Concurrent versus sequential methods for labor induction at term

Concurrent versus sequential methods for labor induction at term

International Journal of Gynecology and Obstetrics (2007) 96, 94–97 a v a i l a b l e a t w w w. s c i e n c e d i r e c t . c o m w w w. e l s e v i...

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International Journal of Gynecology and Obstetrics (2007) 96, 94–97 a v a i l a b l e a t w w w. s c i e n c e d i r e c t . c o m

w w w. e l s e v i e r. c o m / l o c a t e / i j g o

CLINICAL ARTICLE

Concurrent versus sequential methods for labor induction at term R.A. Khan a,⁎, Z.E. Khan a , O. Ashraf b a b

Department of Obstetrics and Gynecology, Aga Khan University Hospital, Stadium Road, Karachi, Pakistan Medical College, Aga Khan University Hospital, Stadium Road, Karachi, Pakistan

Received 30 April 2006; received in revised form 29 September 2006; accepted 4 October 2006

KEYWORDS Labor; Oxytocin; Prostaglandins

Abstract Objective: To determine the efficacy and safety of the concurrent administration of oxytocin and prostaglandin E2 (PGE2) for induction of labor at term, prompt delivery, and good maternal and neonatal outcomes. Methods: In this comparative cohort study of 70 women conducted in Pakistan, 35 were given oxytocin and PGE2 concurrently and 35 were given the drugs sequentially for labor induction. Two-sample t tests and ×2 tests were used for the evaluation of continuous and categorical data, respectively. Results: The mean induction to delivery time was shorter by 2.4 h in the concurrent treatment group (P < 0.001), and the proportion of vaginal deliveries was higher in that group. Conclusion: The concurrent method of induction of labor resulted in shorter induction to delivery time and a higher proportion of vaginal deliveries. © 2006 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

1. Introduction Induction of labor is one of the most prevalent obstetrical interventions. The decision to induce labor, especially in nulliparas with an unfavorable cervix, should be made with careful consideration of the risks associated with cesarean delivery. Desired outcomes are healthy mothers and newborns, along with reasonable efficiency of time, labor, and expense. Perspectives and priorities may be different when

⁎ Corresponding author. c/o Dr. K. Ashraf, Consultant Radiologist, X-Ray & Diagnostic Imaging, James Paget University Hospitals, Lowestoft Road, Gorleston, Great Yarmounth NR31 6LA, United Kingdom. Tel.: +44 1493 603001; fax: +44 1801 2866861. E-mail address: [email protected] (R.A. Khan).

confronted with questions of costs, risks, and benefits. Historically, labor induction has often involved pharmacologic or obstetric interventions to promote cervical softening and shorten labor duration. The results of recent comparative trials have not consistently shown one labor induction regimen to be clinically superior over another, however, and the art of successful labor induction lies in individualizing single or combination regimens. While nonpharmacologic methods for cervical maturation and/or labor induction–including such techniques as mechanical dilatation, stripping of the membranes, and amniotomy– may be efficient in some cases, they increase not only patient discomfort but also the risk of cesarean delivery, and their safety has been questioned [1–3]. Therefore, the use of pharmacologic agents has often been deemed necessary to establish a satisfactory safety to efficacy ratio [2–4].

0020-7292/$ - see front matter © 2006 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijgo.2006.10.002

Concurrent versus sequential methods for labor induction at term Oxytocin is a potent uterotonic agent, capable of stimulating uterine contractions at intravenous infusion rates of 1 to 2 mU per minute in women with pregnancies at term [5]. Although oxytocin is a safe and effective initiator of uterine contractions, success is contingent on the condition of the cervix at the beginning of labor induction. Prostaglandin E2 (PE2) preparations have gained wide acceptance for preinduction cervical ripening, as they have a good fetus safety profile and their administration is easy [6]. Various combinations involving timing and dosage for separate and simultaneous use of oxytocin and a PGE2 analogue for induction of labor are being tried for their ability to reduce induction to delivery time and increase the rate of vaginal deliveries without causing maternal or fetal adverse effects. The present study was based on the hypothesis that, in pregnant women at term, the concurrent administration of the PGE2 analogue dinoprostone and oxytocin results in shorter induction to delivery time and a higher proportion of vaginal deliveries than the sequential administration of dinoprostone and oxytocin.

