Arch Gynecol Obstet DOI 10.1007/s00404-015-3765-3
MATERNAL-FETAL MEDICINE
Mechanical labor induction in the obese population: a secondary analysis of a prospective randomized trial Saja Anabusi1 • Elad Mei-Dan1 • Mordechai Hallak1 • Asnat Walfisch1
Received: 22 February 2015 / Accepted: 26 May 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Objective The objective of this study was to estimate the influence of maternal body mass index (BMI) on progress and outcomes of labor induction using mechanical devices. Methods This study was a secondary analysis of data collected during the Cook Catheter vs. Foley Catheter study, a series of prospective randomized trials of women requiring cervical ripening for labor induction. The duration, characteristics, and outcomes of labor were analyzed after stratification by BMI categories. Outcomes assessed included time from device insertion to delivery, successful ripening, cesarean delivery rates, and any maternal and neonatal adverse events. Results One hundred and eighty-one patients were stratified according to BMI categories, with 102 study participants classified as normal weight (BMI B30) and 79 as obese (BMI [30). Maternal satisfaction from the induction process was significantly lower in the obese group compared to the normal weight group (5.95 ± 3.14 vs. 7.58 ± 2.7, respectively, in a 1–10 scale, p = 0.009). The cesarean delivery rate was similar in the normal weight and the obese groups (17.6 vs. 25.3 %, respectively, p = 0.27). No statistical differences were found in all other outcomes evaluated, including a sub-analysis of the different mechanical devices.
Presented in part at the 32nd Annual Meeting of the Society for Maternal–Fetal Medicine, Dallas, Texas, February 6–11, 2012. & Saja Anabusi [email protected] 1
Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, affiliated with the Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, P.O.B. 169, 38100 Hadera, Israel
Conclusions During the process of mechanical cervical ripening, maternal satisfaction, but not objective obstetrical parameters, was influenced by increased maternal BMI. The trial is registered at ClinicalTrials.gov, no: NCT00604487. Trial registry name is ‘‘Induction of Labor in Patients with Unfavorable Cervical Conditions.’’ Keywords Induction of labor Balloon Obesity Overweight
Introduction Obesity (Body Mass Index—BMI of [30 kg/m2) has become a worldwide epidemic in the last few decades with a prevalence that varies widely depending on the definition, location, genetics, and other demographic characteristics. In the United States, more than one-third of women are obese, and 8 % of reproductive aged women are extremely obese (BMI [40 kg/m2) [1]. Numerous studies suggest an association between obesity and pregnancy complications. Obesity is associated with anovulation and subfertility [2] as well as with poorer outcome of infertility treatment [3]. Additionally, obese women suffer from increased rates of miscarriages [4] and a variety of pregnancy complications [5–9]. Intra-partum complications and labor induction are also more common [5, 6, 10–16] as are postpartum complications [17–19], and BMI was found to be an independent predictor of cesarean delivery among nulliparous morbidly obese women [20]. Lastly, fetal and neonatal risks including low Apgar score, prematurity, stillbirth, congenital anomalies (neural tube defects—NTD), and childhood and adolescence obesity were reported to be associated with maternal obesity [6, 12, 21].
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Arch Gynecol Obstet
Labor induction is one of the most commonly performed obstetrical interventions. Although multiple methods for cervical ripening and labor induction exist, the search for the optimal method is ongoing. Mechanical methods for cervical ripening, specifically cervical balloon catheters, have the advantage of ripening the cervix without inducing simultaneous uterine contractions [22–24]. Moreover, mechanical methods have been repeatedly shown to be as effective as pharmacological methods in cervical ripening [24, 25] with comparable or even higher vaginal delivery rates [26]. This study is a secondary analysis of two previously published randomized controlled trials, conducted by our group, comparing mechanical devices for cervical ripening. In this sub-analysis, we focused on the possible effect of maternal BMI on the progress and outcomes of cervical ripening and labor induction performed using different mechanical devices [27, 28].
Methods This study is a secondary analysis of data collected during the Cook Catheter vs. Foley Catheter Study [27, 28], a series of prospective randomized trials involving women requiring cervical ripening using different mechanical techniques for cervical ripening. The study was conducted between November 2007 and Jan 2011 at the Hillel Yaffe Medical Center, Hadera, Israel. The study was approved by the local institutional review board. The studies’ protocols are detailed elsewhere [27, 28] and are summarized here. We included patients with a singleton pregnancy in a vertex presentation with intact membranes at term (37 completed weeks or more). Eligible women were planned for induction of labor for various indications, and all had an unfavorable cervix (Bishop score B4). We excluded women with contraindications for a vaginal delivery (i.e., placenta previa, non-vertex presentation), presence of ruptured membranes, presence of a uterine scar, and suspected fetal distress necessitating immediate intervention. Eligible women were given an explanation as well as an information sheet followed by an informed consent form. Prior to randomization, we collected data on the patients’ medical and gynecological history, physical and vaginal examination, initial Bishop score, ultrasonography for fetal position and weight estimation, and the biophysical profile score. A suitable patient was one who met all the inclusion criteria specified above and signed the informed consent form. Following randomization, either a Foley catheter or the Cook cervical ripening balloon catheter (with or without EASI) was inserted into the cervical canal. Specific considerations of the insertion technique are detailed elsewhere [27, 28].
