Prolonged pregnancy: the management debate

The history of labour induction: How did we get here?

The mean duration of human pregnancy is 280 days but the range is wide, and "term" has been defined to range from 37 to 42 weeks. In the 18th and 19th centuries, labour induction was used mainly in cases of pelvic deformity, before the foetus grew too large to be delivered. Induction methods were unreliable until the 20th century, when pituitary extract, and then synthetic oxytocin and prostaglandins, became available. "Disproportion" was the leading indication for induction until the 1950s, when it became clear that prolonged pregnancy was associated with increased perinatal mortality. Pregnancy dating was improved by ultrasound, which also showed that foetal growth slows at term. Induction rates rose during the 1970s, causing public concern about obstetric intervention. In the 21st century, large-scale randomised trials showed that perinatal mortality is lowest at 39-40 weeks, and that induction at that time does not increase the rate of operative delivery.

Induction of labour at or beyond 37 weeks' gestation

BACKGROUND

Risks of stillbirth or neonatal death increase as gestation continues beyond term (around 40 weeks' gestation). It is unclear whether a policy of labour induction can reduce these risks. This Cochrane Review is an update of a review that was originally published in 2006 and subsequently updated in 2012 and 2018.

OBJECTIVES

To assess the effects of a policy of labour induction at or beyond 37 weeks' gestation compared with a policy of awaiting spontaneous labour indefinitely (or until a later gestational age, or until a maternal or fetal indication for induction of labour arises) on pregnancy outcomes for the infant and the mother.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (17 July 2019), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) conducted in pregnant women at or beyond 37 weeks, comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour (expectant management). We also included trials published in abstract form only. Cluster-RCTs, quasi-RCTs and trials using a cross-over design were not eligible for inclusion in this review. We included pregnant women at or beyond 37 weeks' gestation. Since risk factors at this stage of pregnancy would normally require intervention, only trials including women at low risk for complications, as defined by trialists, were eligible. The trials of induction of labour in women with prelabour rupture of membranes at or beyond term were not considered in this review but are considered in a separate Cochrane Review.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

In this updated review, we included 34 RCTs (reporting on over 21,000 women and infants) mostly conducted in high-income settings. The trials compared a policy to induce labour usually after 41 completed weeks of gestation (> 287 days) with waiting for labour to start and/or waiting for a period before inducing labour. The trials were generally at low to moderate risk of bias. Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all-cause) perinatal deaths (risk ratio (RR) 0.31, 95% confidence interval (CI) 0.15 to 0.64; 22 trials, 18,795 infants; high-certainty evidence). There were four perinatal deaths in the labour induction policy group compared with 25 perinatal deaths in the expectant management group. The number needed to treat for an additional beneficial outcome (NNTB) with induction of labour, in order to prevent one perinatal death, was 544 (95% CI 441 to 1042). There were also fewer stillbirths in the induction group (RR 0.30, 95% CI 0.12 to 0.75; 22 trials, 18,795 infants; high-certainty evidence); two in the induction policy group and 16 in the expectant management group. For women in the policy of induction arms of trials, there were probably fewer caesarean sections compared with expectant management (RR 0.90, 95% CI 0.85 to 0.95; 31 trials, 21,030 women; moderate-certainty evidence); and probably little or no difference in operative vaginal births with induction (RR 1.03, 95% CI 0.96 to 1.10; 22 trials, 18,584 women; moderate-certainty evidence). Induction may make little or difference to perineal trauma (severe perineal tear: RR 1.04, 95% CI 0.85 to 1.26; 5 trials; 11,589 women; low-certainty evidence). Induction probably makes little or no difference to postpartum haemorrhage (RR 1.02, 95% CI 0.91 to 1.15, 9 trials; 12,609 women; moderate-certainty evidence), or breastfeeding at discharge (RR 1.00, 95% CI 0.96 to 1.04; 2 trials, 7487 women; moderate-certainty evidence). Very low certainty evidence means that we are uncertain about the effect of induction or expectant management on the length of maternal hospital stay (average mean difference (MD) -0.19 days, 95% CI -0.56 to 0.18; 7 trials; 4120 women; Tau² = 0.20; I² = 94%). Rates of neonatal intensive care unit (NICU) admission were lower (RR 0.88, 95% CI 0.80 to 0.96; 17 trials, 17,826 infants; high-certainty evidence), and probably fewer babies had Apgar scores less than seven at five minutes in the induction groups compared with expectant management (RR 0.73, 95% CI 0.56 to 0.96; 20 trials, 18,345 infants; moderate-certainty evidence). Induction or expectant management may make little or no difference for neonatal encephalopathy (RR 0.69, 95% CI 0.37 to 1.31; 2 trials, 8851 infants; low-certainty evidence, and probably makes little or no difference for neonatal trauma (RR 0.97, 95% CI 0.63 to 1.49; 5 trials, 13,106 infants; moderate-certainty evidence) for induction compared with expectant management. Neurodevelopment at childhood follow-up and postnatal depression were not reported by any trials. In subgroup analyses, no differences were seen for timing of induction (< 40 versus 40-41 versus > 41 weeks' gestation), by parity (primiparous versus multiparous) or state of cervix for any of the main outcomes (perinatal death, stillbirth, NICU admission, caesarean section, operative vaginal birth, or perineal trauma).