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sive uterine activity associated with tachysystole (defined as 6 or more uterine contractions per 10-min intervals) or hypertonus (defined as a uterine contraction lasting for 2 or more minutes), associated with an abnormal fetal heart pattern warranting either of the following: stopping the oxytocin infusion; turning the patient to the left side; infusing a bolus of 500 mL of crystalloid solution; and/or administering oxygen by nasal cannula or mask. Neonatal complications were defined as low Apgar scores and admission to the neonatal intensive care unit. Analysis was performed using the Statistical Package for the Social Sciences, release 10.1 (SPSS Inc., Chicago, Illinois, USA). The anonymity of the participants was maintained through data collection, entry, and analysis. The study received approval from the institutional ethical review committee. Continuous data were expressed as mean ± S.D. and were analyzed with 2-sample t tests, categorical data were analyzed with ×2 tests, and P < 0.05 was considered to be statistically significant.

3. Results 2. Patients and methods This comparative cohort study was carried out with 70 women at a tertiary care hospital in Pakistan over 1 year. All women were primigravidas with singleton pregnancies of at least 36 weeks' duration; vertex presentation; and a Bishop score of 6 or less. Exclusion criteria were vaginal bleeding; more than 2 uterine contractions per 10-min interval; hypersensitivity to prostaglandins; intrauterine growth retardation; and any contraindication to induction of labor. All women gave informed consent. Two groups of 35 patients each were formed. An intracervical extra-amniotic catheter was inserted in all study participants the previous night to promote cervical ripening. The 35 women in the concurrent administration group received at the same time oxytocin and a vaginal pessary containing dinoprostone (Prepidil; Pharmacia and Upjohn, Kalamazoo, Michigan, USA). The 35 women in the sequential administration group first received pessaries containing the PGE2 analogue and then oxytocin, with an interval of at least a 4 h between insertion of the last dinoprostone-containing pessary and oxytocin administration). The time of insertion of the first pessary was considered the starting point of the induction. The sequential, rather than the concurrent use of prostaglandin and oxytocin, is part of the established protocol at this obstetrics unit. Arrest of labor was defined as a first stage longer 24.7 h or a second stage longer than 2 h in nulliparas, and a first stage longer 18.8 h or a second stage longer than 1 h in multiparas. A sample size of 70 was obtained on the basis of a predefined 1-year period, during which all women who met the selection criteria and gave informed consent were included in the study. The women were not randomly assigned to either group. Instead, they were consecutively included alternatively in the concurrent or the sequential treatment group. The primary outcome was induction to delivery time. Secondary outcomes were occurrence of uterine hyperstimulation, incidence of vaginal and abdominal delivery, and neonatal outcome. Hyperstimulation was defined as exces-

There were no differences between the 2 groups regarding maternal age, pregnancy duration, and preinduction Bishop scores. In both groups, labor was induced because of postdate pregnancy, hypertensive disorders during pregnancy, or premature rupture of membranes, or because epidural analgesia was available. In the sequential group, 3 women underwent induction of labor because of oligohydramnios. The mean induction to delivery time was 6.16 h in the concurrent treatment group and 8.55 h in the sequential treatment group. In other words, the mean induction to delivery time was 2.40 h or 144 min shorter in the concurrent than in the sequential treatment group (369 vs. 513 min; P < 0.001). Women who underwent the concurrent method of labor induction were more likely to be delivered vaginally than those in the sequential group (91.4% vs. 60%). The cesarean delivery rate was much lower in the concurrent than in the sequential treatment group (8.5% vs. 40%). Of the 14

Table 1 Outcome variables for 70 women undergoing concurrent or sequential pharmacologic labor induction with dinoprostone and oxytocin a Outcome

Concurrent Sequential method method (n = 35) (n = 35)

Induction to delivery time, h† Cesarean delivery Vaginal delivery Spontaneous Instrumental Uterine hyperstimulation Neonatal referrals to the neonatal intensive care unit

6.16 ± 2.00 3 (8.50) 32 (91.40) 26 6 0 0

8.55 ± 2.60 14 (40.00) 21 (60.00) 17 4 1 0

†P < 0.001. a Values are given as number, number ± S.D., or number (percentage).