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Following the insertion of either device, a 30-min nonstress test monitoring was completed. All participants rated the pain associated with the catheter insertion procedure using a visual analog scale (0–10, 0 = no pain, 10 = worst possible pain). Balloon expulsion was regularly monitored by the medical team and in any case of a change in reported symptoms. Twelve hours after insertion of the device, if not spontaneously expelled, the balloons were deflated, and the device was removed. Immediately following balloon expulsion or removal, the Bishop score was reassessed. Induction of labor was commenced in any of the following cases which were considered to be successfully ripened: second Bishop score increases by two points or more or a cervical dilation of 3 cm or more. Methods of labor induction included intravenous administration of oxytocin and/or artificial rupture of the membranes. Standardized oxytocin and labor induction protocols were followed in all cases. In all other cases, failure of the method used to ripen the cervix was declared, and the patient was re-evaluated for a different cervical ripening/labor induction method according to the obstetrical circumstances (most commonly using vaginal prostaglandins E1 or E2). Active labor was defined as cervical dilatation of 4 cm or more in the presence of regular uterine contractions. The primary outcome of the original trials was time from device insertion to delivery. Secondary outcomes included successful ripening rate, cesarean delivery rate, any occurrence of maternal or fetal adverse events, and maternal satisfaction from the induction process. Here, we assessed the cervical ripening and labor induction duration, mode of delivery, and feto-maternal outcomes, as well as maternal labor experience satisfaction. All these outcomes were stratified by different BMI categories. Statistical analysis For the original study, sample size was determined by Win Epi-scope 2 for independent samples. We anticipated a 20 % difference (0.5 SD) in the induction-to-delivery interval between the different devices. For a period of 4 years, we assigned all eligible women who presented for induction, on even months to the Cook cervical ripening balloon group and on odd months to the Foley catheter group. Analysis was performed according to the intention to treat principle. Data analysis was performed with the SPSS package version 15 (SPSS, Chicago, Illinois, USA). We divided the entire study population into 2 subgroups according to the body mass index (BMI): normal weight was defined as BMI B30, and obesity was defined as BMI [30. Descriptive statistics for continuous variables included mean, standard deviation, median, and percentiles. Differences in the continuous variables were
Arch Gynecol Obstet
performed by Student’s t test and the Mann–Whitney U test. Differences in the categorical variables were analyzed using the Chi-square test and the Fisher exact test. A p B 0.05 was considered statistically significant.
Results One hundred eighty-one patients were stratified according to BMI categories, with 102 classified as normal weight (BMI B30) and 79 classifiedas obese [BMI [30, Study flow chart (Fig. 1)]. There was no difference in mean BMI values between the different mechanical device groups, including: double-balloon catheter, Foley catheter with EASI, or double-balloon catheter with EASI (30.26 ± 5.2, 29.83 ± 5.5, 29.47 ± 4.7, p = 0.38) respectively. In addition, rates of obese women (BMI [30) in the double-balloon catheter, double-balloon catheter with EASI, and Foley catheter with EASI groups were comparable (44.8, 33.3, 44.3 %, respectively, p = 0.7). Patients’ demographic characteristics did neither differ in the two groups (Table 1) nor did the indications for labor induction (Table 1). Additionally, there were no differences in fetal assessment before labor induction except for estimated fetal weight prior to delivery. The Bishop score prior to balloon insertion or following its expulsion did not differ between the groups (Table 2), and there was no difference in the reported technical difficulty or in the patients’ reported discomfort (Table 2). Assesed for eligibality n=286 Data on BMI (n=181) 63.3%
Missing BMI data (n=105) 36.7%
BMI≤30 (n=102)
BMI>30 (n=79)
56.4%
43.6%
48a (47%)
39 a(49.4%)
Double ballon catheter
Double ballon catheter
44 a,b(43.2%)
35 a,b(44.3%)
Foley catheter with EASI
Foley catheter with EASI
10 b (9.8%)
5a (6.3%)
Double ballon catheter with EASI
Double ballon catheter with EASI
Fig. 1 Study flow chart: aMei-Dan et al. [27], bMei-Dan et al. [28]
Following either balloon insertion, there were no differences between the groups in ripening success, balloon insertion to delivery interval, time to expulsion, or mode of delivery (Table 2). Although no differences were noted in almost all primary and secondary obstetrical outcomes assessed, obese women were significantly less satisfied from the labor induction process, compared to the normal weight group (5.95 ± 3.1 vs. 7.58 ± 2.7, respectively, in a 1–10 scale, p = 0.009). Regarding fetal outcomes, there were no significant differences in neonatal mean birth weights or Apgar scores (Table 2).
