Induction of labor (IOL) is a prevalent obstetric intervention that initiates labor through artificial means¹. Since 1990, the incidence of labor induction has nearly doubled².International variability in induction of labor (IOL) rates, influenced by differing guidelines and clinical protocols, shows that approximately 25% of neonates are born through IOL in high-income countries, compared to lower rates in low- and middle-income countries, with an estimated 10-30% of obstetric cases requiring induction for various clinical indications³. Indications for induction of labor (IOL) include late preterm, early term, late-term, and post-term deliveries, based on the patient's obstetrical and medical history, and are justified when outcomes for the fetus or mother would be better than with expectant management. The American College of Obstetricians and Gynecologists (ACOG) outlines specific scenarios for IOL, such as oligohydramnios, fetal intrauterine growth restriction (IUGR), chronic hypertension, gestational hypertension, preeclampsia, diabetes, preterm prelabor rupture of membranes (PPROM), abruptio placentae, chorioamnionitis, and intrauterine fetal demise (IUFD)⁴. Induction of labor (IOL) methods are primarily mechanical and pharmacological, with cervical ripening agents used when the Bishop score is unfavorable.

Mechanical options include Foley catheters and osmotic dilators, while pharmacological methods involve synthetic prostaglandins (like misoprostol and dinoprostone) and oxytocin, with caution advised for those with a history of low transverse cesarean sections due to rupture risks. Amniotomy is often combined with these methods, and prostaglandin E2 is available in various formulations to aid in cervical softening and stimulate uterine contractions⁵. Cervical ripening involves softening the cervix to facilitate labor, primarily using Prostaglandin E2 (PGE2 or dinoprostone), which enhances collagenase activity and triggers extracellular matrix remodeling, while nitric oxide and other biochemical changes support this process. However, the clinical efficacy of PGE2 is influenced by vaginal pH—typically acidic—and factors such as parity, coital frequency, and infections, with Lactobacillus bacteria playing a crucial role in maintaining this acidity and potentially modulating PGE2 release⁶. Alterations in vaginal pH may play a significant role in preterm delivery and cervical ripening, potentially influencing the biochemical changes that prepare the cervix for labor, as variations can affect drug absorption and clinical responses. This study aims to assess whether vaginal pH impacts the efficacy of dinoprostone gel for cervical ripening, given its low solubility in acidic conditions, while highlighting that successful induction—evaluated by the Bishop score—depends more on cervical status than on oxytocin, which primarily induces uterine contractions⁷.

AIM

The aim of this study is to compare the efficacy of dinoprostone gel for labor induction in patient with vaginal ph <5.5 and ph ≥ 5.5

This comparative prospective observational study will be conducted in the Department of Obstetrics and Gynecology at Sardar Patel Medical College, Bikaner, over a six-month period from April 2024 to September 2024. The study will focus on pregnant women attending the labor room, utilizing convenience sampling to select a total of 250 participants. The sample size was determined based on an expected prevalence of 20% for women requiring induction, with calculations considering an 80% study power and a 5% alpha error, resulting in a minimum of 125 cases each for those with vaginal pH < 5.5 and ≥ 5.5, accounting for a 10% attrition rate. Inclusion criteria encompass women with an unfavorable cervix (Modified Bishop score < 6), singleton pregnancies in vertex presentation with no contraindications to vaginal delivery, absence of spontaneous uterine contractions, a reactive non-stress test (NST), and ages ranging from 20 to 35 years. Exclusion criteria will include hypersensitivity to prostaglandins, premature rupture of membranes, placenta previa, prior cesarean delivery or uterine surgery, and major cephalopelvic disproportion. This structured approach aims to comprehensively evaluate the efficacy of dinoprostone gel in cervical ripening relative to vaginal pH levels.

MODIFIED BISHOP’S SCORE 

Each component is assigned a score ranging from 0 to 2 or 0 to 3, depending on the criteria. The maximum achievable score is 13. A total score of less than 6 is considered suboptimal and may indicate the necessity for induction

TABLE 1: Distribution of cases according to their Age

The age distribution of participants in Group A and Group B was similar, with 62.4% and 64.8% in the 20-25 year range, respectively, and mean ages of 24.94 ± 4.31 years for Group A and 24.14 ± 3.83 years for Group B, with no significant age difference between the groups (p=0.114).

TABLE 2: Distribution of cases according to their Vaginal pH

All patients in Group A had a pH of less than 5.5, while all patients in Group B had a pH of 5.5 or higher. The mean pH in Group A was 4.24 ±  0.72, compared to 5.90± 0.61 in Group B. (p<0.001) 

TABLE 3: comparison of Bishop Score at 6 hrs in both groups.

20.8% of Group A delivered within 6 hours, compared to 48.8% in Group B, despite Group A having a higher proportion of favorable Bishop scores (≥ 6).

TABLE 4: Distribution of study population according to their Bishop Score at 12 hrs

Between 6 to 12 hours after induction, Group B (82.81%) had a significantly higher delivery rate than Group A (60.61%), despite Group A having a higher proportion of favorable Bishop scores (≥ 6).

TABLE 5: Distribution of cases as per need of induction

In Group A, 58.40% of subjects delivered after single induction, while 41.60% needed a second induction. In contrast, 71.20% of subjects in Group B delivered after single induction, and 28.80% needed a second induction. The difference between the two groups with regard to the number of inductions required was statistically significant (p = 0.047).

