INTRODUCTION Induction of labor (IOL) is a common procedure in obstetrics which implies stimulation of contractions before the spontaneous onset of labor. The indications for IOL were postterm pregnancy, oligohydramnios , gestational hypertension , chronic hypertension , gestational diabetes mellitus , intrauterine fetal growth restriction and also fetal (1)death . This procedure is important for both safety of mother and baby. There are mechanical and pharmacological techniques for IOL. Mechanical techniques include transcervical catheter, extra amniotic saline infusion, and hygroscopic cervical dilators. Common pharmacological techniques include oxytocin and prostaglandins (PG) such as Misoprostol, a synthet ic PG E1 analogue, can be administered intravaginally, orally and sublingually, it is widely used to (2)terminate pregnancy in the rst and second trimesters . Reported IOL prevalence varies between countries and over (3)time . For example, in Saudi Arabia it was 16% in 2012; in the United States it was approximately 20 % of all births. The United States rate increased from 9.5% in 1990 to 22.8% in (4, 5)2007 and 23.3% in 2012 . The successful rate of IOL and (6-9)associated factors also varied in different reports . This information is necessary for patient's management and counseling. Therefore, the objectives of this study are to determine the prevalence and associated factors of successful IOL, and the maternal and perinatal outcomes in our center. MATERIALS AND METHODS This study is a descriptive study in the Department of Obstetrics and Gynecology, Udonthani Hospital, Udonthani, Thailand. It was conducted after the Human Research Ethical Committee of Udonthani Hospital approved the protocol. Patients' medical records who underwent IOL in Udonthani Hospital from October 2017 to June 2019 were reviewed. The inclusion criteria were; singleton pregnant woman who received IOL during the study period. The indications for IOL were late term pregnancy (gestational age 41 weeks), post term pregnancy (gestational age > 42 weeks), oligohyd ramnios, preeclampsia, chronic hypertension, gestational diabetes mellitus and overt diabetes mellitus, prelabor rupture of membrane, intrauterine fetal growth restriction, chorioamnionitis, fetal anomaly and death fetus in utero. The contraindications of IOL were; previous cesarean delivery or myomectomy, multifetal pregnancy, active genital herpes, estimate fetal weight ≥ 4000 grams. An exclusion criterion was incomplete medical record. The sample size was calculated using a formula for a descriptive study, with an estimated prevalence for a (10)successful IOL 0.65 with 0.06 acceptable error , a 0.05 chance of making a type 1 error. The result was 242 women were needed for the study. The statistical analysis was performed using Stata program version 13. Continuous variables are presented by the mean + standard deviation. Categorical variables are presented by number and percentage. Binary regression analysis was performed to evaluate the difference of variable. Multivariable logistic regression analysis was applied to evaluate the factors associated with successful IOL. Results were presented as adjusted odds ratio with 95% condence interval. A p-value <0.05 was considered statistically signicant. Data collection included patients' baseline characteristics, FACTORS ASSOCIATED WITH SUCCESSFUL INDUCTION OF LABOR IN UDONTHANI HOSPITAL Original Research Paper Chutinan Chantarakhantee* M.D., Department Of Obstetrics And Gynecology, Udonthani Hospital, Udonthani, Thailand. *Corresponding Author X 55GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS Obstetrics And Gynecology BACKGROUND: The prevalence of induction of labor varies between countries. The successful rate of IOL and associated factors also varied in different reports. OBJECTIVE: To determine