96 cesarean sections in the sequential treatment group, 10 were performed for failure of labor to progress. Although the small sample size provides insufficient power to obtain a statistical difference between the cesarean delivery rates, failure of labor to progress might have been responsible for the higher rate in the sequential treatment group. There was no case of uterine hyperstimulation in the concurrent treatment group and 1 case in the sequential treatment group. Neonatal outcomes were equally favorable in the 2 groups. All newborns had Apgar scores higher than 7, and there was no referral to the neonatal intensive care unit in either group. Outcome variables are summarized in Table 1.

4. Discussion Although induction of labor is performed in approximately 20% to 30% of all pregnancies, and therefore is a frequent intervention [7,8], it remains a challenge for the obstetrician. In this study of concurrent or sequential pharmacologic induction of labor, all women with common indications for induction of labor were enrolled, and therefore the study population should be similar to that of any typical tertiary care facility. This comparative cohort study was carried out to determine whether there were differences in induction to delivery time and occurrence of fetal or maternal adverse effects between groups of women treated with a concurrent or sequential method of inducing labor with dinoprostone and oxytocin, with induction to delivery time as the primary outcome. It was hypothesized that the concurrent method led to shorter induction to delivery time without any adverse fetal or maternal effect. Although the incidence of fetomaternal morbidity caused by uterine hyperstimulation was reported to be similar whether women received a dinoprostone insert producing sustained drug release or dinoprostone gel intracervically [9], an obvious safety concern was uterine hyperstimulation. Yet, the present study clearly shows a clinical benefit to starting oxytocin infusion concurrently with the placement of a dinoprostone-containing vaginal pessary. In the concurrent treatment group labor duration was decreased by 2.40 h, no case of uterine hyperstimulation was encountered, and there were more than 91.4% of vaginal deliveries (compared with 60% in the sequential treatment group). The findings of this study are consistent with those reported by Coleman and colleagues [10], who found no case of uterine hyperstimulation when oxytocin was started immediately after the instillation of 0.5 mg of intracervical dinoprostone gel in 26 women. The administration of oxytocin concurrently with a sustained release of dinoprostone has been shown to decrease induction to delivery time and result in a higher proportion of vaginal deliveries without any fetal or maternal adverse effect [6]. Judged by published reports of its efficacy, the oxytocin/dinoprostone combination appears to be at least equivalent, or perhaps superior, to other induction methods. The major limitation of this study is that its small sample size (N = 70) does not provide sufficient power to obtain

R.A. Khan et al. definitive data concerning such important factors as the incidence of hyperstimulation or the cesarean delivery rate. With a baseline uterine hyperstimulation rate of 5% [11,12], a sample size of 1000 participants (500 in each treatment arm) would provide 80% power at a significance level of 0.05 and therefore be sufficient to detect a 5% increase in the hyperstimulation rate. With this sample size, a 7% decrease or 8% increase in the cesarean delivery rate could be ascertained. However, based on the experience reported by Coleman and colleagues [10], the number of women in each group in the present study was sufficient to detect a 6-h difference in the induction to delivery time with a 90% power and a 2tailed P value of 0.05. In summary, oxytocin administered concurrently with dinoprostone shortened induction to delivery time and resulted in higher proportion of vaginal deliveries without any adverse fetomaternal effects. Although the small sample size prevented definitive conclusions concerning important adverse effects that could be associated with concurrent treatment, it was adequate to detect a difference in induction to delivery time, which was the primary outcome variable in this study. This study shows that oxytocin administered concurrently with dinoprostone for labor induction at term significantly shortens induction to delivery time without causing any adverse effects. A mean decrease of 2.40 h was observed in the concurrent treatment group, in which no case of uterine hyperstimulation was observed. These findings are consistent with those of previous studies. In-patient cervical ripening procedures may be a psychological burden for pregnant women who require labor induction. Therefore, as long as no additional risk is detected, women and health care providers are likely to welcome the possibility that the concurrent administration of low-dose dinoprostone and oxytocin reduce induction to delivery time. Women with pregnancy-induced hypertension or meconium-stained liquor would especially welcome a shorter induction to delivery time. Although this study provides sufficient evidence of a decrease in induction to delivery time in the concurrent treatment group (P < 0.001), and add to the literature that has accumulated to show no increased incidence of hyperstimulation, its small sample size and low power do not allow to make definitive conclusions about the safety of the concurrent administration of dinoprostone and oxytocin for labor induction. More studies are needed to determine the safety of this method and whether it results in a higher proportion of vaginal deliveries than the conventional sequential method.

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