Induction of labor is a common obstetric intervention that aims to induce uterine contractions before spontaneous initiation of labor. Labor induction is done in approximately 22.5% of cases with the most frequent indication being prolonged pregnancy. Labor induction has been observed to lower perinatal death in relation to expectant management. The success of labor induction remains a vital challenge in the practice of obstetrics [1,2].

The single most significant predictor of successful vaginal delivery following induction of labour is cervix favorability. Traditionally, this has been assessed using the Bishop's score, a scoring system to assess cervical dilation, effacement, consistency, position, and fetal station. While the Bishop's score is in common usage, it is subjective and has been shown to have a very poor predictive value, particularly in the low-scoring patient. This has led to the evolution of more objective, reproducible measures of cervix readiness before induction [3,4,5].

One such method is transvaginal ultrasound, which has increasingly been applied in obstetrics, particularly in the evaluation of the cervix of high-risk women for preterm labor. Transvaginally measured cervical length provides a more precise evaluation than digital examination, as the entire cervix, including the supravaginal portion, can be assessed, which is approximately 50% of the total length of the cervix. This segment of the cervix is normally difficult to assess by hand, and effacement, beginning at the internal os, cannot be readily estimated in an intact cervix. Sonographic measurement of cervical length is a technique with a number of advantages. It is a reproducible and objective method and can be performed with minimal discomfort to the patient. Transvaginal measurement of the cervical length has been suggested to be an excellent predictor for successful induction of labour. Transvaginal measurement of cervical length could be a valuable addition to standard methods for assessment of cervical preparedness [6,7].

This prospective observational study was conducted at ESIPGIMSR to evaluate the usefulness of pre-induction transvaginal cervical length assessment in predicting mode of delivery. By observing the correlation between cervical length and outcome of labour induction, the study aims to validate the suitability of the use of transvaginal ultrasound as a routine measure in clinical practice. The implication of this research has the potential to improve patient selection for induction, thereby leading to improved maternal and neonatal outcomes. The study also provides an opportunity for the extended use of transvaginal cervical length assessment in obstetric practice, with evidence-based techniques of labour induction.

Study Design and Setting

The study was carried out at ESIPGIMSR, KK Nagar, Chennai, for almost two years, from January 2012 to November 2013. The aim of the study was to assess the value of pre-induction transvaginal cervical length measurement in predicting the mode of delivery after labour induction.

 Study Population

The research involved pregnant women aged 37 to 42 weeks of gestation undergoing induction of labour with intracervical prostaglandin E2 (PGE2) gel. There were 250 participants recruited on a 95% confidence interval and 5% precision calculation. All the participants provided informed consent for both transvaginal ultrasonographic cervical length assessment and induction of labour.

 Inclusion and Exclusion Criteria

Women who were eligible for the study were those with singleton live pregnancies in cephalic presentation and a Bishop's score of less than 4. Other inclusion criteria were a reactive cardiotocography (CTG) trace, post-dated pregnancy, and pregnancy complicated by pre-eclampsia, gestational diabetes mellitus, or Rh-negative status.

Exclusion criteria included women with antepartum hemorrhage, previous uterine surgery, cephalopelvic disproportion, and maternal medical conditions including heart disease, bronchial asthma, hepatic or renal disease, or glaucoma. Women who had a hypersensitivity to prostaglandins or had previously entered spontaneous labour were also excluded from the study.

 Cervical Assessment and Labour Induction Protocol

All the subjects were subjected to a first-time digital cervical examination to assess the Bishop's score. Those with a score of less than 4 were candidates for PGE2 gel induction. Transvaginal ultrasonographic cervical length measurement was done prior to the induction process using a LOGIQ C Series ultrasound machine with a 6 MHz transvaginal probe.

To best visualize the cervix, women were asked to empty their bladder before the exam. The transvaginal probe was inserted into the anterior fornix of the vagina, and the position was adjusted to get a good sagittal view of the entire cervical canal from the internal to the external os. Cervical length was measured three times, and the shortest of the three measurements was used for analysis. Besides cervical length, the cervical canal diameter at the internal os level was also measured. The presence of wedging or funnelling at the internal os was also observed.

After measurement of cervical length, intracervical administration of 0.5 mg of PGE2 gel was done under aseptic conditions with the patient in lithotomy position. Fetal heart rate was recorded pre- and post-gel application. The patient was then put into lateral recumbency for 30 minutes to enable proper absorption of the medication. Induction was repeated at eight-hourly intervals with a maximum of three doses unless the patient went into active labour. Transvaginal cervical length was reassessed before each repeat dose to follow changes in the status of the cervix.