Discussion Our results show that the process of mechanical cervical ripening was not affected by maternal obesity. Following stratification of the study participants into two BMI categories, no differences were noted in ripening success, induction length, or mode of delivery. In previous studies, BMI was found to be an independent predictor of cesarean delivery among nulliparous morbidly obese women [20]. For example, Saylawala et al. [29] retrospectively studied a cohort of 502 nulliparous women undergoing induction of labor at term, using balloon cervical ripening. He found cesarean delivery rate to be significantly higher in the obese subgroup compared with non-obese women (54.9 % compared with 37.9 %, p = 0.001). Another example is the secondary analysis, published by Pevzner et al. [30], of the data collected during the Misoprostol Vaginal Insert trail. Here too, patients were stratified according to BMI categories, and the incidence of cesarean delivery was examined. The rate of cesarean delivery increased with the BMI. In our study, there were no differences in the mode of delivery between the groups. Possibly, this is a result of a smaller study size and a lower degree of obesity in our study population. Another point is the method of cervical ripening used in our study. All women in both groups underwent pre-induction cervical ripening by a mechanical device (either double-balloon catheter or Foley, with or without EASI) as opposed to a pharmacological method. We suspect that our results can testify to a potential superiority of mechanical cervical ripeners compared to pharmacological methods specifically in the obese population. Theoretically, mechanical cervical ripening in obese women may be superior to pharmacological agents due to the different nature of these two interventions with the mechanical method being more independent of maternal weight. A significant difference between the two groups was the estimated fetal weight prior to delivery. Obese women were estimated to have heavier fetuses than lean
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Arch Gynecol Obstet Table 1 Demographic Characteristics and Baseline Fetal Assessment
Characteristics
BMI B30 (n = 102)
BMI [30 (n = 79)
p value
Maternal age (year)
28.03 ± 5.5
28.76 ± 5.5
0.38
Family status (% married)
97 (95.1 %)
78 (98.7 %)
0.28
Gestational age upon enrollment (week)
39.48 ± 2.0
39.57 ± 1.7
0.76
43 (42.6 %)
26 (32.9 %)
0.22
Ethnic origin (%) Native Israeli Arabic
41 (40.6 %)
40 (50.6 %)
0.22
Nulliparity (%)
54.5
47.4
0.36
Grand-multiparitya (%)
5
7.7
0.53
Elementary school
5 (5.6 %)
9 (13.2 %)
0.15
High school
46 (51.1 %)
37 (54.4 %)
0.74
University
39 (43.3 %)
22 (32.4 %)
0.24
86 (85 %)
59 (76 %)
0.12
14 (13.7 %)
18 (24 %)
Post-datec
13 (22 %)
19 (24 %)
Pre-eclampsia
10 (10 %)
9 (11 %)
0.81
NRFHRd monitoring
23 (22 %)
12 (15 %)
0.26
Diabetes
10 (10 %)
11 (14 %)
0.48
Oligohydramnione
30 (29 %)
31 (39 %)
0.20
Other
32 (31 %)
32 (31 %)
0.24
Fetal estimated weight (gr)
3200 (1374–4130)
3293 (1606–4300)
0.026
Amniotic Fluid Index (AFI) (cm, median, range)
7.5 (0–31)
4 (0–43)
0.5
Normal Non-Stress Test (%)
83 (81.4)
67 (84.8)
0.69
Contractions upon admission
28 (27.5)
14 (17.7)
0.15
Education (%)
General medical history (%) No known illness Otherb Indication for labor induction
0.86
Primary fetal assessment
Data are in numbers (valid %) or mean ± SD a
Grand-multiparity [4 deliveries
b
Other—including diabetesmellitus, hypertension, asthma, chronic infectious diseases, ischemic heart disease, thyroid dysfunction, and other
c
Defined as [40 completed weeks of gestation
d
NRFHR—Non-reassuring fetal heart rate
e
Defined as less than 5 cm amniotic fluid index
women, (3200 vs. 3293, respectively, p = 0.026) although the actual birth weight was virtually the same (3145 vs. 3195 gr p = 0.29). This difference maybe a result of the technical challenge involved in clinical and sonographic assessment of fetal weight in the obese population [31]. Our results showed differences in the satisfaction rates between the groups, with the obese women reporting less satisfaction from the process, compared with the normal BMI group. Of note is the fact that the obese women did neither report more pain during the insertion process (3.57 ± 2.4 vs. 3.26 ± 2.2, p = 0.54) nor did the physician report more difficulty in the insertion (80.7 vs. 76.8 %,
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p = 0.55), and thus this cannot explain the lower satisfaction rate. In an attempt to explain the lower satisfaction rate in the obese group, unrelated to any objective outcomes assessed, we assume that this relates to maternal emotional state. It is well established that depression is more common in the obese population in general and in pregnancy and the post-partum period as well [31]. LaCoursiere et al. [32] have screened 1053 women for post-partum depression, stratified by BMI. Roughly, 15 % of normal weight women screened positive for postpartum depression, and depression rates increased progressively as BMI increased (p \ 0.01). We suspect that this may have to do with the lower satisfaction rates in the obese