AUTHORS' CONCLUSIONS

There is a clear reduction in perinatal death with a policy of labour induction at or beyond 37 weeks compared with expectant management, though absolute rates are small (0.4 versus 3 deaths per 1000). There were also lower caesarean rates without increasing rates of operative vaginal births and there were fewer NICU admissions with a policy of induction. Most of the important outcomes assessed using GRADE had high- or moderate-certainty ratings. While existing trials have not yet reported on childhood neurodevelopment, this is an important area for future research. The optimal timing of offering induction of labour to women at or beyond 37 weeks' gestation needs further investigation, as does further exploration of risk profiles of women and their values and preferences. Offering women tailored counselling may help them make an informed choice between induction of labour for pregnancies, particularly those continuing beyond 41 weeks - or waiting for labour to start and/or waiting before inducing labour.

No. 214-Guidelines for the Management of Pregnancy at 41+0 to 42+0 Weeks

OBJECTIVE

To provide evidence-based guidelines for the management of pregnancy at 41+0 to 42+0 weeks.

OUTCOMES

Reduction of perinatal mortality associated with Caesarean section at 41+0 to 42+0 weeks of pregnancy.

EVIDENCE

The Medline database, the Cochrane Library, and the American College of Obstetricians and Gynecologists and the Royal College of Obstetricians and Gynecologists, were searched for English language articles published between 1966 and March 2007, using the following key words: prolonged pregnancy, post-term pregnancy, and postdates pregnancy. The quality of evidence was evaluated and recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care.

RECOMMENDATIONS

Induction of labour for improving birth outcomes for women at or beyond term

BACKGROUND

Beyond term, the risks of stillbirth or neonatal death increase. It is unclear whether a policy of labour induction can reduce these risks. This Cochrane review is an update of a review that was originally published in 2006 and subsequently updated in 2012 OBJECTIVES: To assess the effects of a policy of labour induction at or beyond term compared with a policy of awaiting spontaneous labour or until an indication for birth induction of labour is identified) on pregnancy outcomes for infant and mother.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (9 October 2017), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) conducted in pregnant women at or beyond term, comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour (expectant management). We also included trials published in abstract form only. Cluster-RCTs, quasi-RCTs and trials using a cross-over design are not eligible for inclusion in this review.We included pregnant women at or beyond term. Since a risk factor at this stage of pregnancy would normally require an intervention, only trials including women at low risk for complications were eligible. We accepted the trialists' definition of 'low risk'. The trials of induction of labour in women with prelabour rupture of membranes at or beyond term were not considered in this review but are considered in a separate Cochrane review.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