the prevalence and associated factors for successful induction of labor (IOL). MATERIALS AND METHODS: Medical records of patients who underwent IOL in Udonthani Hospital from October 2017 to June 2019 were reviewed. RESULTS: There were 242 patients who underwent IOL and had completed data. The prevalence of IOL was 3.7% (242/6469) of total deliveries. A Successful IOL was achieved in 126 (52.1%) patients (95% CI 45.6-58.5). Multiparity had a 3.5 times (95% CI 1.76-6.97,p<0.01) higher success rate than nulliparity., Preterm pregnancy increased successful IOL of 3.9 times (95% CI 1.48- 10.49, p<0.01). CONCLUSION: Successful IOL was achieved in about half of the IOL cases. Multiparity and preterm pregnancy were associated with higher IOL success rate. ABSTRACT KEYWORDS : Induction Of Labor, Success Rate, Factors, Bishop Score Srisuda Songthamwat M.D., Department Of Obstetrics And Gynecology, Udonthani Hospital, Udonthani, Thailand. Ueamporn Summart Ph.d. Faculty Of Health Sciences, Udon Thani Rajabhat University, Udonthani, Thailand Metha Songthamwat M.D.,Ph.D., Department Of Obstetrics And Gynecology, Udonthani Hospital, Udonthani, Thailand. VOLUME-8, ISSUE-12, DECEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra 56 X GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS cervical condition and, obstetrics and neonatal outcomes. Successful IOL was dened as vaginal delivery could be achieved. The prevalence and associated factors for successful IOL were analyzed. RESULTS There were 242 patients who underwent IOL and had complete patient data during the study period. The prevalence of IOL in Udonthani Hospital was 3.7% (242/6,469) of total deliveries. Baseline characteristics of the pregnant women and obstetric outcomes are presented in Table 1. The mean age was 26.7± 7.2 years. The mean gestational age was 38.4 ± 3.3 weeks. Mean body mass index at term was 29.1 ± 5.4. The mean Bishop score was 5.2 ± 2.2. The most common indication for IOL was late term in 83 women (34.3%). The most common method of IOL was oxytocin in 129 (53.3%) patients. The mean time for IOL was 20.8+20.0 hours. Successful IOL was achieved in 126 (52.1%) patients (95% CI 45.6-58.5). Comparison of possible associated factors between successful and non-successful IOL groups found advanced maternal age group (age > 35) and preeclamptic patients had a lower IOL success rate. While multiparity, preterm pregnancy had a higher IOL success rate. There were no signicant difference found with body mass index, initial cervical dilatation and effacement, cervical consistency and position, fetal head station and membrane status, induction methods between two groups which shown in Table 2. Maternal and neonatal outcomes are presented in Table3. The neonatal birthweight was higher in the non-successful IOL group. The meconium strained amniotic uid was found to be higher in the cesarean (non-successful IOL) group, however the birth asphyxia was lower in this group than the vaginal delivery (successful IOL) group. There were no difference found in other maternal and neonatal complications in both groups. DISCUSSION This study demonstrated that the IOL prevalence rate in our institute is 3.7%. This rate is less than other reports, such as in (3)USA which approximately 20% of deliveries , 16% in Saudi (11) (12)Arabia , 12.1% in Asia and 4.4% in Africa . Induction of labor rate was higher rate in higher income countries and the elective induction of labor (without indication) is more common. The recent randomized controlled study and meta- analysis reported that elective induction in low risk pregnant women with gestational age more than 39 weeks has the better composite neonatal outcome than expectant (13, 14)management . Successful IOL was achieved in only half of the patients in this study. This rate is lower than previously