Arch Gynecol Obstet Table 2 Balloon Insertion and Labor Outcome Outcomes
BMI B30 n = 102 (valid %)
BMI [30 n = 79 (valid %)
p value
Bishop score before balloon insertion (median, range)
2.49 (0–4)
2.42 (0–4)
0.71
Bishop score after balloon expulsion (median, range)
6.5 (2–9)
6.45 (3–9)
0.82
Spontaneous balloon expulsion (valid %)
35 (34.7)
25 (32.1)
0.75
Difficulty during balloon insertion
a
72 (80.9)
53 (76.8)
0.55
Pain perception during catheter insertion (VAS range 1–10, mean ± SD)
No difficulty (valid %)
3.57 ± 2.4
3.26 ± 2.2
0.54
Ripening successb
98.0
94.9
0.41
Spontaneous rupture of membranes
37 (44)
39 (60.9)
0.04
Balloon insertion todelivery time (median, hours:minutes)
16:00
16:57
0.092
Insertion to expulsion (median, hours:minutes)
11:15
11:30
0.19
Delivery mode VD, n (%) CS, n (%) Birthweight (gr) (mean ± SD) Use of analgesia
c
84 (82.4)
59 (74.6)
0.16
18 (17.6)
20 (25.3)
0.27
3145 ± 596
3195 ± 488.6
0.29
86 (86.9)
69 (90.8)
0.48
Total hospitalization (mean in days ± SD)
6.11 ± 5.5
5 ± 3.885
0.76
Maternal satisfaction (VAS range 1–10, mean ± SD)
7.58 ± 2.7
5.95 ± 3.1
\0.01
1 min
9 (0–10)
9(4–10)
0.16
5 min
10 (7–10)
10 (6–10)
0.58
Apgar score (0–10)
a
Rated by the caregiver: 1—no difficulty at all, 5—extremely difficult
b
Successful ripening defined as second Bishop score increases by two or more points or cervical dilatation of 3 cm or more
c
Of any type including Epidural or Pethidine or both
subgroup of our study although depression was not assessed in our study population. Our study’s main strength lies in its prospective randomized design, and the fact that both obese and normal weight women demonstrated comparable demographic characteristics. Although the study was originally randomized to three different mechanical ripening methods (the Cook ripening double-balloon catheter with or without EASI and the Foley catheter with EASI), the distribution of BMIs between the original study groups was similar, and thus we could disregard the type of balloon used in our analysis. The main weakness of our study lies in the fact that it is a sub-analysis of a previous study designed for a different purpose and different outcome measures. However, as the rates of obesity were similar in all 3 study arms, and the distribution of intervention in the obese and non-obese subgroups was virtually the same, we feel this point did not bias our results. In summary, our study demonstrates that except for a lower mean maternal satisfaction rate, mechanical cervical ripening as a part of labor induction is not influenced by increased maternal BMI. As obesity is a major challenge in modern obstetrics, further studies are needed to corroborate
our results and better define the optimal cervical ripening and labor induction methods to be used in the maternal obese sub-population. Conflict of interest
The authors report no conflict of interests.
References 1. American College of Obstetricians and Gynecologists (2013) Obstet Gynecol 121(1):213–217 2. Maheshwari A, Stofberg L, Bhattacharya S (2007) Effect of overweight and obesity on assisted reproductive technology—a systematic review. Hum Reprod Update 13:433 3. Wang JX, Davies M, Norman RJ (2000) Body mass and probability of pregnancy during assisted reproduction treatment: retrospective study. BMJ 321:1320 4. Metwally M, Ong KJ, Ledger WL, Li TC (2008) Does high body mass index increase the risk of miscarriage after spontaneous and assisted conception? A meta-analysis of the evidence. Fertil Steril 90:714 5. McDonald SD, Han Z, Mulla S et al (2010) Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses. BMJ 341:c3428 6. UshaKiran TS, Hemmadi S, Bethel J, Evans J (2005) Outcome of pregnancy in a woman with an increased body mass index. BJOG 112:768
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Arch Gynecol Obstet 7. Cnattingius S, Villamor E, Johansson S et al (2013) Maternal obesity and risk of preterm delivery. JAMA 309:2362 8. Liu Xuemin, Juan Du, Wang Guixi et al (2011) Effect of prepregnancy body mass index on adverse pregnancy outcome in north of China. Arch Gynecol Obstet 283:65–70 9. Pallasmaa Nanneli, Ekblad Ulla, Gissler Mika, Alanen Anna (2015) The impact of maternal obesity, age, pre-eclampsia and insulin dependent diabetes on severe maternal morbidity by mode of delivery—a register-based cohort study. Arch Gynecol Obstet 291:311–318 10. Vahratian A, Zhang J, Troendle JF et al (2004) Maternal prepregnancy overweight and obesity and the pattern of labor progression in term nulliparous women. Obstet Gynecol 104:943 11. Buhimschi CS, Buhimschi IA, Malinow AM, Weiner CP (2004) Intrauterine pressure during the second stage of labor in obese women. Obstet Gynecol 103:225 12. Perlow JH, Morgan MA (1994) Massive maternal obesity and perioperative cesarean morbidity. Am J Obstet Gynecol 170:560 13. Wolfe KB, Rossi RA, Warshak CR (2011) The effect of maternal obesity on the rate of failed induction of labor. Am J Obstet Gynecol 205:128 14. Poobalan AS et al (2009) Obesity as an independent risk factor for elective and emergency caesarean