In this updated review, we included 30 RCTs (reporting on 12,479 women). The trials took place in Norway, China, Thailand, the USA, Austria, Turkey, Canada, UK, India, Tunisia, Finland, Spain, Sweden and the Netherlands. They were generally at a moderate risk of bias.Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all-cause) perinatal deaths (risk ratio (RR) 0.33, 95% confidence interval (CI) 0.14 to 0.78; 20 trials, 9960 infants; moderate-quality evidence). There were two perinatal deaths in the labour induction policy group compared with 16 perinatal deaths in the expectant management group. The number needed to treat to for an additional beneficial outcome (NNTB) with induction of labour in order to prevent one perinatal death was 426 (95% CI 338 to 1337). There were fewer stillbirths in the induction group (RR 0.33, 95% CI 0.11 to 0.96; 20 trials, 9960 infants; moderate-quality evidence); there was one stillbirth in the induction policy arm and 10 in the expectant management group.For women in the policy of induction arms of trials, there were fewer caesarean sections compared with expectant management (RR 0.92, 95% CI 0.85 to 0.99; 27 trials, 11,738 women; moderate-quality evidence); and a corresponding marginal increase in operative vaginal births with induction (RR 1.07, 95% CI 0.99 to 1.16; 18 trials, 9281 women; moderate-quality evidence). There was no evidence of a difference between groups for perineal trauma (RR 1.09, 95% CI 0.65 to 1.83; 4 trials; 3028 women; low-quality evidence), postpartum haemorrhage (RR 1.09 95% CI 0.92 to 1.30, 5 trials; 3315 women; low-quality evidence), or length of maternal hospital stay (average mean difference (MD) -0.34 days, 95% CI -1.00 to 0.33; 5 trials; 1146 women; Tau² = 0.49; I² 95%; very low-quality evidence).Rates of neonatal intensive care unit (NICU) admission were lower (RR 0.88, 95% CI 0.77 to 1.01; 13 trials, 8531 infants; moderate-quality evidence) and fewer babies had Apgar scores less than seven at five minutes in the induction groups compared with expectant management (RR 0.70, 95% CI 0.50 to 0.98; 16 trials, 9047 infants; moderate-quality evidence).There was no evidence of a difference for neonatal trauma (RR 1.18, 95% CI 0.68 to 2.05; 3 trials, 4255 infants; low-quality evidence), for induction compared with expectant management.Neonatal encephalopathy, neurodevelopment at childhood follow-up, breastfeeding at discharge and postnatal depression were not reported by any trials.In subgroup analyses, no clear differences between timing of induction (< 41 weeks versus ≥ 41 weeks' gestation) or by state of cervix were seen for perinatal death, stillbirth, NICU admission, caesarean section, or perineal trauma. However, operative vaginal birth was more common in the inductions at < 41 weeks' gestation subgroup compared with inductions at later gestational ages. The majority of trials (about 75% of participants) adopted a policy of induction at ≥ 41 weeks (> 287 days) gestation for the intervention arm.

AUTHORS' CONCLUSIONS

A policy of labour induction at or beyond term compared with expectant management is associated with fewer perinatal deaths and fewer caesarean sections; but more operative vaginal births. NICU admissions were lower and fewer babies had low Apgar scores with induction. No important differences were seen for most of the other maternal and infant outcomes.Most of the important outcomes assessed using GRADE had a rating of moderate or low-quality evidence - with downgrading decisions generally due to study limitations such as lack of blinding (a condition inherent in comparisons between a policy of acting and of waiting), or imprecise effect estimates. One outcome (length of maternal stay) was downgraded further to very low-quality evidence due to inconsistency.Although the absolute risk of perinatal death is small, it may be helpful to offer women appropriate counselling to help choose between scheduled induction for a post-term pregnancy or monitoring without (or later) induction).The optimal timing of offering induction of labour to women at or beyond term warrants further investigation, as does further exploration of risk profiles of women and their values and preferences. Individual participant meta-analysis is likely to help elucidate the role of factors, such as parity, in influencing outcomes of induction compared with expectant management.

Which method is best for the induction of labour? A systematic review, network meta-analysis and cost-effectiveness analysis

BACKGROUND

More than 150,000 pregnant women in England and Wales have their labour induced each year. Multiple pharmacological, mechanical and complementary methods are available to induce labour.

OBJECTIVE

To assess the relative effectiveness, safety and cost-effectiveness of labour induction methods and, data permitting, effects in different clinical subgroups.

METHODS

We carried out a systematic review using Cochrane methods. The Cochrane Pregnancy and Childbirth Group's Trials Register was searched (March 2014). This contains over 22,000 reports of controlled trials (published from 1923 onwards) retrieved from weekly searches of OVID MEDLINE (1966 to current); Cochrane Central Register of Controlled Trials (The Cochrane Library); EMBASE (1982 to current); Cumulative Index to Nursing and Allied Health Literature (1984 to current); ClinicalTrials.gov; the World Health Organization International Clinical Trials Registry Portal; and hand-searching of relevant conference proceedings and journals. We included randomised controlled trials examining interventions to induce labour compared with placebo, no treatment or other interventions in women eligible for third-trimester induction. We included outcomes relating to efficacy, safety and acceptability to women. In addition, for the economic analysis we searched the Database of Abstracts of Reviews of Effects, and Economic Evaluations Databases, NHS Economic Evaluation Database and the Health Technology Assessment database. We carried out a network meta-analysis (NMA) using all of the available evidence, both direct and indirect, to produce estimates of the relative effects of each treatment compared with others in a network. We developed a de novo decision tree model to estimate the cost-effectiveness of various methods. The costs included were the intervention and other hospital costs incurred (price year 2012-13). We reviewed the literature to identify preference-based utilities for the health-related outcomes in the model. We calculated incremental cost-effectiveness ratios, expected costs, utilities and net benefit. We represent uncertainty in the optimal intervention using cost-effectiveness acceptability curves.