TABLE 6: Distribution of cases according to mode of delivery

In Group A, 64.00% of subjects delivered vaginally, while 36.00% underwent a lower segment cesarean section (LSCS). In Group B, 78.40% of subjects had a vaginal delivery, and 21.60% had an LSCS. The difference in the mode of delivery between the two groups was statistically significant (p = 0.018). 

TABLE 7: Distribution of cases according to need of augmentation

In Group A, 39.20% of subjects required augmentation after induction, compared to 37.60% in Group B. 

TABLE 8: Distribution of cases according to NICU addmission

In Group A, 27.20% of subjects required admission to the Neonatal Intensive Care Unit (NICU), whereas in Group B, 11.20% required NICU admission.(p<0.002)

Misoprostol and dinoprostone, commonly used agents for cervical ripening and labor induction, are available in various formulations, including gel, tablets, inserts, and pessaries, and can be administered through different routes such as intravaginal, intracervical, oral, and sublingual.

In this study, the majority of participants in both Group A (62.4%) and Group B (64.8%) were aged 20-25 years, while the smallest proportion were aged 31-35 years, comprising 12.8% of Group A and 11.2% of Group B. The mean age was 24.94 ± 4.31 years in Group A and 24.14 ± 3.83 years in Group B. The age distribution between the two groups was statistically comparable, with no significant difference observed (p = 0.114).

Similarly, Nguyen Duy Anh et al. (2022)⁸ conducted a study that included women with low-risk pregnancies between 39 weeks + 0 days and 40 weeks + 6 days of gestation, all presenting with an unfavorable cervix.

All patients in Group A had a vaginal pH < 5.5, while all patients in Group B had a pH ≥ 5.5. The mean pH in Group A was 4.24 ± 0.72, compared to 5.90 ± 0.61 in Group B, with this difference being statistically significant (p < 0.05). Similarly, Dr. K. Lavanya et al. (2021)⁹ reported that the distribution of vaginal pH among the patients studied ranged from 3 to 6, with a mean vaginal pH of 4.43 ± 0.62 in the study group.

In our study, 20.8% of subjects in Group A delivered within the first 6 hours after induction, compared to 48.8% in Group B. In Group A, the majority (48%) had a Bishop score  ≥ 6, with the lowest incidence (1.6%) having a score of 1, whereas in Group B, 27.2% had a Bishop score ≥ 6, and the lowest incidence (1.6%) had a score of 3. The difference in Bishop scores at admission between the two groups was found to be statistically significant (p > 0.05). Similarly, Dr. K. Lavanya et al. (2021)⁹ reported that after the first application of PGE2 gel, 18% of subjects had a modified Bishop score of ≤5, 52% had a score of 6-10, and 30% had a score of 11-13.

In our study, between 6 to 12 hours after induction, 60.61% of the 99 cases in Group A delivered, while 82.81% of the 64 cases in Group B delivered. Similarly, Dr. K. Lavanya et al. (2021)⁹ reported that the average time to enter the active phase of labor for both groups was 5 hours and 52 minutes.

In our study, among 99 cases in Group A, the highest proportion (26.26%) had a Bishop score  ≥ 6 at 12 hours, with the lowest incidence (1.01%) having a score of 2. In Group B, 17.19% of the 64 cases had a Bishop score less than 6. The difference in Bishop scores between the two groups at 12 hours was found to be statistically significant (p > 0.05). Additionally, 58.40% of subjects in Group A delivered after single induction, while 41.60% required two inductions. In Group B, 71.20% of subjects delivered after single induction, with 28.80% needing a second induction. This difference between the two groups was also statistically significant (p = 0.047). Similarly, Aruna Kumari et al. (2019)¹⁰ observed that the need for a second dose of PGE2 gel was higher in Group II (pH ≥5.5) compared to Group I. Their findings suggest that vaginal pH is an important factor influencing the efficacy of PGE2 gel, with better outcomes associated with higher vaginal pH (pH ≥5.5

In our study, the majority of subjects in Group A (64%) had a vaginal delivery, while 36.0% underwent lower segment cesarean section (LSCS). In Group B, 78.40% had vaginal deliveries, and 21.60% had LSCS. The difference between the two groups was found to be statistically significant (p = 0.018). Jen-Yu Tseng et al. (2020)¹¹ observed that 53 out of 65 patients (81.5%) achieved successful vaginal delivery.

In our study, 39.20% of subjects in Group A and 37.60% of subjects in Group B required augmentation following induction. Similarly, Dr. S. Dhivya et al. (2019)¹² found that out of 54 cases, 23 (85.18%) in Group I required augmentation with oxytocin, whereas 5 (18.51%) in Group II required the same intervention.

In our study, 27.20% of subjects in Group A required NICU admission, compared to 11.20% in Group B. Similarly, Sandhya Kumari et al. (2021) reported that 10.2% of subjects in Group A and 16.3% in Group B required neonatal unit (NNU) admission

The study indicates that assessing vaginal pH before induction with dinoprostone gel can significantly predict labor induction outcomes, with higher pH correlating with better Bishop scores and shorter induction-to-delivery intervals. Of the 250 participants, 178 achieved normal vaginal delivery, emphasizing the potential for improved management strategies. Incorporating vaginal pH assessment into pre-induction protocols may enhance the success rates of labor induction.

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