delivery in nulliparous women–systematic review and meta-analysis of cohort studies. Obes Res 10:28 15. Gunatilake RP, Smrtka MP, Harris B et al (2013) Predictors of failed trial of labor among women with an extremely obese body mass index. Am J Obstet Gynecol 209:562.e1 16. Robinson HE, O’Connell CM, Joseph KS, McLeod NL (2005) Maternal outcomes in pregnancies complicated by obesity. Obstet Gynecol 106:1357 17. Heit JA, Kobbervig CE, James AH et al (2005) Trends in the incidence of venous thromboembolism during pregnancy or postpartum: a 30-year population-based study. Ann Intern Med 143:697 18. Jacobsen AF, Skjeldestad FE, Sandset PM (2008) Ante- and postnatal risk factors of venous thrombosis: a hospital-based case-control study. J Thromb Haemost 6:905 19. Larsen TB, Sørensen HT, Gislum M, Johnsen SP (2007) Maternal smoking, obesity, and risk of venous thromboembolism during pregnancy and the puerperium: a population-based nested casecontrol study. Thromb Res 120:505 20. Gunatilake RP, Smrtka MP, Harris B, Kraus DM, Small MJ, Grotegut CA, Brown HL (2013) Predictors of failed trial of labor among women with an extremely obese body mass index. AJOG 209(6):562.e1–5
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21. Sekhavat Leila, Fallah Razieh (2013) Could maternal pre-pregnancy body mass index affect Apgar score? Arch Gynecol Obstet 287:15–18 22. Jozwiak M, Bloemenkamp KW, Kelly AJ, Mol BW, Irion O, Boulvain M (2012) Mechanical methods for induction of labour. Cochrane Database Syst Rev 3:CD001233 23. Gelber S, Sciscione (2006) Mechanical methods of cervical ripening and labor induction. Clin Obstet Gynecol 49:642–657 24. Delaney S, Shaffer BL, Cheng YW, Vargas J, Sparks TN, Paul K et al (2010) Labor induction with a Foley balloon inflated to 30 mL compared with 60 mL: a randomized controlled trial. Obstet Gynecol 115:1239–1245 25. Jozwiak M, Rengerink KO, Benthem M, van Beek E, Dijksterhuis MG, de Graaf IM, For the PROBAAT Study Group et al (2011) Foley catheter versus vaginal prostaglandin E2 gel for induction of labour at term (PROBAAT trial): an open-label, randomised controlled trial. Lancet 378:2095–2103 26. Cromi A, Ghezzi F, Uccella S, Agosti M, Serati M, Marchitelli G et al (2012) A randomized trial of preinduction cervical ripening: dinoprostone vaginal insert versus double-ballooncatheter. Am J Obstet Gynecol 207:125.e1–7 27. Mei-Dan E, Walfisch A, Valencia C, Hallak M (2014) Making cervical ripening EASI: a prospective controlled comparison of single versus double balloon catheters. J Matern Fetal Neonatal Med 27(17):1765–1770 28. Mei-Dan E, Walfisch A, Suarez-Easton S, Hallak M (2012) Comparison of twomechanical devices for cervical ripening: a prospective quasi-randomized trial. J Matern Fetal Neonatal Med 25:723–727 29. Saylawala MA, Horton A (2014) Effect of obesity on outcomes in nulliparous women undergoing balloon ripening for labor induction. Obstet Gynecol 123:77S–77S 30. Pevzner L, Powers BL, Rayburn WF, Rumney P, Wing DA (2009) Effects of maternal obesity on duration and outcomes of prostaglandin cervical ripening and laborinduction. Obstet Gynecol 114(6):1315–1321 31. Horton A, Diaz J, Mastrogiannis D (2014) Accuracy of estimated fetal weight by ultrasonography compared with the leopold maneuver and effect of maternal obesity. Obstet Gynecol 123(Suppl1):193S 32. LaCoursiere D, Barrett-Connor E, O’Hara M, Hutton A, Varner M (2010) The association between prepregnancy obesity and screening positive for postpartum depression. BJOG 117:1011– 1018
MATERNAL-FETAL MEDICINE
Mechanical labor induction in the obese population: a secondary analysis of a prospective randomized trial Saja Anabusi1 • Elad Mei-Dan1 • Mordechai Hallak1 • Asnat Walfisch1
Received: 22 February 2015 / Accepted: 26 May 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Objective The objective of this study was to estimate the influence of maternal body mass index (BMI) on progress and outcomes of labor induction using mechanical devices. Methods This study was a secondary analysis of data collected during the Cook Catheter vs. Foley Catheter study, a series of prospective randomized trials of women requiring cervical ripening for labor induction. The duration, characteristics, and outcomes of labor were analyzed after stratification by BMI categories. Outcomes assessed included time from device insertion to delivery, successful ripening, cesarean delivery rates, and any maternal and neonatal adverse events. Results One hundred and eighty-one patients were stratified according to BMI categories, with 102 study participants classified as normal weight (BMI B30) and 79 as obese (BMI [30). Maternal satisfaction from the induction process was significantly lower in the obese group compared to the normal weight group (5.95 ± 3.14 vs. 7.58 ± 2.7, respectively, in a 1–10 scale, p = 0.009). The cesarean delivery rate was similar in the normal weight and the obese groups (17.6 vs. 25.3 %, respectively, p = 0.27). No statistical differences were found in all other outcomes evaluated, including a sub-analysis of the different mechanical devices.