RESULTS

We identified 1190 studies; 611 were eligible for inclusion. The interventions most likely to achieve vaginal delivery (VD) within 24 hours were intravenous oxytocin with amniotomy [posterior rank 2; 95% credible intervals (CrIs) 1 to 9] and higher-dose (≥ 50 µg) vaginal misoprostol (rank 3; 95% CrI 1 to 6). Compared with placebo, several treatments reduced the odds of caesarean section, but we observed considerable uncertainty in treatment rankings. For uterine hyperstimulation, double-balloon catheter had the highest probability of being among the best three treatments, whereas vaginal misoprostol (≥ 50 µg) was most likely to increase the odds of excessive uterine activity. For other safety outcomes there were insufficient data or there was too much uncertainty to identify which treatments performed 'best'. Few studies collected information on women's views. Owing to incomplete reporting of the VD within 24 hours outcome, the cost-effectiveness analysis could compare only 20 interventions. The analysis suggested that most interventions have similar utility and differ mainly in cost. With a caveat of considerable uncertainty, titrated (low-dose) misoprostol solution and buccal/sublingual misoprostol had the highest likelihood of being cost-effective.

LIMITATIONS

There was considerable uncertainty in findings and there were insufficient data for some planned subgroup analyses.

CONCLUSIONS

Overall, misoprostol and oxytocin with amniotomy (for women with favourable cervix) is more successful than other agents in achieving VD within 24 hours. The ranking according to safety of different methods was less clear. The cost-effectiveness analysis suggested that titrated (low-dose) oral misoprostol solution resulted in the highest utility, whereas buccal/sublingual misoprostol had the lowest cost. There was a high degree of uncertainty as to the most cost-effective intervention.

FUTURE WORK

Future trials should be powered to detect a method that is more cost-effective than misoprostol solution and report outcomes included in this NMA.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005116.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Vaginal prostaglandin (PGE2 and PGF2a) for induction of labour at term

BACKGROUND

Prostaglandins have been used for induction of labour since the 1960s. This is one of a series of reviews evaluating methods of induction of labour. This review focuses on prostaglandins given per vaginam, evaluating these in comparison with placebo (or expectant management) and with each other; prostaglandins (PGE2 and PGF2a); different formulations (gels, tablets, pessaries) and doses.

OBJECTIVES

To determine the effects of vaginal prostaglandins E2 and F2a for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment or other vaginal prostaglandins (except misoprostol).

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (1 March 2014) and bibliographies of relevant papers.

SELECTION CRITERIA

Clinical trials comparing vaginal prostaglandins used for third trimester cervical ripening or labour induction with placebo/no treatment, with each other, or other methods listed above it on a predefined list of labour induction methods.

DATA COLLECTION AND ANALYSIS

We assessed studies and extracted data independently.

MAIN RESULTS

Seventy randomised controlled trials (RCTs) (11,487 women) are included. In this update seven new RCTs (778 women) have been added. Two of these new trials compare PGE2 with no treatment, four compare different PGE2 formulations (gels versus tablets, or sustained release pessaries) and one trial compares PGF2a with placebo. The majority of trials were at unclear risk of bias for most domains.Overall, vaginal prostaglandin E2 compared with placebo or no treatment probably reduces the likelihood of vaginal delivery not being achieved within 24 hours. The risk of uterine hyperstimulation with fetal heart rate changes is increased (4.8% versus 1.0%, risk ratio (RR) 3.16, 95% confidence interval (CI) 1.67 to 5.98, 15 trials, 1359 women). The caesarean section rate is probably reduced by about 10% (13.5% versus 14.8%, RR 0.91, 95% CI 0.81 to 1.02, 36 trials, 6599 women). The overall effect on improving maternal and fetal outcomes (across a variety of measures) is uncertain.PGE2 tablets, gels and pessaries (including sustained release preparations) appear to be as effective as each other, small differences are detected between some outcomes, but these maybe due to chance.

AUTHORS' CONCLUSIONS

Prostaglandins PGE2 probably increase the chance of vaginal delivery in 24 hours, they increase uterine hyperstimulation with fetal heart changes but do not effect or may reduce caesarean section rates. They increase the likelihood of cervical change, with no increase in operative delivery rates. PGE2 tablets, gels and pessaries appear to be as effective as each other, any differences between formulations are marginal but may be important.

Does induction of labour increase the risk of caesarean section? A systematic review and meta-analysis of trials in women with intact membranes

BACKGROUND

Recent literature on the effect of induction of labour (compared with expectant management) has provided conflicting results. Reviews of observational studies generally report an increase in the rate of caesarean section, whereas reviews of post-dates and term prelabour rupture of membrane (PROM trials suggest either no difference or a reduction in risk.