 Labour Monitoring and Definition of Outcomes

Women who developed regular uterine contractions, defined as at least three contractions in ten minutes, were considered to be in active labour. When cervical dilatation reached 4 cm with 80% effacement, artificial rupture of membranes was performed to augment labour progression.

The main finding of the study was to assess if transvaginal measurement of cervical length could be used to predict successful vaginal delivery within 72 hours of induction of labour. Successful induction was taken as the achievement of active labour within 72 hours. Induction failure was diagnosed when active labour was not achieved within 72 hours of the onset of induction.

Also, a failure to advance in active labour was the lack of cervical dilatation for two consecutive hours in the presence of adequate uterine contractions or the failure of fetal descent for one hour. In these situations, a caesarean section was warranted.

The secondary outcomes were the length of the latent phase of labour and the overall length of labour. These parameters were compared with measurements of cervical length to evaluate transvaginal ultrasonography's predictive potential for determining progression of labour.

This potential observational study was conducted to assess the pre-induction transvaginal cervical length measurement for predicting the mode of delivery in 250 pregnant women with a gestational age of 37-42 weeks. The population of the study was induced with PGE2 gel following the measurement of transvaginal cervical length. Demographic and obstetric factors, as well as maternal and neonatal outcomes, were compared to evaluate the predictive ability of cervical length to set the mode of delivery.

Demographic and Obstetric Characteristics

The age range of the study group was 18-35 years, with a mean age of 25.9 years (±3.5 years). Most women (43.6%) were between 26-30 years of age, followed by 42.0% between 21-25 years of age. Primigravida women comprised 65.9% of the study group, and multigravida women comprised 34.1%. The median gestational age at induction was 39.6 weeks and the mean Bishop score was 2.74, with a mean amniotic fluid index of 8.41.

Table 1: Age Distribution

Graph 1: Age Distribution
Graph 1 illustrating the age distribution, with the highest proportion of women in the 26-30 years age group.

Table 2: Obstetric Score and Mode of Delivery

Graph 2: Parity and Mode of Delivery
GRaph 2 shows the association between parity and mode of delivery, highlighting that multigravida women had a higher likelihood of vaginal delivery compared to primigravida women.

Transvaginal Cervical Length and Mode of Delivery

Transvaginal cervical length was a strong predictor of delivery mode. With the Receiver Operating Characteristic (ROC) curve, a cut-off value of 2.65 cm was found with 97.4% sensitivity and 97.8% specificity for the prediction of normal vaginal delivery. Of women with a cervical length <2.65 cm, 97.8% delivered vaginally, and 97.4% of women with a cervical length >2.65 cm had LSCS.

Table 3: Transvaginal Cervical Length and Mode of Delivery

Graph 3: Transvaginal Cervical Length and Mode of Delivery
Graph 3 demonstrating the strong association between cervical length and the likelihood of vaginal delivery or LSCS.

Induction to Delivery Interval and Maternal Outcomes

The average induction-to-delivery time was 20.1 hours (±15.0 hours), with 70.8% delivering in less than 24 hours. Latent phase length was appreciably less for vaginal delivery (mean = 13.1 hours) than LSCS (mean = 25.2 hours). Postpartum hemorrhage was the leading complication (4.4%), whereas 92.4% of the women were complication-free.

Neonatal Outcomes

The mean birth weight was 2.69 kg (±0.37 kg), and 92.8% of the neonates were >2.5 kg. The Apgar score was 8/10 in most neonates (81.6%). Meconium-stained amniotic fluid was the most frequent neonatal complication (10.4%), and NICU admission occurred in 22% of the cases.

Graph 4: Neonatal Complications
Graph 4 illustrating the distribution of neonatal complications, with meconium-stained amniotic fluid being the most frequent.

This article emphasizes the prognostic utility of pre-induction transvaginal measurement of cervical length in the prediction of the mode of delivery. Cervical length <2.65 cm was highly correlated with vaginal delivery, whereas length >2.65 cm predicted LSCS. Parity, BMI, and Bishop score were also predictive factors for the mode of delivery. These observations indicate that transvaginal measurement of cervical length can be a useful parameter in clinical decision-making for labor induction.

The results of this study affirm the prognostic utility of pre-induction transvaginal cervical length assessment in the prediction of mode of delivery. The findings established that a cervical length less than 2.65 cm was highly predictive of successful vaginal delivery, while cervical length above 2.65 cm was predictive of lower segment caesarean section (LSCS). This finding concurs with other studies that have scrutinized sonographic cervical evaluation in labour induction.