reported studies which (6-9)the successful IOL rate was approximately 70-80% . This (15)study's rate is closest to Osmundson S, et al study at 56.9 % . The low IOL success rate might be caused by the various and subjective criteria of failed IOL, the unsuitable adjustment of oxytocin dosage, and the discontinuation of IOL in the nighttime, which increase the failure rate of IOL in our center. Associated factors for successful IOL in this study were multiparity and preterm pregnancy. While multiparty is (6-8)similar to previous studies , preterm pregnancy is different from other studies which had higher IOL success rate in term (6-8)pregnancy . Maternal body mass index was similar between groups which is also different from previous studies. Those studies reported higher successful IOL in lower body (6-8)mass index or taller women . Cervical status from Bishop score is not a successful factor in this study which is different (6, 16, 17)from some previous studies , however this result is similar to a systemic review by Kolkman DG, et al which reported that the Bishop score is a poor predictor for the IOL outcome and (18)should not be used for IOL decision making . The most common indication for IOL in this study was late term pregnancy, which is similar to Al-Shaikh GK, et al and (11, 19)Dällenbach P,et al studies . The most common method of IOL was oxytocin which is similar to data in Africa from Vogel (12)JP, et al study . The prevalence, indication and, method of IOL with a high rate of cesarean delivery in our center reects too low of use of IOL. This arose from the fear of its complication especially with misoprostol, although the World Health (20)Organization and the American College of Obstetricians (21)and Gynecologists recommend misoprostol as being safe and effective for IOL. The only two interventions to delivery before the onset of labor are cesarean delivery and IOL, therefore the careful selection of IOL can reduce unnecessary (22)cesarean delivery which cause many complications . This study's limitation is the information was retrospective from a single tertiary care center. A larger prospective multicenter study is needed to indicate the effect on the general population. CONCLUSION Successful IOL was achieved in about half of the IOL cases. Multiparity and preterm pregnancy were associated with higher successful IOL rate. ACKNOWLEDGEMENTS We gratefully acknowledge Dr. Narong Tadadech Director of Udonthani Hospital for permission and grant support. Thanks for Udonthani Hospital staff who participated in this trial. POTENTIAL CONFLICTS OF INTEREST The authors declare no conict of interest. VOLUME-8, ISSUE-12, DECEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra Characteristics Total Vaginal delivery Cesarean delivery P valueβ Total, n (%) 126 (52.1) 116 (48.0) Maternal age (years), n(%) 20-34 <20 >35 Mean ± SD 163 40 39 26.7 ± 7.2 91 (55.8) 19 (47.5) 16 (41.0) 26.1 + 6.9 72 (44.2) 21 (52.5) 23 (59.0) 27.5 + 7.6 0.20 0.14 Parity, n (%) Nullipara Multipara 136 106 60 (44.1) 66 (62.3) 76 (55.8) 40 (37.7) <0.01* Gestational age (weeks),n(%) < 37 ≥37 Mean ± SD 37 205 38.4 ± 3.3 27 (73.0) 99 (48.3) 38.0 + 4.0 10 (27.0) 106 (51.7) 39.0 + 2.1 <0.01* 0.02* IOL:induction of labor, SD: standard deviation, CPD: cephalo pelvic disproportion. Table 1: Comparison of maternal characteristics in succe ssful IOL and non-successful IOL group. X 57GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS VOLUME-8, ISSUE-12, DECEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra Body mass index 2(kg/m ), mean+SD 29.1(±SD 5.4) 28.8 (±SD 5.5) 29.5 (±SD 5.2) 0.26 Bishop score, n(%) <5 ≥5 Mean + SD 85 157 5.2 ± 2.2 38 (44.7) 88 (56.1) 5.3+2.2 47 (55.3) 69 (44.0) 5.1+2.1 0.09 0.35 Cervical dilatation (cm), n(%) <2 ≥2 191 51 95 (49.7) 31 (60.8) 96 (50.3) 20 (39.2) 0.16 Effacement, n(%) ≤50 >50 211 31 108 (51.2) 18 (58.1) 103 (48.8) 13 (42.0) 0.47 Consistency, n(%) Firm Medium Soft 21 70 150 11 (52.4) 32 (45.7) 82 (64.7) 10 (47.6) 38 (54.3) 68 (45.3) 0.48 Station, n(%) -3 -2 -1 0 20 74 126 22 12 (60.0) 36 (48.7) 65 (51.6) 13 (59.1) 8 (40.0) 38 (51.4) 61 (48.4) 9 (40.9) 0.73 Membrane, n(%) Intact Ruptured 202 40 109 (54.0) 17 (42.5) 93 (46.0) 23 (57.5) 0.19 Position, n(%) Posterior Middle Anterior 78 139 25 37 (47.4) 75 (54.0) 14 (56.0) 41 (52.6) 64 (46.0) 11 (44.0) 0.60 Indication for induction, n(%) Late term Pre-eclampsia PROM Other 83 37 43 79 46 (36.5) 11 (8.7) 20 (15.9) 49 (38.9) 37 (31.9) 26 (22.4) 23 (19.8) 30 (25.9) 0.01* Mode of induction, n(%) Misoprostol Oxytocin Misoprostol + Oxytocin Other 55 129 55 3 33 (26.2) 61 (48.4) 31 (24.6) 1 (0.8) 22 (19.0) 68 (58.6) 24 (20.7) 2 (1.7) 0.33 Route of delivery, n(%) Normal delivery Cesarean section Vacuum extraction Breech assisting 117 (48.4) 116 (48.0) 6 (2.5) 3 (1.2) 117 0 6 3 0 116 0 0 Indication of C/S, n(%) Failed induction Fetal distress CPD Chorioamnionitis 63 (54.3) 33 (28.5) 19 (16.4) 1 (0.7) - - - - 63 33 19 1 β -P value was calculated by linear regression analysis for continuous outcome and by binary regression for binary outcome. *statistically signicant difference (P value <0.05) Table 2: Univariate and multiple logistic regression analysis of possible associated factors for successful IOL. Characteristics Vaginal delivery Cesarean delivery OR (95%CI) Adjusted OR (95% CI) P-valve� Maternal age (years) 20-34 <20 ≥35 91 19 16 72 21 23 1 0.72(0.36-1.43) 0.55(0.27-1.12) 1 1.01 (0.44-2.30) 0.40 (0.17-0.94) 0.99 0.02* Parity Nullipara Multipara 60 66 76 40 1 2.09(1.24-3.51) 3.50 (1.76-6.97) <0.01* Gestational age (wks) ≥37 <37 99 27 106 10 1 2.89(1.33-6.27) 3.94 (1.48-10.49) <0.01* VOLUME-8, ISSUE-12, DECEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra REFERENCES 1. Cunningham F, Leveno K , Bloom S, Dashe J, Hoffman B, Casey B, Spong CY. Williams Obstetrics. 25 ed.New York:Mcgraw-hill 2018. 2. Hofmeyr GJ. Induction of labour with misoprostol. Curr Opin Obstet Gynecol 2001;13:577–81. 3. Martin JA, Hamilton BE, Ventura SJ, Osterman MJ, Mathews TJ. Births: nal data for 2011. Natl Vital Stat Rep 2013;62:1-69, 72. 4. Martin JA, Hamilton BE, Sutton PD, Ventura SJ, Mathews TJ, Kirmeyer S, et al. Births: nal data for 2007. Natl Vital Stat Rep 2010;58:1-85. 5. Osterman MJ, Martin JA. Recent declines in induction of labor by gestational age. NCHS Data Brief 2014;1-8. 6. Crane JM. Factors predicting labor induction success: a critical analysis. Clin Obstet Gynecol 2006;49:573-84. 7. Gibson KS, Waters TP. Measures of success: Prediction of successful labor induction. Semin Perinatol 2015;39:475-82. 8. Pevzner L, Rayburn WF, Rumney P, Wing DA. Factors predicting successful labor induction with dinoprostone and misoprostol vaginal inserts. Obstet Gynecol 2009;114:261-7. 9. Tolcher MC, Holbert MR, Weaver AL, McGree ME, Olson JE, El-Nashar SA, et al. Predicting Cesarean Delivery After Induction of Labor Among Nulliparous Women at Term. Obstet Gynecol 2015;126:1059-68. 10. Wayne W. Biostatistics: A Foundation of Analysis in the Health Sciences. 6 ed. John Wiley&Sons, Inc.; 1995. 11. Al-Shaikh GK , Wahabi HA , Fayed AA, Esmaeil SA, Al-Malki GA . Factors 58 X GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS BMI mean (kg/m2), mean+SD 28.77 (SD± 5.46) 29.54 (± SD 5.22) 0.97(0.93-1.02) 0.98 (0.92-1.03) 0.41 Bishop score <6 ≥6 59 67 63 53 1 1.35(0.81-2.24) NA NA Cervical dilatation(cm) <2 ≥2 95 31 96 20 1 1.57(0.85-2.94) 1.59 (0.72-3.50) 0.25 Effacement ≤50 >50 108 18 103 13 1 1.32(0.62-2.83) 1.56(0.58-4.23) 0.38 Consistency Firm Medium Soft 11 32 82 10 38 68 1 0.77(0.29-2.03) 1.09(0.44-2.74) 0.69(0.20-2.44) 1.17(0.34-4.11) 0.80 Station -3 -2 -1 0 12 36 65 13 8 38 61 9 1 0.63(0.23-1.72) 0.96(0.28-3.31) 0.71(0.27-1.86) 