OBJECTIVE

To evaluate with a systematic review and meta-analysis of randomised controlled trials (RCTs) whether or not the induction of labour increases the risk of caesarean section in women with intact membranes.

SEARCH STRATEGY

Literature search using electronic databases: MEDLINE, EMBASE, and the Cochrane Database of Clinical Trials.

SELECTION CRITERIA

RCTs comparing a policy of induction of labour with expectant management in women with intact membranes.

DATA COLLECTION AND ANALYSIS

A total of 37 trials were identified and reviewed. Quantitative analyses with fixed- and random-effects models were performed with revman 5.1.

MAIN RESULTS

Of the 37 RCTs, 27 were trials of uncomplicated pregnancies at 37-42 weeks of gestation. The remaining ten evaluated induction versus expectant management in pregnancies with suspected macrosomia (two), diabetes in pregnancy (one), oligohydramnios (one), twins (two), intrauterine growth restriction (IUGR) (two), mild pregnancy-induced hypertension (PIH) (one), and women with a high-risk score for caesarean section (one). Meta-analysis of 31 trials determined that a policy of induction was associated with a reduction in the risk of caesarean section compared with expectant management (OR 0.83, 95% CI 0.76-0.92).

AUTHOR'S CONCLUSIONS

Induction of labour in women with intact membranes reduces the risk of caesarean section. Review of the trials suggests that this effect may arise from non-treatment effects, and that additional trials are needed.

Induction of labour for improving birth outcomes for women at or beyond term

BACKGROUND

As a pregnancy continues beyond term the risks of babies dying inside the womb or in the immediate newborn period increase. Whether a policy of labour induction at a predetermined gestational age can reduce this increased risk is the subject of this review.

OBJECTIVES

To evaluate the benefits and harms of a policy of labour induction at term or post-term compared with awaiting spontaneous labour or later induction of labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 March 2012).

SELECTION CRITERIA

Randomised controlled trials conducted in women at or beyond term. The eligible trials were those comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour. Cluster-randomised trials and cross-over trials are not included. Quasi-random allocation schemes such as alternation, case record numbers or open random-number lists were not eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion. Two review authors independently assessed trial quality and extracted data. Data were checked for accuracy. Outcomes are analysed in two main categories: gestational age and cervix status.

MAIN RESULTS

We included 22 trials reporting on 9383 women. The trials were generally at moderate risk of bias.Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all-cause) perinatal deaths: risk ratio (RR) 0.31, 95% confidence interval (CI) 0.12 to 0.88; 17 trials, 7407 women. There was one perinatal death in the labour induction policy group compared with 13 perinatal deaths in the expectant management group. The number needed to treat to benefit (NNTB) with induction of labour in order to prevent one perinatal death was 410 (95% CI 322 to 1492).For the primary outcome of perinatal death and most other outcomes, no differences between timing of induction subgroups were seen; the majority of trials adopted a policy of induction at 41 completed weeks (287 days) or more.Fewer babies in the labour induction group had meconium aspiration syndrome (RR 0.50, 95% CI 0.34 to 0.73; eight trials, 2371 infants) compared with a policy of expectant management. There was no statistically significant difference between the rates of neonatal intensive care unit (NICU) admission for induction compared with expectant management (RR 0.90, 95% CI 0.78 to 1.04; 10 trials, 6161 infants). For women in the policy of induction arms of trials, there were significantly fewer caesarean sections compared with expectant management in 21 trials of 8749 women (RR 0.89, 95% CI 0.81 to 0.97).

AUTHORS' CONCLUSIONS

A policy of labour induction compared with expectant management is associated with fewer perinatal deaths and fewer caesarean sections. Some infant morbidities such as meconium aspiration syndrome were also reduced with a policy of post-term labour induction although no significant differences in the rate of NICU admission were seen.However, the absolute risk of perinatal death is small. Women should be appropriately counselled in order to make an informed choice between scheduled induction for a post-term pregnancy or monitoring without induction (or delayed induction).

Postterm pregnancy

Postterm pregnancy is a pregnancy that extends to 42 weeks of gestation or beyond. Fetal, neonatal and maternal complications associated with this condition have always been underestimated. It is not well understood why some women become postterm although in obesity, hormonal and genetic factors have been implicated. The management of postterm pregnancy constitutes a challenge to clinicians; knowing who to induce, who will respond to induction and who will require a caesarean section (CS). The current definition and management of postterm pregnancy have been challenged in several studies as the emerging evidence demonstrates that the incidence of complications associated with postterm pregnancy also increase prior to 42 weeks of gestation. For example the incidence of stillbirth increases from 39 weeks onwards with a sharp rise after 40 weeks of gestation. Induction of labour before 42 weeks of gestation has the potential to prevent these complications; however, both patients and clinicians alike are concerned about risks associated with induction of labour such as failure of induction and increases in CS rates. There is a strong body of evidence however that demonstrates that induction of labour at term and prior to 42 weeks of gestation (particularly between 40 & 42 weeks) is associated with a reduction in perinatal complications without an associated increase in CS rates. It seems therefore that a policy of induction of labour at 41 weeks in postterm women could be beneficial with potential improvement in perinatal outcome and a reduction in maternal complications.

Elective induction for pregnancies at or beyond 41 weeks of gestation and its impact on stillbirths: a systematic review with meta-analysis

Background

An important determinant of pregnancy outcome is the timely onset of labor and birth. Prolonged gestation complicates 5% to 10% of all pregnancies and confers increased risk to both the fetus and mother. The purpose of this review was to study the possible impact of induction of labour (IOL) for post-term pregnancies compared to expectant management on stillbirths.

Methods

A systematic review of the published studies including randomized controlled trials, quasi- randomized trials and observational studies was conducted. Search engines used were PubMed, the Cochrane Library, the WHO regional databases and hand search of bibliographies. A standardized data abstraction sheet was used. Recommendations have been made for input to the Lives Saved Tool (LiST) model by following standardized guidelines developed by the Child Health Epidemiology Reference Group (CHERG).

Results

A total of 25 studies were included in this review. Meta-analysis of 14 randomized controlled trials (RCTs) suggests that a policy of elective IOL for pregnancies at or beyond 41 weeks is associated with significantly fewer perinatal deaths (RR=0.31; 95% CI: 0.11-0.88) compared to expectant management, but no significant difference in the incidence of stillbirth (RR= 0.29; 95% CI: 0.06-1.38) was noted. The included trials evaluating this intervention were small, with few events in the intervention and control group. There was significant decrease in incidence of neonatal morbidity from meconium aspiration (RR = 0.43, 95% CI 0.23-0.79) and macrosomia (RR = 0.72; 95% CI: 0.54 – 0.98). Using CHERG rules, we recommended 69% reduction as a point estimate for the risk of stillbirth with IOL for prolonged gestation (> 41 weeks).

Conclusions

Induction of labour appears to be an effective way of reducing perinatal morbidity and mortality associated with post-term pregnancies. It should be offered to women with post-term pregnancies after discussing the benefits and risks of induction of labor.

Vaginal prostaglandin (PGE2 and PGF2a) for induction of labour at term

BACKGROUND

Prostaglandins have been used for induction of labour since the 1960s. Initial work focused on prostaglandin F2a as prostaglandin E2 was considered unsuitable for a number of reasons. With the development of alternative routes of administration, comparisons were made between various formulations of vaginal prostaglandins.

OBJECTIVES

To determine the effects of vaginal prostaglandins E2 and F2a for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment or other vaginal prostaglandins (except misoprostol).

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2009) and bibliographies of relevant papers.

SELECTION CRITERIA

Clinical trials comparing vaginal prostaglandins used for third trimester cervical ripening or labour induction with placebo/no treatment or other methods listed above it on a predefined list of labour induction methods.

DATA COLLECTION AND ANALYSIS

We assessed studies and extracted data independently.

MAIN RESULTS

Sixty-three (10,441 women) have been included.Vaginal prostaglandin E2 compared with placebo or no treatment reduced the likelihood of vaginal delivery not being achieved within 24 hours (18.1% versus 98.9%, risk ratio (RR) 0.19, 95% confidence interval (CI) 0.14 to 0.25, two trials, 384 women). The risk of the cervix remaining unfavourable or unchanged was reduced (21.6% versus 40.3%, RR 0.46, 95% CI 0.35 to 0.62, five trials, 467 women); and the risk of oxytocin augmentation reduced (35.1% versus 43.8%, RR 0.83, 95% CI 0.73 to 0.94, 12 trials, 1321 women) when PGE2 was compared to placebo. There was no evidence of a difference between caesarean section rates, although the risk of uterine hyperstimulation with fetal heart rate changes was increased (4.4% versus 0.49%, RR 4.14, 95% CI 1.93 to 8.90, 14 trials, 1259 women).PGE2 tablet, gel and pessary appear to be as efficacious as each other and the use of sustained release PGE2 inserts appear to be associated with a reduction in instrumental vaginal delivery rates (9.9 % versus 19.5%, RR 0.51, 95% CI 0.35 to 0.76, NNT 10 (6.7 to 24.0), five trials, 661 women) when compared to vaginal PGE2 gel or tablet.

AUTHORS' CONCLUSIONS

PGE2 increases successful vaginal delivery rates in 24 hours and cervical favourability with no increase in operative delivery rates. Sustained release vaginal PGE2 is superior to vaginal PGE2 gel with respect to some outcomes studied.Further research is needed to assess the best vehicle for delivering vaginal prostaglandins and this should, where possible, include some examination of the cost-analysis.

Guidelines for the management of pregnancy at 41+0 to 42+0 weeks

OBJECTIVE

To provide evidence-based guidelines for the management of pregnancy at 41+0 to 42+0 weeks.

OUTCOMES

Reduction of perinatal mortality associated with Caesarean section at 41+0 to 42+0 weeks of pregnancy.

EVIDENCE

The Medline database, the Cochrane Library, and the American College of Obstetricians and Gynecologists and the Royal College of Obstetricians and Gynecologists, were searched for English language articles published between 1966 and March 2007, using the following key words: prolonged pregnancy, post-term pregnancy, and postdates pregnancy. The quality of evidence was evaluated and recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care. Recommendations 1. First trimester ultrasound should be offered, ideally between 11 and 14 weeks, to all women, as it is a more accurate assessment of gestational age than last menstrual period with fewer pregnancies prolonged past 41+0 weeks. (I-A) 2. If there is a difference of greater than 5 days between gestational age dated using the last menstrual period and first trimester ultrasound, the estimated date of delivery should be adjusted as per the first trimester ultrasound. (I-A) 3. If there is a difference of greater than 10 days between gestational age dated using the last menstrual period and second trimester ultrasound, the estimated date of delivery should be adjusted as per the second trimester ultrasound. (I-A) 4. When there has been both a first and second trimester ultrasound, gestational age should be determined by the earliest ultrasound. (I-A) 5. Women should be offered the option of membrane sweeping commencing at 38 to 41 weeks, following a discussion of risks and benefits. (I-A) 6. Women should be offered induction at 41+0 to 42+0 weeks, as the present evidence reveals a decrease in perinatal mortality without increased risk of Caesarean section. (I-A) 7. Antenatal testing used in the monitoring of the 41- to 42-week pregnancy should include at least a non-stress test and an assessment of amniotic fluid volume. (I-A) 8. Each obstetrical department should establish guidelines dependent on local resources for scheduling of labour induction. (I-A).

Postterm pregnancy: should all women have labour induced? A review of the literature

All pregnancies are at some risk of adverse fetal and neonatal outcome. The risk increases, however, if the pregnancy ends too soon (preterm), or if it ends too late (postterm).

WITHDRAWN: Interventions for preventing or improving the outcome of delivery at or beyond term

BACKGROUND

Perinatal mortality and morbidity is increased in pregnancies of more than 42 weeks that are otherwise low risk.

OBJECTIVES

The objective of this review was to assess the effects of interventions aimed at either reducing the incidence or improving the outcome of post-term pregnancy.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register was searched.

SELECTION CRITERIA

Randomised and quasi-randomised trials of interventions involving the intention to induce labour at a specified gestational age.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed by one reviewer. Study authors were contacted for additional information.

MAIN RESULTS

Twenty-six trials of variable quality were included. There were four trials of routine early pregnancy ultrasound, two of nipple stimulation, nineteen of routine versus selective induction of labour and one of antenatal fetal monitoring. Routine early pregnancy ultrasound reduced the incidence of post-term pregnancy (odds ratio 0.68, 95% confidence interval 0.57 to 0.82). Breast and nipple stimulation at term did not affect the incidence of post-term pregnancy (odds ratio 0.52, 95% confidence interval 0.28 to 0.96). Routine induction of labour reduced perinatal mortality (odds ratio 0.20, 95% confidence interval 0.06 to 0.70). This benefit is due to the effect of induction of labour after 41 weeks. Routine induction of labour had no effect on caesarean section.

AUTHORS' CONCLUSIONS

Routine early pregnancy ultrasound examination and subsequent adjustment of delivery date appear to reduce the incidence of post-term pregnancy. Routine induction of labour after 41 weeks gestation appears to reduce perinatal mortality. There is not enough evidence to evaluate the effects of breast and nipple stimulation, or tests of fetal wellbeing.(This abstract has been prepared centrally.).

Induction of labour for improving birth outcomes for women at or beyond term

BACKGROUND

As a pregnancy continues beyond term the risks of babies dying inside the womb or in the immediate newborn period increase. Whether a policy of labour induction at a predetermined gestational age can reduce this increased risk is the subject of this review.