The population of the study included women aged 18–35 years, and the largest percentage (43.6%) was in the 26–30 years age group. Most participants (65.9%) were primigravida, and this had a bearing on the overall mode of delivery. Primigravida women were found to have a greater chance of LSCS (56.7%) than multigravida women, who had a higher chance of vaginal delivery (73.3%). These results are in agreement with the literature, where parity has been found to be a significant predictor of the success of labour induction.

One of the main results of this study was the high correlation between cervical length and mode of delivery. The Receiver Operating Characteristic (ROC) curve analysis determined a cut-off cervical length of 2.65 cm, with sensitivity of 97.4% and specificity of 97.8% for the prediction of vaginal delivery. Among women with cervical length below 2.65 cm, 97.8% delivered vaginally, while 97.4% of women with a cervical length above 2.65 cm were delivered via LSCS. These observations are in concordance with the findings of earlier research work by Pandis et al. (2001) [9] and Abdelazim and Abu Faza (2012) [11], both of which proved that transvaginal cervical length measurement prior to induction is an effective predictor of successful vaginal delivery.

The induction-delivery interval was also studied in this research and averaged 20.1 hours. Latent phase duration was markedly less in those women who had vaginal delivery (mean = 13.1 hours) than in those in whom LSCS was needed (mean = 25.2 hours). Results of the present study are consistent with the research conducted by Rane et al.[12], which proved that cervical length measurement can accurately predict induction-delivery interval. Shorter cervical lengths were correlated with a reduced duration of labour and increased chances of successful induction.

Neonatal outcomes were mostly good, with a mean birth weight of 2.69 kg and an Apgar score of 8/10 in the majority of neonates. Meconium-stained amniotic fluid was the most common neonatal complication, seen in 10.4% of cases, and 22% of neonates needed NICU admission. These results are similar to those of Maitra et al. (2009) [13] and Uasseril et al. (2007) [14], who found that pre-induction cervical length did not significantly affect neonatal outcomes but was a significant factor in determining maternal delivery outcomes.

The findings of this study also add to the increasing body of evidence supporting the use of transvaginal ultrasonography in pre-induction cervical evaluation. O'Connell et al. (2003) [8] pointed out the drawbacks of conventional digital cervical evaluation techniques and stressed that ultrasonographic and electrical impedance measurements yield more reproducible and objective information about pre-labour changes in the cervix. Likewise, Yang et al. (2003) [10] concluded that transvaginal measurement of cervical length is a better predictor of successful induction than the Bishop's score based on subjective criteria.

Whereas the Bishop's score is still a common practice in clinical usage, its prognostic capacity is usually inadequate, especially among women with an unfavorable cervix. The study's results correlate with the studies of Rane et al. (2007) [15], who established that sonographic cervical length measurement provides a better and more dependable means of labor induction outcome prediction. In addition, the research conducted by Pandis et al. (2001) [9] also validates the use of transvaginal cervical length measurement as an adjunct in labour management, especially when the Bishop's score is low.

In summary, the findings of this study demonstrate that transvaginal cervical length measurement can be a crucial adjunct in clinical decision-making for labour induction. The results support the contention that a cervical length of <2.65 cm is extremely predictive of successful vaginal delivery, while greater cervical lengths are correlated with a greater chance of LSCS. These findings corroborate previous work and demonstrate the value of the inclusion of ultrasonographic cervical measurement in obstetric care in order to maximize labour induction practices and enhance maternal and neonatal outcomes.

This research emphasizes the important role of pre-induction transvaginal cervical length assessment in determining the mode of delivery. The results show that a cervical length of less than 2.65 cm is strongly predictive of successful vaginal delivery, while a length greater than this is strongly linked with an increased risk of caesarean section. These findings validate the shortcomings of the conventional digital cervical examinations, including the Bishop's score, and justify the incorporation of ultrasonographic cervical measurement as a more objective and consistent instrument in obstetric practice. Parity was also found to affect delivery outcomes, with multigravida women having a greater chance of vaginal delivery. The investigation also demonstrated a definite correlation between cervical length and the interval from induction to delivery, with shorter cervical lengths being related to shorter durations of labour. Neonatal outcomes were generally good, further highlighting the safety and clinical usefulness of transvaginal ultrasonographic measurement. Due to high predictive accuracy, the procedure can be used as a useful adjunct to clinical management, allowing individualized management of labour to maximize maternal and neonatal outcomes. Additional future research and studies of greater scope are indicated to confirm these observations further and evaluate their potential usefulness in other obstetric populations.

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