Presented in part at the 32nd Annual Meeting of the Society for Maternal–Fetal Medicine, Dallas, Texas, February 6–11, 2012. & Saja Anabusi [email protected] 1
Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, affiliated with the Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, P.O.B. 169, 38100 Hadera, Israel
Conclusions During the process of mechanical cervical ripening, maternal satisfaction, but not objective obstetrical parameters, was influenced by increased maternal BMI. The trial is registered at ClinicalTrials.gov, no: NCT00604487. Trial registry name is ‘‘Induction of Labor in Patients with Unfavorable Cervical Conditions.’’ Keywords Induction of labor Balloon Obesity Overweight
Introduction Obesity (Body Mass Index—BMI of [30 kg/m2) has become a worldwide epidemic in the last few decades with a prevalence that varies widely depending on the definition, location, genetics, and other demographic characteristics. In the United States, more than one-third of women are obese, and 8 % of reproductive aged women are extremely obese (BMI [40 kg/m2) [1]. Numerous studies suggest an association between obesity and pregnancy complications. Obesity is associated with anovulation and subfertility [2] as well as with poorer outcome of infertility treatment [3]. Additionally, obese women suffer from increased rates of miscarriages [4] and a variety of pregnancy complications [5–9]. Intra-partum complications and labor induction are also more common [5, 6, 10–16] as are postpartum complications [17–19], and BMI was found to be an independent predictor of cesarean delivery among nulliparous morbidly obese women [20]. Lastly, fetal and neonatal risks including low Apgar score, prematurity, stillbirth, congenital anomalies (neural tube defects—NTD), and childhood and adolescence obesity were reported to be associated with maternal obesity [6, 12, 21].
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Arch Gynecol Obstet
Labor induction is one of the most commonly performed obstetrical interventions. Although multiple methods for cervical ripening and labor induction exist, the search for the optimal method is ongoing. Mechanical methods for cervical ripening, specifically cervical balloon catheters, have the advantage of ripening the cervix without inducing simultaneous uterine contractions [22–24]. Moreover, mechanical methods have been repeatedly shown to be as effective as pharmacological methods in cervical ripening [24, 25] with comparable or even higher vaginal delivery rates [26]. This study is a secondary analysis of two previously published randomized controlled trials, conducted by our group, comparing mechanical devices for cervical ripening. In this sub-analysis, we focused on the possible effect of maternal BMI on the progress and outcomes of cervical ripening and labor induction performed using different mechanical devices [27, 28].
Methods This study is a secondary analysis of data collected during the Cook Catheter vs. Foley Catheter Study [27, 28], a series of prospective randomized trials involving women requiring cervical ripening using different mechanical techniques for cervical ripening. The study was conducted between November 2007 and Jan 2011 at the Hillel Yaffe Medical Center, Hadera, Israel. The study was approved by the local institutional review board. The studies’ protocols are detailed elsewhere [27, 28] and are summarized here. We included patients with a singleton pregnancy in a vertex presentation with intact membranes at term (37 completed weeks or more). Eligible women were planned for induction of labor for various indications, and all had an unfavorable cervix (Bishop score B4). We excluded women with contraindications for a vaginal delivery (i.e., placenta previa, non-vertex presentation), presence of ruptured membranes, presence of a uterine scar, and suspected fetal distress necessitating immediate intervention. Eligible women were given an explanation as well as an information sheet followed by an informed consent form. Prior to randomization, we collected data on the patients’ medical and gynecological history, physical and vaginal examination, initial Bishop score, ultrasonography for fetal position and weight estimation, and the biophysical profile score. A suitable patient was one who met all the inclusion criteria specified above and signed the informed consent form. Following randomization, either a Foley catheter or the Cook cervical ripening balloon catheter (with or without EASI) was inserted into the cervical canal. Specific considerations of the insertion technique are detailed elsewhere [27, 28].
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Following the insertion of either device, a 30-min nonstress test monitoring was completed. All participants rated the pain associated with the catheter insertion procedure using a visual analog scale (0–10, 0 = no pain, 10 = worst possible pain). Balloon expulsion was regularly monitored by the medical team and in any case of a change in reported symptoms. Twelve hours after insertion of the device, if not spontaneously expelled, the balloons were deflated, and the device was removed. Immediately following balloon expulsion or removal, the Bishop score was reassessed. Induction of labor was commenced in any of the following cases which were considered to be successfully ripened: second Bishop score increases by two points or more or a cervical dilation of 3 cm or more. Methods of labor induction included intravenous administration of oxytocin and/or artificial rupture of the membranes. Standardized oxytocin and labor induction protocols were followed in all cases. In all other cases, failure of the method used to ripen the cervix was declared, and the patient was re-evaluated for a different cervical ripening/labor induction method according to the obstetrical circumstances (most commonly using vaginal prostaglandins E1 or E2). Active labor was defined as cervical dilatation of 4 cm or more in the presence of regular uterine contractions. The primary outcome of the original trials was time from device insertion to delivery. Secondary outcomes included successful ripening rate, cesarean delivery rate, any occurrence of maternal or fetal adverse events, and maternal satisfaction from the induction process. Here, we assessed the cervical ripening and labor induction duration, mode of delivery, and feto-maternal outcomes, as well as maternal labor experience satisfaction. All these outcomes were stratified by different BMI categories. Statistical analysis For the original study, sample size was determined by Win Epi-scope 2 for independent samples. We anticipated a 20 % difference (0.5 SD) in the induction-to-delivery interval between the different devices. For a period of 4 years, we assigned all eligible women who presented for induction, on even months to the Cook cervical ripening balloon group and on odd months to the Foley catheter group. Analysis was performed according to the intention to treat principle. Data analysis was performed with the SPSS package version 15 (SPSS, Chicago, Illinois, USA). We divided the entire study population into 2 subgroups according to the body mass index (BMI): normal weight was defined as BMI B30, and obesity was defined as BMI [30. Descriptive statistics for continuous variables included mean, standard deviation, median, and percentiles. Differences in the continuous variables were
Arch Gynecol Obstet
performed by Student’s t test and the Mann–Whitney U test. Differences in the categorical variables were analyzed using the Chi-square test and the Fisher exact test. A p B 0.05 was considered statistically significant.