0.54(0.16-1.82) 0.68(0.13-3.55) 0.52(0.15-1.77) 0.32 0.65 0.29 Membrane Intact Ruptured 109 17 93 23 1 0.63(0.32-1.25) 0.56(0.22-1.44) 0.23 Position Posterior Middle Anterior 37 75 14 41 64 11 1 1.30(0.75-2.26) 1.41(0.57-3.49) 1.80(0.91-3.56) 1.28(0.42-3.88) 0.09 0.66 Indication for induction Late term Pre-eclampsia Pre labor rupture of membrane Others 46 11 20 49 37 26 23 30 1 0.34(0.15-0.78) 0.70(0.33-1.46) 1.31(0.70-2.46) 1 0.26 (0.09-0.73) 0.79 (0.28-2.24) 1.34 (0.63-2.84) 0.01* 0.66 0.45 Mode of induction Misoprostol Oxytocin Misoprostol+Oxytocin Others 33 61 31 1 22 68 24 2 1 0.60(0.32-1.13) 0.86(0.40-1.83) 0.33(0.02-3.90) 1 0.68 (0.29-1.57) 1.08 (0.46-2.58) 0.34 (0.02-4.95) 0.36 0.86 0.43 IOL: induction of labor, OR: Odd ratio, CI: condence interval. IOL: induction of labor, SD: standard deviation, AF: amniotic uid, NICU: neonatal intensive care unit. β -P value was calculated by linear regression analysis for continuous outcome and by binary regression for binary outcome. *statistically signicant difference (P value <0.05) β -P value was calculated by multiple logistic regression analysis. *statistically signicant difference (P value <0.05) Table 3. Comparison of obstetrics and neonatal outcomes in successful and non-successful IOL groups. Characteristics Vaginal delivery, n(%) Cesarean delivery, n(%) P valueβ Route of delivery 126 (52.1) 116 (48.0) Complication Uterine atony Postpartum hemorrhage 15 (11.9) 9 (7.1) 18 (15.5) 0 (0.0) 0.41 NA Birth weight (gm) 4000+ 2500-4000 <2500 Mean birthweight + SD (gm) 2 (2.0) 94 (74.6) 30 (23.8) 2778.7 + 807.5 4 (3.5) 90 (77.6) 22 (19.0) 2992.3 + 546.5 0.46 0.02* Apgar score<7 at 1 min 23 (18.3) 2 (1.7) < 0.01* Apgar score<7 at 5 min 23 (18.3) 0 (0.0) NA Meconium strained AF 14 (11.1) 20 (17.4) <0.01* NICU admission 1 (0.8) 4 (3.5) 0.14 VOLUME-8, ISSUE-12, DECEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra associated with successful induction of labor. Saudi Med J 2012;33:298-303. 12. Vogel JP, Souza JP, Gulmezoglu AM. Patterns and Outcomes of Induction of Labour in Africa and Asia: a secondary analysis of the WHO Global Survey on Maternal and Neonatal Health. PLoS One 2013;8:e65612. 13. Grobman WA, Rice MM, Reddy UM, Tita ATN, Silver RM, Mallett G, et al. Labor Induction versus Expectant Management in Low-Risk Nulliparous Women. N Engl J Med 2018;379:513-23. 14. Grobman WA, Caughey AB. Elective induction of labor at 39 weeks compared with expectant management: a meta-analysis of cohort studies. Am J Obstet Gynecol 2019;221:304-10. 15. Osmundson S, Ou-Yang RJ, Grobman WA. Elective induction compared with expectant management in nulliparous women with an unfavorable cervix. Obstet Gynecol 2011;117:583-7. 16. Vrouenraets FP, Roumen FJ, Dehing CJ, van den Akker ES, Aarts MJ, Scheve EJ. Bishop score and risk of cesarean delivery after induction of labor in nulliparous women. Obstet Gynecol 2005;105:690-7. 17. Teixeira C, Lunet N, Rodrigues T, Barros H. The Bishop Score as a determinant of labour induction success: a systematic review and meta-analysis. Arch Gynecol Obstet 2012;286:739-53. 18. Kolkman DG, Verhoeven CJ, Brinkhorst SJ, van der Post JA, Pajkrt E, Opmeer BC, et al. The Bishop score as a predictor of labor induction success: a systematic review. Am J Perinatol 2013;30:625-30. 19. Dallenbach P, Boulvain M, Viardot C, Irion O. Oral misoprostol or vaginal dinoprostone for labor induction: a randomized controlled trial. Am J Obstet Gynecol 2003;188:162-7. 20. World Health Organization WHO recommendations for induction of labour. Geneva 2011. 21. Obstetrics ACoPB--. ACOG Practice Bulletin No. 107: Induction of labor. Obstet Gynecol 2009;114:386-97. 22. World Health Organization. WHO recommendations: non-clinical interventions to reduce unnecessary caesarean sections; 2018. X 59GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS