The epidemiology of labor induction: Arizona, 1997

The ARRIVE Trial

Timing of delivery such that maternal and perinatal outcomes are optimized is among the most important and commonplace decisions in obstetric care. Given the importance of this determination, it is somewhat surprising that there has been, until relatively recently, little in the way of high-quality evidence to guide obstetric clinicians in this decision. This chapter describes the evolution of studies examining the effects of labor induction and the importance of the ARRIVE trial in that context.

The role of labor induction in modern obstetrics

A primary goal of obstetrical practice is the optimization of maternal and perinatal health. This goal translates into a seemingly simple assessment with regard to considerations of the timing of delivery: delivery should occur when the benefits are greater than those of continued pregnancy. In the absence of an indication for cesarean delivery, planned delivery is initiated with induction of labor. When medical or obstetrical complications exist, they may guide recommendations regarding the timing of delivery. In the absence of these complications, gestational age also has been used to guide delivery timing, given its association with both maternal and perinatal adverse outcomes. If there is no medical indication, delivery before 39 weeks has been discouraged, given its association with greater chances of adverse perinatal outcomes. Conversely, it has been recommended that delivery occur by 42 weeks of gestation, given the perinatal risks that accrue in the post-term period. Historically, a 39-week induction of labor, particularly for individuals with no previous birth, has not been routinely offered in the absence of medical or obstetrical indications. That approach was based on numerous observational studies that demonstrated an increased risk of cesarean delivery and other adverse outcomes among individuals who underwent labor induction compared to those in spontaneous labor. However, from a management and person-centered-choice perspective, the relevant comparison is between those undergoing planned labor induction at a given time vs those planning to continue pregnancy beyond that time. When individuals have been compared using that rubric-either in observational studies or randomized trials that have been performed in a wide variety of locations and populations- there has not been evidence that induction increases adverse perinatal or maternal outcomes. Conversely, even when the only indication for delivery is the achievement of a full-term gestational age, evidence suggests that multiple different outcomes, including cesarean delivery, hypertensive disorders of pregnancy, neonatal respiratory impairment, and perinatal mortality, are less likely when induction is performed. This information underscores the importance of making the preferences of pregnant individuals for different birth processes and outcomes central to the approach to delivery timing.

Validating machine learning models for the prediction of labour induction intervention using routine data: a registry-based retrospective cohort study at a tertiary hospital in northern Tanzania

OBJECTIVES

We aimed at identifying the important variables for labour induction intervention and assessing the predictive performance of machine learning algorithms.

SETTING

We analysed the birth registry data from a referral hospital in northern Tanzania. Since July 2000, every birth at this facility has been recorded in a specific database.

PARTICIPANTS

21 578 deliveries between 2000 and 2015 were included. Deliveries that lacked information regarding the labour induction status were excluded.

PRIMARY OUTCOME

Deliveries involving labour induction intervention.

RESULTS

Parity, maternal age, body mass index, gestational age and birth weight were all found to be important predictors of labour induction. Boosting method demonstrated the best discriminative performance (area under curve, AUC=0.75: 95% CI (0.73 to 0.76)) while logistic regression presented the least (AUC=0.71: 95% CI (0.70 to 0.73)). Random forest and boosting algorithms showed the highest net-benefits as per the decision curve analysis.

CONCLUSION

All of the machine learning algorithms performed well in predicting the likelihood of labour induction intervention. Further optimisation of these classifiers through hyperparameter tuning may result in an improved performance. Extensive research into the performance of other classifier algorithms is warranted.

A Family-Based Study of the Association Between Labor Induction and Offspring Attention-Deficit Hyperactivity Disorder and Low Academic Achievement

The current study examined associations between labor induction and both (1) offspring attention-deficit hyperactivity disorder (ADHD) diagnosis in a Swedish birth cohort born 1992-2005 (n = 1,085,008) and (2) indices of offspring low academic achievement in a sub-cohort born 1992-1997 (n = 489,196). Associations were examined in the entire sample (i.e., related and unrelated individuals) with adjustment for measured covariates and, in order to account for unmeasured confounders shared within families, within differentially exposed cousins and siblings. We observed an association between labor induction and offspring ADHD diagnosis and low academic achievement in the population. However, these associations were fully attenuated after adjusting for measured covariates and unmeasured factors that cousins and siblings share. The results suggest that observed associations between labor induction and ADHD and low academic achievement may be due to genetic and/or shared environmental factors that influence both mothers' risk of labor induction and offspring neurodevelopment.

Investigating racial differences in risk factors for primary cesarean delivery

OBJECTIVE

The objective of the study was to investigate differences in sociodemographic, medical, and obstetric risk factors for primary cesarean delivery between black and white women.

STUDY DESIGN

We conducted a retrospective cohort study among 25,251 black and white women delivering a live, singleton infant with vertex presentation at a large, regional hospital between 2004 and 2010. Demographic and clinical data were derived from electronic hospital records. Differences in risk factors for primary cesarean delivery were analyzed using a modified Poisson regression approach stratified by race and parity.

RESULTS

Black and white women had a primary cesarean delivery rate of 24.7% and 22.2%, respectively (P < .001). Black women had an increased risk of cesarean delivery after adjusting for sociodemographic and clinical risk factors (adjusted relative risk [RR], 1.23; 95% confidence interval [CI], 1.17-1.29). Among nulliparas, labor induction had a greater effect on cesarean delivery for black women (adjusted RR, 1.32; 95% CI, 1.20-1.44) than for white women (adjusted RR, 1.13; 95% CI, 1.07-1.20). Among multiparas, labor induction reduced the risk of cesarean delivery for white women (adjusted RR, 0.63; 95% CI, 0.55-0.72), whereas no association was observed for black women (adjusted RR, 1.08; 95% CI, 0.92-1.28). Advanced maternal age was a stronger risk factor for black women (adjusted RR, 1.72; 95% CI, 1.43-2.08) than for white women (adjusted RR, 1.30; 95% CI, 1.11-1.52) among multiparas only. Among nulliparas, delivery at 37-38 weeks' gestation reduced the risk of cesarean delivery for black women (adjusted RR, 0.82; 95% CI, 0.73-0.92), whereas no association was observed for white women (adjusted RR, 0.96; 95% CI, 0.90-1.04).

CONCLUSION

Labor induction, among nulliparous women, and advanced maternal age, among multiparous women, are stronger risk factors for primary cesarean delivery for black women than for white women.

Moving toward patient-centered care: Women's decisions, perceptions, and experiences of the induction of labor process

BACKGROUND

Patient preferences and clinician practices are possible causative factors to explain the increase in induction of labor, but scientific studies that demonstrate this link are limited. The purpose of this study is to identify factors that influence inductions from the perspective of women.

METHODS

A qualitative investigation using grounded theory methodology was conducted. Women were interviewed preinduction and postinduction. Analysis of the interviews was conducted using constant comparison to identify codes, categories, and themes. Through this process the complex intersection between women, their clinician, and the application of evidence-based care in clinical practice was explored.

RESULTS

Five major themes from the preinduction interview were identified; safety of baby, women's trust in their clinician, relief of discomfort and/or anxiety, diminish potential or actual risk, and lack of informed decision making. Five major themes were identified from the postinduction interview; lack of informed decision making, induction as part of a checklist, women's trust in their clinician, happy with induction, and opportunities to improve the experience.

CONCLUSIONS

Lack of informed decision making was cited as a barrier to optimal care. This study has important implications for patient-centered research and clinical care, requiring the inclusion of women and the salient concepts of care that they identify.

Obstetric interventions for low-risk pregnant women in France: do maternity unit characteristics make a difference?

BACKGROUND

In many countries the closure of small maternity units has raised concerns about how the concentration of low-risk pregnancies in large specialized units might affect the management of childbirth. We aimed to assess the role of maternity unit characteristics on obstetric intervention rates among low-risk women in France.

METHODS

Data on low-risk deliveries came from the 2010 French National Perinatal Survey of a representative sample of births (n = 9,530). The maternity unit characteristics studied were size, level of care, and private or public status; the interventions included induction of labor; cesarean section; operative vaginal delivery (forceps, spatulas or vacuum); and episiotomy. Multilevel logistic regression analyses were adjusted for maternal confounding factors, gestational age, and infant birthweight.

RESULTS

The rates of induction, cesarean section, operative delivery, and episiotomy in this low-risk population were 23.9 percent, 10.1 percent, 15.2 percent, and 19.6 percent, respectively, and 52.0 percent of deliveries included at least one of them. Unit size was unrelated to any intervention except operative delivery (adjusted odds ratio [aOR] = 1.47 (95% CI, 1.10-1.96) for units with >3,000 deliveries per year vs units with <1,000). The rate of every intervention was higher in private units, and the aOR for any intervention was 1.82 (95% CI, 1.59-2.08). After adjustment for maternal characteristics and facility size and status, significant variations in the use of interventions remained between units, especially for episiotomies. Results for level of care were similar to those for unit size.

CONCLUSIONS

The concentration of births in large maternity units in France is not associated with higher rates of interventions for low-risk births. The situation in private units could be explained by differences in the organization of care. Additional research should explore the differences in practices between maternity units with similar characteristics.

Factors that influence the practice of elective induction of labor: what does the evidence tell us?

Elective induction of labor has been linked to increased rates of prematurity and rising rates of cesarean birth. The purpose of this investigation was to evaluate current trends in induction of labor scholarship focusing on evidence-based factors that influence the practice of elective induction. A key word search was conducted to identify studies on the practice of elective induction of labor. Analysis of the findings included clustering and identification of recurrent themes among the articles with 3 categories being identified. Under each category, the words/phrases were further clustered until a construct could be named. A total of 49 articles met inclusion criteria: 7 patient, 6 maternity care provider, and 4 organization factors emerged. Only 4 of the articles identified were evidence based. Patient factors were divided into preferences/convenience, communication, fear, pressure/influence, trust, external influences, and technology. Provider factors were then divided into practice preferences/convenience, lack of information, financial incentives, fear, patient desire/demand, and technology. Organization factors were divided into lack of enforcement/accountability, hospital culture, scheduling of staff, and market share issues. Currently, there is limited data-based information focused on factors that influence elective induction of labor. Despite patient and provider convenience/preferences being cited in the literature, the evidence does not support this practice.

Ethnicity and newborn outcomes: the case of African American women

PURPOSE

Although previous studies have confirmed the relationship between socioeconomic status, ethnicity, education, and occupation on birth outcomes, less is known about the relationship of providers influence or hospital characteristics on birth outcomes for minority women. It is not well understood whether hospital or physician characteristics exert an equal or greater affect compared with maternal sociodemographic factors, particularly for Black childbearing women known to be at particular risk for adverse birth outcomes.

DESIGN

This retrospective descriptive study sought to determine whether variation in neonatal birth outcomes for Black women was attributable to hospital characteristics, physician influence, or patient sociodemographics.

METHODS

Fixed and random effects were conducted to empirically determine the relative importance of hospital, physician, and patient characteristics (partitioning the variation of differences in birth outcome to each component) using a large administrative dataset.

FINDINGS

Considerable variability existed among hospitals over and above hospital ownership or number of hospital beds.

CONCLUSIONS

Ethnicity was a statistically significant predictor of adverse outcomes, as was the number of prenatal visits and maternal education. There is a significant relationship between adverse newborn outcomes and ethnicity after controlling for hospital and physician characteristics.

CLINICAL RELEVANCE

Ongoing birth disparities in African American childbearing women are a significant public policy issue with important research and clinical implications. This research adds to nursing knowledge by helping eliminate some factors previously thought to have contributed to the high incidence of perinatal complications for African American women and their newborns.

Elective induction versus spontaneous labour in Latin America

OBJECTIVE

To assess the frequency of elective induction of labour and its determinants in selected Latin America countries; quantify success in attaining vaginal delivery, and compare rates of caesarean and adverse maternal and perinatal outcomes after elective induction versus spontaneous labour in low-risk pregnancies.

METHODS

Of 37,444 deliveries in women with low-risk pregnancies, 1847 (4.9%) were electively induced. The factors associated with adverse maternal and perinatal outcomes among cases of spontaneous and induced onset of labour were compared. Odds ratios for factors potentially associated with adverse outcomes were calculated, as were the relative risks of having an adverse maternal or perinatal outcome (both with their 95% confidence intervals). Adjustment using multiple logistic regression models followed these analyses.

FINDINGS

Of 11,077 cases of induced labour, 1847 (16.7%) were elective. Elective inductions occurred in 4.9% of women with low-risk pregnancies (37,444). Oxytocin was the most common method used (83% of cases), either alone or combined with another. Of induced deliveries, 88.2% were vaginal. The most common maternal adverse events were: (i) a higher postpartum need for uterotonic drugs, (ii) a nearly threefold risk of admission to the intensive care unit; (iii) a fivefold risk of postpartum hysterectomy, and (iv) an increased need for anaesthesia/analgesia. Perinatal outcomes were satisfactory except for a 22% higher risk of delayed breastfeeding (i.e. initiation between 1 hour and 7 days postpartum).

CONCLUSION

Caution is mandatory when indicating elective labour induction because the increased risk of maternal and perinatal adverse outcomes is not outweighed by clear benefits.

The association between increased use of labor induction and reduced rate of cesarean delivery

AIM

An association was recently reported between a low cesarean section delivery rate and a method of obstetrical care that involved the frequent use of risk-guided prostaglandin-assisted preventive labor induction. We sought to confirm this finding in a subsequent group of pregnant women.

METHODS

A retrospective cohort study design was used to compare the outcomes of 100 consecutively delivered women, who were exposed to the alternative method of care, with the outcomes of 300 randomly chosen women who received standard management. The primary outcome was group cesarean delivery rate. Secondary outcomes were rates of neonatal intensive care unit admission, low 1-minute Apgar score, low 5-minute Apgar score, and major perineal trauma.

RESULTS

Women exposed to the alternative method of obstetrical care had a higher induction rate (59% vs. 16.3%, p < 0.001), a more frequent use of prostaglandins for cervical ripening (32% vs. 13%, p < 0.001), and a lower cesarean delivery rate (7% vs. 20.3%, p = 0.002). Exposed women did not experience higher rates of other adverse birth outcomes.

CONCLUSIONS

Exposure to an alternative method of obstetrical care that used high levels of risk-driven prostaglandin-assisted labor was again associated with two findings: a lower group cesarean delivery rate and no increases in levels of other adverse birth outcomes. An adequately powered randomized controlled trial is needed to further explore this alternative method of care.

Factors and outcomes associated with the induction of labour in Latin America

OBJECTIVE

To describe the prevalence of labour induction, together with its risk factors and outcomes in Latin America.

DESIGN

Analysis of the 2005 WHO global survey database.

SETTING

Eight selected Latin American countries.

POPULATION

All women who gave birth during the study period in 120 participating institutions.

METHODS

Bivariate and multivariate analyses.

MAIN OUTCOME MEASURES

Indications for labour induction per country, success rate per method, risk factors for induction, and maternal and perinatal outcomes.

RESULTS

Of the 97,095 deliveries included in the survey, 11,077 (11.4%) were induced, with 74.2% occurring in public institutions, 20.9% in social security hospitals and 4.9% in private institutions. Induction rates ranged from 5.1% in Peru to 20.1% in Cuba. The main indications were premature rupture of membranes (25.3%) and elective induction (28.9%). The success rate of vaginal delivery was very similar for oxytocin (69.9%) and misoprostol (74.8%), with an overall success rate of 70.4%. Induced labour was more common in women over 35 years of age. Maternal complications included higher rates of perineal laceration, need for uterotonic agents, hysterectomy, ICU admission, hospital stay>7 days and increased need for anaesthetic/analgesic procedures. Some adverse perinatal outcomes were also higher: low 5-minute Apgar score, very low birthweight, admission to neonatal ICU and delayed initiation of breastfeeding.

CONCLUSIONS

In Latin America, labour was induced in slightly more than 10% of deliveries; success rates were high irrespective of the method used. Induced labour is, however, associated with poorer maternal and perinatal outcomes than spontaneous labour.

Does routine induction of labour at 41 weeks really reduce the rate of caesarean section compared with expectant management?

OBJECTIVE

It is contended that routine induction of labour at 41 completed weeks of gestation reduces, or at least does not increase, a woman's chance of Caesarean section (CS), compared with expectant management. We wanted to know if this was true in our own hospital.

METHODS

We performed a retrospective review of 1367 nulliparous women who had reached 41+0 weeks undelivered with a live, singleton, fetus with a cephalic presentation. The women comprised two non-randomized contemporaneous cohorts: in one group, expectant management was planned, and in the second group the intention was to induce labour at 41 weeks. The primary outcome measure was the rate of CS in each group.

RESULTS

Of 645 women in whom expectant management was planned, 17.7% delivered by CS. Of 722 women in whom induction of labour was planned, 21.3% delivered by CS (P = 0.09). Of the total of 907 women in whom expectant management was planned or who laboured spontaneously before planned induction could be carried out, 16.6% delivered by CS. Of 460 women in whom induction was planned and actually carried out, 25.4% delivered by CS (P = 0.001).

CONCLUSION

The contention that routine induction of labour at 41 weeks reduces a woman's chance of delivery by Caesarean section was not supported by the findings of our study. Inducing labour may actually increase the nulliparous woman's risk of delivery by CS.

Reduction of elective inductions in a large community hospital

OBJECTIVE

Our goal was to lower unplanned primary cesarean deliveries by reducing elective inductions.

STUDY DESIGN

To implement and sustain an induction management program, a committee of care providers reviewed induction rates. "Elective" and other categories were defined. An induction consent form was drafted. Consent compliance, induction rates, hours in labor and delivery and mode of delivery were evaluated. Outcomes were compared with historical data from 2 years earlier.

RESULTS

A total of 10,166 nulliparas and 9869 multiparas attempted vaginal deliveries. Elective inductions decreased significantly, from 4.3% to 0.8% in nulliparas and from 13% to 9.5% in multiparas. A longer time to delivery was seen for both nulliparas (5.2 hours) and multiparas (4 hours) with elective inductions. Unplanned primary cesarean delivery rates are significantly lower in spontaneously laboring women, compared with those induced.

CONCLUSION

A program aimed at reducing elective inductions was successfully implemented and sustained.

Active management of risk in nulliparous pregnancy at term: association between a higher preventive labor induction rate and improved birth outcomes

OBJECTIVE

The objective of the study was to determine whether exposure of nulliparous women to a high rate of preventive labor induction was associated with improvement in birth health.

STUDY DESIGN

A risk-scoring system was used to guide the frequent use of preventive labor induction in 100 nulliparous women. The birth outcomes of this group were compared with those of 352 nulliparous women who received usual care. Cesarean delivery was the primary study outcome. The Adverse Outcome Index and the rate of uncomplicated vaginal delivery were used to measure overall birth health.

RESULTS

The exposed group experienced a higher labor induction rate (48% vs 23.6%; P < .001), a lower cesarean rate (9% vs 25.8%; adjusted odds ratio, 0.36; P = .02), and better composite birth outcomes.

CONCLUSION

Exposure of nulliparous women to a high preventive induction rate was significantly associated with improvement in birth health. Prospective randomized trials are needed to further explore the utility of risk-guided preventive labor induction.

The active management of risk in multiparous pregnancy at term: association between a higher preventive labor induction rate and improved birth outcomes

OBJECTIVE

To determine whether exposure of multiparous women to a high rate of preventive labor induction was associated with a significantly lower cesarean delivery rate.

STUDY DESIGN

Retrospective cohort study involving 123 multiparous women, who were exposed to the frequent use of preventive labor induction, and 304 multiparous women, who received standard management. Rates of cesarean delivery and other adverse birth outcomes were compared in the 2 groups. Logistic regression controlled for confounding covariates.

RESULTS

The exposed group had a lower cesarean delivery rate (adjusted odds ratio, 0.09; 0.8% vs 9.9%; P = .02) and a higher uncomplicated vaginal delivery rate (odds ratio, 0.53; 78.9% vs 66.4%; P = .01). Exposure was not associated with higher rates of other adverse birth outcomes.

CONCLUSION

Exposure of multiparous women to a high rate of preventive labor induction was significantly associated with improved birth outcomes, including a very low cesarean delivery rate. A prospective randomized trial is needed to determine causality.

The impact of the active management of risk in pregnancy at term on birth outcomes: a randomized clinical trial

OBJECTIVE

The purpose of this study was to compare birth outcomes that result from the active management of risk in pregnancy at term (AMOR-IPAT) to those outcomes that result from standard management.

STUDY DESIGN

This was a randomized clinical trial with 270 women of mixed parity. AMOR-IPAT used preventive labor induction to ensure delivery before the end of an estimated optimal time of delivery. Rates of 4 adverse obstetric events and 2 composite measures were used to evaluate birth outcomes.

RESULTS

The AMOR-IPAT-exposed group had a similar cesarean delivery rate (10.3% vs 14.9%; P = .25), but a lower neonatal intensive care unit admission rate (1.5% vs 6.7%; P = .03), a higher uncomplicated vaginal birth rate (73.5% vs 62.8%; P = .046), and a lower mean Adverse Outcome Index score (1.4 vs 8.6; P = .03).

CONCLUSION

AMOR-IPAT exposure improved the pattern of birth outcomes. Larger randomized clinical trials are needed to explore further the impact of AMOR-IPAT on birth outcomes and to determine the best methods of preventive labor induction.

Complications of labor induction among multiparous women in a community-based hospital system

OBJECTIVE

The purpose of this study was to examine complications of labor induction compared to spontaneous labor in multiparas.

STUDY DESIGN

This was a retrospective cohort study of multiparous women with live, singleton pregnancies at term, who had no contraindications to labor or labor induction. Cesarean delivery was the primary outcome.

RESULTS

Of the study subjects, 7208 experienced spontaneous labor, 2190 underwent labor induction with oxytocin, and 239 underwent labor induction requiring cervical ripening agents. Oxytocin-induced multiparas were 37% more likely to require cesarean compared to those with spontaneous labor (OR, 1.37; 95% CI, 1.10-1.71) and nearly 3 times more likely to undergo cesarean when cervical ripening agents were used (OR, 2.82; 95% CI, 1.84-4.53). Women requiring cervical ripening were also 10 times more likely to spend more than 12 hours in labor than those with spontaneous labor.

CONCLUSION

Multiparas undergoing labor induction are at increased risk for obstetric complications compared to spontaneous labor.

Induction of labor in the absence of standard medical indications: incidence and correlates

BACKGROUND

Induction of labor is an increasingly common obstetrical procedure, with approximately 20-34% of women undergoing labor induction in the United States annually.

OBJECTIVE

To determine the extent of labor induction in the absence of standard medical indications and to assess possible associations with maternal and infant characteristics and hospital factors.

METHODS

We ascertained induction of labor and associated details as part of a medical record validation study of 4541 women with live, singleton births in 2000 in Washington State using medical record, birth certificate, and hospital discharge data. In this analysis, we report findings for the 1473 women (33% of original cohort) whose medical records indicated that their labors were induced.

RESULTS

Among women with induced labor, 7.9% had no clinical information providing an indication for the induction, and 6.4% had only "nonstandard" indications recorded. Compared with women delivering in moderate volume hospitals, women who delivered at lower volume (odds ratios [OR] 3.9; 95% confidence intervals [CI] 1.8-8.6) or higher volume hospitals (OR 4.2; 95% CI 2.4-7.2) had significantly increased risk for undocumented indication of labor. Women who had undocumented indication for induction were at significantly decreased risk of giving birth at a teaching hospital and a public nonfederally owned hospital, and were at greater risk to give birth at a private religious hospital. Factors that remained independently associated with nonstandard indication for induction of labor were primiparas (OR 2.4; 95% CI 1.3-4.2); multiparas (OR 4.3; 95% CI 2.5-7.4), pregnancy-induced hypertension (OR 0.2; 95% CI 0.1-0.4), hospital volume >or=2000 births annually (OR 19.9; 95% CI 6.7-58.6), primary (OR 11.7; 95% CI 4.1-33.6), and tertiary level hospital (OR 0.4; 95% CI 0.2-0.7).

CONCLUSIONS

Our findings suggest that nearly 15% of inductions either were not clinically indicated according to standard protocols or indications were incompletely documented. At minimum, further studies are needed to explore how best to improve documentation of indications of labor because accurately describing, among other things, the process of labor induction, is a basic benchmark of care.

A preventive approach to obstetric care in a rural hospital: association between higher rates of preventive labor induction and lower rates of cesarean delivery

PURPOSE

Annual cesarean delivery rates in North America are increasing. Despite the morbidity associated with cesarean delivery, a safe preventive strategy to reduce the use of this procedure has not been forthcoming. During the 1990s, clinicians in a rural hospital developed a method of care involving prostaglandin-assisted preventive labor induction. An inverse relationship was noted between yearly hospital rates of labor induction and cesarean delivery. The purpose of our study was to compare cesarean delivery rates between practitioners who often used preventive induction and practitioners who did not, while controlling for patient mix and differences in practice style.

METHODS

Between 1993 and 1997, different hospital practitioners used risk-guided prostaglandin-assisted preventive labor induction with differing intensity. We used a retrospective cohort design, based on the practitioner providing prenatal care, to compare birth outcomes in women exposed to this alternative method of care with those in women not exposed. Multiple logistic regression analysis controlled for patient characteristics and clustering by practitioner.

RESULTS

The exposed group (n = 794), as compared with the nonexposed group (n = 1,075), had a higher labor induction rate (31.4% vs 20.4%, P <.001), a greater use of prostaglandin E2 (23.3% vs 15.7%, P <.001), and a lower cesarean delivery rate (5.3% vs 11.8%, P <.001). Adjustment for cluster effects, patient characteristics, and the use of epidural analgesia did not eliminate the significant association between exposure to this preventive method of care and a lower cesarean delivery rate. Rates of other adverse birth outcomes were either unchanged or reduced in the exposed group.

CONCLUSIONS

A preventive approach to reducing cesarean deliveries may be possible. This study found that practitioners who often used risk-guided, prostaglandin-assisted labor induction had a lower cesarean delivery rate without increases in rates of other adverse birth outcomes. Randomized controlled trials of this method of care are warranted.

Influence of parity on fetal mortality in prolonged pregnancy

OBJECTIVE

In England an estimated 50,000 inductions of labour at or beyond 41 weeks' gestation are conducted each year. However, the published evidence on the effect of parity on stillbirth in prolonged pregnancy is limited, and has produced conflicting data. The aim of this study is to evaluate the influence of parity on fetal mortality in prolonged pregnancies.

STUDY DESIGN

Retrospective analysis of 145,695 singleton births with known parity and no malformation noted at birth to residents in the former North-East Thames Region, UK. The parity and gestation specific stillbirth risks and relative risks per 1000 ongoing pregnancies were calculated in relation to parity between 37 and 45 weeks.

RESULTS

Before 41 weeks the stillbirth risk rose gradually but did not differ by parity. By 41 weeks there was a substantial increase in the stillbirth risk in nulliparous women but not in parous women. The pattern of rise is such that the stillbirth risk is 2.9 times higher (95% CI 1.06-8.19) in nulliparous women at >42 weeks' gestation.

CONCLUSION

Being parous appears to have a protective effect on fetal mortality in prolonged pregnancy. These findings question the need for routine induction of labour at 41 weeks in parous women.

Concurrent versus sequential methods for labor induction at term

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 x(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.

Socioeconomic Status and Receipt of Obstetric Services in Canada

OBJECTIVE

To examine differences in labor induction and cesarean delivery rates by socioeconomic status in Nova Scotia, Canada.

METHODS

We studied all women in Nova Scotia who delivered between 1988 and 1995 after a singleton pregnancy. Information was obtained from the Nova Scotia Atlee Perinatal Database and the federal income tax (T1) Family Files maintained by the Small Area and Administrative Data Division of Statistics Canada (n = 76,440). Labor induction and cesarean delivery rates were contrasted by family income and other indices, with adjustment for risk factors carried out using logistic models.

RESULTS

Maternal characteristics and other factors varied by socioeconomic status; in the lowest income group 4.4% of women were aged 35 years or older, and 49.4% were nonsmokers, whereas in the highest income group 17.7% were aged 35 years or older, and 88.7% were nonsmokers. Crude induction rates were similar across income groups (17.7% compared with 18.1% in the lowest compared with highest income groups), but there were significant differences in crude cesarean (17.7% compared with 21.2%) and crude primary cesarean rates (12.5% compared with 17.0%). Controlling for differences in risk factors altered these relationships. Adjusted rate ratios, 95% confidence intervals (CIs) and P values contrasting the lowest compared with highest income groups were labor induction 1.09 (95% CI 1.00-1.19), P = .05; overall cesarean delivery 1.12 (95% CI 1.03-1.23), P = .01; primary cesarean delivery 1.09 (95% CI 0.98-1.21), P = .12.

CONCLUSION

Affluent women in Canada are not more likely to have labor induction or cesarean delivery compared with less affluent women.

LEVEL OF EVIDENCE

II-2.

Active management of risk in pregnancy at term in an urban population: an association between a higher induction of labor rate and a lower cesarean delivery rate

OBJECTIVE

The purpose of this study was to determine whether exposure to an alternative method of care, called the active management of risk in pregnancy at term, was associated with a lower group cesarean delivery rate.

STUDY DESIGN

Active management of risk in pregnancy at term used risk factors for cesarean delivery to guide an increased use of labor induction. A retrospective cohort design was used to compare clinical outcomes of 100 pregnant women who were exposed to active management of risk in pregnancy at term to 300 randomly selected subjects who received standard management.

RESULTS

The 2 groups had comparable levels of prenatal risk. The group exposed to the active management of risk in pregnancy at term exposure group encountered a higher induction rate (63% vs 25.7%; P < .001) and a lower cesarean delivery rate (4% vs 16.7%; P = .01). Findings were similar for both nulliparous and multiparous subgroups. Active management of risk in pregnancy at term exposure was not associated with higher rates of other major birth outcomes.

CONCLUSION

Exposure to the active management of risk in pregnancy at term exposure was associated with a significantly lower group cesarean delivery rate. A prospective randomized trial that involved active management of risk in pregnancy at term exposure is needed to further explore this association.

Indicated labor induction with vaginal prostaglandin E2 increases the risk of cesarean section even in multiparous women with no previous cesarean section

AIMS

To evaluate the impact of induction of labor with vaginal tablets of prostaglandin E2 on the rate of cesarean section (CS), and to identify possible predictors of successful vaginal delivery.

METHODS

1541 consecutive women admitted for induction of labor with vaginal tablets of PGE2 were retrospectively compared with 574 consecutive women with spontaneous onset of labor.

RESULTS

Maternal age, nulliparity, previous CS, gestational age, and birth weight were similar in the study and control groups. The CS rate was twofold higher in the study group (20.7% vs 10.6%). CS rates in the study and control groups were 26.9% and 12.8% for the nulliparous women, and 11.2% and 5.1% for the multiparous women with no previous CS. Neither group had major maternal or fetal complications. A logistic regression model and stepwise analysis showed that nulliparity, previous CS, maternal age, number of PGE2 applications, birth weight, and the induction of labor by itself were independent significant risk factors for increased CS rate.

CONCLUSIONS

Induction of labor with vaginal PGE2 tablets results in a vaginal delivery rate of 79.3%, with apparently no serious maternal or fetal complications. Nulliparity, and previous CS are the most significant risk factors for increased CS rate. However, even after these risk factors are excluded and controlling for possible predictors for CS, PGE2 induction is independently associated with a twofold increase in CS rate, most often because of labor dystocia.

Labor induction rate variation in upstate New York: what is the difference?

BACKGROUND

Labor induction rates in the United States rose from 9.0 percent in 1989 to 20.5 percent in 2001, but reasons for the increase are poorly defined. A birth database from a region of upstate New York, including 31,352 deliveries from 1998 through 1999, was used to determine the degree of variation of labor induction rates among hospitals and practitioners.

METHODS

Total and elective labor induction rates were calculated for 16 hospitals and individual staff, and then evaluated using chi-square testing and regression.

RESULTS

Using all laboring women as the denominator, the regional labor induction rate was 20.8 percent; of these inductions, 25 percent had no apparent medical indication. Total induction rates and percent of elective inductions that were elective varied significantly among hospitals (10%-39% and 12%-55%, respectively, p<0.0001) and among practitioners within hospitals (7%-48% and 3%-76%, respectively, p<0.0001). Hospitals varied in size, risk status, and cesarean section rates, but these factors did not correlate with induction rates.

CONCLUSIONS

Labor induction rates are highly variable among and within hospitals. Delivery volume, population risk status, and differences in cesarean section rates did not explain this variation.

Induction of labor: the misoprostol controversy

Misoprostol (Cytotec) is safe and effective for induction of labor, although it is not approved by the Food and Drug Administration (FDA) for use in pregnancy. In August 2000, the manufacturer of misoprostol warned against its use in pregnancy because of its abortifacient properties and cited reports of maternal and fetal deaths when misoprostol was used to induce labor, fueling the misoprostol controversy. More than 45 randomized trials including more than 5400 women have found vaginal misoprostol to be more effective than oxytocin or vaginal prostaglandin E2 at effecting vaginal delivery within 24 hours. Cesarean delivery rates with vaginal misoprostol are lower than with oxytocin alone, but similar to prostaglandin E2. There have been no significant differences in the frequency of serious adverse maternal or neonatal outcomes with low-dose misoprostol compared with oxytocin or prostaglandin E2; however, the relative risk of rare adverse outcomes with misoprostol is unknown. The data suggest that absolute risks are low when misoprostol is used appropriately. We recommend 25 mcg vaginally every 4 to 6 hours for carefully selected patients in closely monitored settings. Whether misoprostol will prove to be the most cost-effective agent for inducing labor in women with an unfavorable cervix remains to be determined.

Trends and characteristics of induced labour in the United States, 1989-98

Induction of labour is one of the fastest growing medical procedures in the United States. In 1998, 19.2% of all US births were a product of induced labour, more than twice the 9.0% in 1989. Induction of labour has been efficacious in the management of post-term pregnancy and in expediting delivery when the mother or infant is sufficiently ill to make continuation of the pregnancy hazardous. However, the recent rapid increase in induction, and particularly the doubling of the induction rate for preterm pregnancies (from 6.7% in 1989 to 13.4% in 1998), has generated concern among some clinicians. The present study uses vital statistics natality data to examine the epidemiology of induced labour in the US. Multivariable analysis is used to examine the probability of having an induced delivery in relation to a wide variety of socio-demographic and medical characteristics, and also in relation to relative indications and contraindications for induced labour as outlined by the American College of Obstetricians and Gynecologists (ACOG). Induction rates were higher for women who were non-Hispanic white, college educated, born in the US, primaparae and those with intensive prenatal care utilisation. Induction rates were also higher for women with various medical conditions including hypertension, eclampsia and renal disease. For non-Hispanic white women with singleton births, 59% of the increase in the preterm birth rate from 1989 to 1998 can be accounted for by the increase in preterm inductions. The adjusted odds ratio for neonatal mortality among preterm births with induced labour was 1.20 [95% confidence interval 1.11, 1.31]. The rapid increase in induction rates, particularly among preterm births, marks a shift in the obstetric management of pregnancy. More detailed studies are needed to examine physician decision-making protocols, particularly for preterm induction, and to assess the impact of these practice changes on patient outcomes.

Outcome after elective labor induction in nulliparous women: a matched cohort study

OBJECTIVE

To determine whether elective induction of labor in nulliparous women is associated with changes in fetomaternal outcome when compared with labor of spontaneous onset.

STUDY DESIGN

All 80 labor wards in Flanders (Northern Belgium) comprised a matched cohort study. From 1996 through 1997, 7683 women with elective induced labor and 7683 women with spontaneous labor were selected according to the following criteria: nulliparity, singleton pregnancy, cephalic presentation, gestational age at the time of delivery of 266 to 287 days, and birth weight between 3000 and 4000 g. Each woman with induced labor and the corresponding woman with spontaneous labor came from the same labor ward, and they had babies of the same sex. Both groups were compared with respect to the incidence of cesarean delivery or instrument delivery and the incidence of transfer to the neonatal ward.

RESULTS

Cesarean delivery (9.9% vs 6.5%), instrumental delivery (31.6% vs 29.1%), epidural analgesia (80% vs 58%), and transfer of the baby to the neonatal ward (10.7% vs 9.4%) were significantly more common (P <.01) when labor was induced electively. The difference in cesarean delivery was due to significantly more first-stage dystocia in the induced group. The difference in neonatal admission could be attributed to a higher admission rate for maternal convenience when the women had a cesarean delivery.

CONCLUSION

When compared with labor of spontaneous onset, elective labor induction in nulliparous women is associated with significantly more operative deliveries. Nulliparous women should be informed about this before they submit to elective induction.

Randomized trial of concurrent oxytocin with a sustained-release dinoprostone vaginal insert for labor induction at term

OBJECTIVE

The purpose of this study was to determine whether the concurrent administration of oxytocin with sustained-release dinoprostone results in shorter induction times when compared with oxytocin after the removal of the dinoprostone insert.

STUDY DESIGN

Women with singleton pregnancies at > or = 36 weeks, vertex presentations, reactive nonstress tests, no prior uterine scar, intact membranes, and Bishop scores of < or = 6 were randomly assigned to receive oxytocin either immediately after placement of a sustained-release dinoprostone insert (immediate) or 30 minutes after its removal (delayed). The primary outcome was the time interval from induction to delivery.

RESULTS

Seventy-one patients were enrolled (immediate, 34 patients; delayed, 37 patients). There were no differences between treatment groups in non-reassuring fetal heart tracings, excess uterine activity, and epidural use. The mean time from dinoprostone placement until delivery was 544 minutes, shorter in the immediate group (972 vs 1516 minutes; P =.001). The proportion of deliveries within 24 hours was higher (90% vs 53%; P =.002) in the immediate group. Cesarean delivery rates were similar between the immediate and delayed groups (16% vs 13%; P =.73). No adverse maternal or neonatal outcomes were observed with concurrent therapy.

CONCLUSION

Oxytocin that is administered concurrently with sustained-release dinoprostone significantly shortens induction-to-delivery times and results in a higher proportion of vaginal deliveries of < or = 24 hours with no apparent adverse effects.