Results One hundred eighty-one patients were stratified according to BMI categories, with 102 classified as normal weight (BMI B30) and 79 classifiedas obese [BMI [30, Study flow chart (Fig. 1)]. There was no difference in mean BMI values between the different mechanical device groups, including: double-balloon catheter, Foley catheter with EASI, or double-balloon catheter with EASI (30.26 ± 5.2, 29.83 ± 5.5, 29.47 ± 4.7, p = 0.38) respectively. In addition, rates of obese women (BMI [30) in the double-balloon catheter, double-balloon catheter with EASI, and Foley catheter with EASI groups were comparable (44.8, 33.3, 44.3 %, respectively, p = 0.7). Patients’ demographic characteristics did neither differ in the two groups (Table 1) nor did the indications for labor induction (Table 1). Additionally, there were no differences in fetal assessment before labor induction except for estimated fetal weight prior to delivery. The Bishop score prior to balloon insertion or following its expulsion did not differ between the groups (Table 2), and there was no difference in the reported technical difficulty or in the patients’ reported discomfort (Table 2). Assesed for eligibality n=286 Data on BMI (n=181) 63.3%
Missing BMI data (n=105) 36.7%
BMI≤30 (n=102)
BMI>30 (n=79)
56.4%
43.6%
48a (47%)
39 a(49.4%)
Double ballon catheter
Double ballon catheter
44 a,b(43.2%)
35 a,b(44.3%)
Foley catheter with EASI
Foley catheter with EASI
10 b (9.8%)
5a (6.3%)
Double ballon catheter with EASI
Double ballon catheter with EASI
Fig. 1 Study flow chart: aMei-Dan et al. [27], bMei-Dan et al. [28]
Following either balloon insertion, there were no differences between the groups in ripening success, balloon insertion to delivery interval, time to expulsion, or mode of delivery (Table 2). Although no differences were noted in almost all primary and secondary obstetrical outcomes assessed, obese women were significantly less satisfied from the labor induction process, compared to the normal weight group (5.95 ± 3.1 vs. 7.58 ± 2.7, respectively, in a 1–10 scale, p = 0.009). Regarding fetal outcomes, there were no significant differences in neonatal mean birth weights or Apgar scores (Table 2).
Discussion Our results show that the process of mechanical cervical ripening was not affected by maternal obesity. Following stratification of the study participants into two BMI categories, no differences were noted in ripening success, induction length, or mode of delivery. In previous studies, BMI was found to be an independent predictor of cesarean delivery among nulliparous morbidly obese women [20]. For example, Saylawala et al. [29] retrospectively studied a cohort of 502 nulliparous women undergoing induction of labor at term, using balloon cervical ripening. He found cesarean delivery rate to be significantly higher in the obese subgroup compared with non-obese women (54.9 % compared with 37.9 %, p = 0.001). Another example is the secondary analysis, published by Pevzner et al. [30], of the data collected during the Misoprostol Vaginal Insert trail. Here too, patients were stratified according to BMI categories, and the incidence of cesarean delivery was examined. The rate of cesarean delivery increased with the BMI. In our study, there were no differences in the mode of delivery between the groups. Possibly, this is a result of a smaller study size and a lower degree of obesity in our study population. Another point is the method of cervical ripening used in our study. All women in both groups underwent pre-induction cervical ripening by a mechanical device (either double-balloon catheter or Foley, with or without EASI) as opposed to a pharmacological method. We suspect that our results can testify to a potential superiority of mechanical cervical ripeners compared to pharmacological methods specifically in the obese population. Theoretically, mechanical cervical ripening in obese women may be superior to pharmacological agents due to the different nature of these two interventions with the mechanical method being more independent of maternal weight. A significant difference between the two groups was the estimated fetal weight prior to delivery. Obese women were estimated to have heavier fetuses than lean
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Arch Gynecol Obstet Table 1 Demographic Characteristics and Baseline Fetal Assessment
Characteristics
BMI B30 (n = 102)
BMI [30 (n = 79)
p value
Maternal age (year)
28.03 ± 5.5
28.76 ± 5.5
0.38
Family status (% married)
97 (95.1 %)
78 (98.7 %)
0.28
Gestational age upon enrollment (week)
39.48 ± 2.0
39.57 ± 1.7
0.76
43 (42.6 %)
26 (32.9 %)
0.22
Ethnic origin (%) Native Israeli Arabic
41 (40.6 %)
40 (50.6 %)
0.22
Nulliparity (%)
54.5
47.4
0.36
Grand-multiparitya (%)
5
7.7
0.53
Elementary school
5 (5.6 %)
9 (13.2 %)
0.15
High school
46 (51.1 %)
37 (54.4 %)
0.74
University
39 (43.3 %)
22 (32.4 %)
0.24
86 (85 %)
59 (76 %)
0.12
14 (13.7 %)
18 (24 %)
Post-datec
13 (22 %)
19 (24 %)
Pre-eclampsia
10 (10 %)
9 (11 %)
0.81
NRFHRd monitoring
23 (22 %)
12 (15 %)
0.26
Diabetes
10 (10 %)
11 (14 %)
0.48
Oligohydramnione
30 (29 %)
31 (39 %)
0.20
Other
32 (31 %)
32 (31 %)
0.24
Fetal estimated weight (gr)
3200 (1374–4130)
3293 (1606–4300)
0.026
Amniotic Fluid Index (AFI) (cm, median, range)
7.5 (0–31)
4 (0–43)
0.5
Normal Non-Stress Test (%)
83 (81.4)
67 (84.8)
0.69
Contractions upon admission
28 (27.5)
14 (17.7)
0.15
Education (%)
General medical history (%) No known illness Otherb Indication for labor induction
0.86
Primary fetal assessment
Data are in numbers (valid %) or mean ± SD a
Grand-multiparity [4 deliveries
b
Other—including diabetesmellitus, hypertension, asthma, chronic infectious diseases, ischemic heart disease, thyroid dysfunction, and other
c
Defined as [40 completed weeks of gestation
d
NRFHR—Non-reassuring fetal heart rate
e
Defined as less than 5 cm amniotic fluid index
women, (3200 vs. 3293, respectively, p = 0.026) although the actual birth weight was virtually the same (3145 vs. 3195 gr p = 0.29). This difference maybe a result of the technical challenge involved in clinical and sonographic assessment of fetal weight in the obese population [31]. Our results showed differences in the satisfaction rates between the groups, with the obese women reporting less satisfaction from the process, compared with the normal BMI group. Of note is the fact that the obese women did neither report more pain during the insertion process (3.57 ± 2.4 vs. 3.26 ± 2.2, p = 0.54) nor did the physician report more difficulty in the insertion (80.7 vs. 76.8 %,
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p = 0.55), and thus this cannot explain the lower satisfaction rate. In an attempt to explain the lower satisfaction rate in the obese group, unrelated to any objective outcomes assessed, we assume that this relates to maternal emotional state. It is well established that depression is more common in the obese population in general and in pregnancy and the post-partum period as well [31]. LaCoursiere et al. [32] have screened 1053 women for post-partum depression, stratified by BMI. Roughly, 15 % of normal weight women screened positive for postpartum depression, and depression rates increased progressively as BMI increased (p \ 0.01). We suspect that this may have to do with the lower satisfaction rates in the obese
Arch Gynecol Obstet Table 2 Balloon Insertion and Labor Outcome Outcomes
BMI B30 n = 102 (valid %)
BMI [30 n = 79 (valid %)
p value
Bishop score before balloon insertion (median, range)
2.49 (0–4)
2.42 (0–4)
0.71
Bishop score after balloon expulsion (median, range)
6.5 (2–9)
6.45 (3–9)
0.82
Spontaneous balloon expulsion (valid %)
35 (34.7)
25 (32.1)
0.75
Difficulty during balloon insertion
a
72 (80.9)
53 (76.8)
0.55
Pain perception during catheter insertion (VAS range 1–10, mean ± SD)
No difficulty (valid %)
3.57 ± 2.4
3.26 ± 2.2
0.54
Ripening successb
98.0
94.9
0.41
Spontaneous rupture of membranes
37 (44)
39 (60.9)
0.04
Balloon insertion todelivery time (median, hours:minutes)
16:00
16:57
0.092
Insertion to expulsion (median, hours:minutes)
11:15
11:30
0.19
Delivery mode VD, n (%) CS, n (%) Birthweight (gr) (mean ± SD) Use of analgesia
c
84 (82.4)
59 (74.6)
0.16
18 (17.6)
20 (25.3)
0.27
3145 ± 596
3195 ± 488.6
0.29
86 (86.9)
69 (90.8)
0.48
Total hospitalization (mean in days ± SD)
6.11 ± 5.5
5 ± 3.885
0.76
Maternal satisfaction (VAS range 1–10, mean ± SD)
7.58 ± 2.7
5.95 ± 3.1
\0.01
1 min
9 (0–10)
9(4–10)
0.16
5 min
10 (7–10)
10 (6–10)
0.58
Apgar score (0–10)
a
Rated by the caregiver: 1—no difficulty at all, 5—extremely difficult
b
Successful ripening defined as second Bishop score increases by two or more points or cervical dilatation of 3 cm or more
c
Of any type including Epidural or Pethidine or both
subgroup of our study although depression was not assessed in our study population. Our study’s main strength lies in its prospective randomized design, and the fact that both obese and normal weight women demonstrated comparable demographic characteristics. Although the study was originally randomized to three different mechanical ripening methods (the Cook ripening double-balloon catheter with or without EASI and the Foley catheter with EASI), the distribution of BMIs between the original study groups was similar, and thus we could disregard the type of balloon used in our analysis. The main weakness of our study lies in the fact that it is a sub-analysis of a previous study designed for a different purpose and different outcome measures. However, as the rates of obesity were similar in all 3 study arms, and the distribution of intervention in the obese and non-obese subgroups was virtually the same, we feel this point did not bias our results. In summary, our study demonstrates that except for a lower mean maternal satisfaction rate, mechanical cervical ripening as a part of labor induction is not influenced by increased maternal BMI. As obesity is a major challenge in modern obstetrics, further studies are needed to corroborate
our results and better define the optimal cervical ripening and labor induction methods to be used in the maternal obese sub-population. Conflict of interest
The authors report no conflict of interests.
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