over 6 hours was 2.57 in Group I and 5.71 in Group II.

Induction to Active Phase Interval

In our analysis, the induction-active step interval was significantly higher in Group I compared with Group II (16 hours in group I and 8 hours in group II). The relationship was not statistically important. Our findings were similar to the Onen et al study, in which the period for active labor was 14.7±17.3 in Group I and 13.1±9.8 in Group II. In comparison, Goswami et al demonstrated a strong correlation between vaginal pH and induction-active step period (21.45±8.81 hours in Group I and 11.99±7.65 hours in Group II).

Induction to Delivery Interval

In this study, the delivery interval induction was significantly higher in group I (19 hours) relative to group II (11 hours). The relationship was not statistically important. Our findings were close to those of Onen et al, in which the induction-delivery time was 20.0±21.4 hours in Group I and 17.6±12.0 hours in Group II. In comparison, Goswami et al showed a strong correlation between vaginal pH and induction delivery interval (28.48±7.92 hours in Group I and 16.67±9.350 hours in Group II).

Need for Augmentation of Labor

Out of 200 cases, 46 required augmentations either with Oxytocin, 33 belonged to group I and 13 to group II. Augmentation of labor requirement was slightly higher in group I (33.3% versus 13.3%). This contrasts with the Goswami et al study in which augmentation was required in 7% of subjects in group I and 41% of subjects in group II.

Mode of Delivery

The vaginal delivery rate for our study was 90% in Group I and 87% in Group II. The cesarean section was significantly higher in Group II (13%) than in Group I (10 percent). Goswami et al. reported 20% in Group I and 72% in Group II with vaginal delivery. The Caesarean section level for Group I was 80 percent and Group II was 28 percent. 60.5 percent of those given vaginally in groups I and 76 percent administered in groups II in a study conducted by Onen et al. In Group I, the rate for the Cesarean section was 39.5 percent and in Group II, 24 percent. Basirat et al found that the incidence of cesarean section was lower in women with elevated vaginal pH. In contrast, our study found a higher prevalence of cesarean section in people with higher vaginal pH.

Comparison of Neonatal outcome

Neonatal outcomes like mean birth weight, APGAR score at 5 minutes, need for NICU admission were comparable in both the groups like other studies. Neither our study nor other studies had neonatal deaths.

Conclusion

Our research showed that vaginal pH doesn't seem to have a significant impact on the effectiveness of dinoprostone gel in cervical maturation and labor induction. However, our research's observational evidence indicates that vaginal pH is unlikely to impact the effectiveness of dinoprostone gel.