OBJECTIVES

To evaluate the benefits and harms of a policy of labour induction at term or post-term compared to awaiting spontaneous labour or later induction of labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (June 2006).

SELECTION CRITERIA

Randomized controlled trials conducted in women at or beyond term. The eligible trials were those comparing a policy of labour induction to a policy of awaiting spontaneous onset of labour. Trials comparing cervical ripening methods, membrane stripping/sweeping or nipple stimulation without any commitment to delivery within a certain time were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated potentially eligible trials and extracted data. Outcomes are analysed in two main categories: gestational age and cervix status.

MAIN RESULTS

We included 19 trials reporting on 7984 women. A policy of labour induction at 41 completed weeks or beyond was associated with fewer (all-cause) perinatal deaths (1/2986 versus 9/2953; relative risk (RR) 0.30; 95% confidence interval (CI) 0.09 to 0.99). The risk difference is 0.00 (95% CI 0.01 to 0.00). If deaths due to congenital abnormality are excluded, no deaths remain in the labour induction group and seven deaths remain in the no-induction group. There was no evidence of a statistically significant difference in the risk of caesarean section (RR 0.92; 95% CI 0.76 to 1.12; RR 0.97; 95% CI 0.72 to 1.31) for women induced at 41 and 42 completed weeks respectively. Women induced at 37 to 40 completed weeks were more likely to have a caesarean section with expectant management than those in the labour induction group (RR 0.58; 95% CI 0.34 to 0.99). There were fewer babies with meconium aspiration syndrome (41+: RR 0.29; 95% CI 0.12 to 0.68, four trials, 1325 women; 42+: RR 0.66; 95% CI 0.24 to 1.81, two trials, 388 women).

AUTHORS' CONCLUSIONS

A policy of labour induction after 41 completed weeks or later compared to awaiting spontaneous labour either indefinitely or at least one week is associated with fewer perinatal deaths. However, the absolute risk is extremely small. Women should be appropriately counselled on both the relative and absolute risks.

The rhetoric of “natural” in natural childbirth: childbearing women's perspectives on prolonged pregnancy and induction of labour

It is widely known that the notion of prolonged pregnancy, defined medically as 41+ or 42+ weeks gestation, has been hotly debated within the medical and midwifery communities for many decades. Within this debate, pregnant women's voices have rarely been heard. Presented here are the results of a qualitative study of self-care in pregnancy, birth and lactation with a non-random sample of women in British Columbia, Canada. A panel of 27 women was interviewed in the third trimester of pregnancy, and 23 of the same participants were re-interviewed post-partum (50 interviews in total). Interviews were tape-recorded, transcribed, and analyzed thematically. Many of the women said they favoured a natural birth and were opposed to labour induction at the time of the first interview. Yet all but one of the ten women who went beyond 40 weeks gestation used self-help measures to stimulate labour. These women did not perceive prolonged pregnancy as a medical problem per se. Rather they saw it as an inconvenience, a worry to their friends, families and maternity care providers, and a prolongation of physical discomfort. The findings are interpreted by examining the literature on the medicalization/healthicization of childbirth.

Prolonged pregnancy: the management dilemma

In a prospective randomized study, pregnancies with unfavorable cervix and well established gestational age of at least 42 weeks were selected for management by either antepartum fetal testing or prostaglandin gel induction of labor. Of the 108 pregnancies studied, 57 (53%) had labor induced and 51 (47%) continued without intervention. Comparison of the two groups showed no difference in meconium staining, fetal distress, length of first stage of labor, the need for intervention, or the mode of delivery. In terms of Apgar score the neonatal outcome was not significantly different but a greater proportion of the babies (7.8% versus 1.8%) in the noninduced group required intubation. Our data show that there is no particular advantage in letting the pregnancy go beyond 42 completed weeks of gestation especially if prostaglandin is available for induction of labor.

Induction of labour with a favourable cervix and/or pre-labour rupture of membranes

Premature rupture of membranes (PROM) occurs in 8% of term deliveries. In this situation labour induction with prostaglandins, compared with expectant management, results in a reduced risk of chorioamnionitis, neonatal antibiotic therapy, neonatal intensive care (NICU) admission, and increased maternal satisfaction. The use of prostaglandin is associated with an increased rate of diarrhoea and use of analgesia/anaesthesia. Compared with oxytocin, prostaglandin induction results in a lower rate of epidural use and internal fetal heart rate monitoring but a greater risk of chorioamnionitis, nausea, vomiting, more vaginal examinations, neonatal antibiotic therapy, NICU admission and neonatal infection. Women should be informed of the risks and benefits of each method of induction.Misoprostol is gaining increasing interest as an alternative induction agent. It appears to be an effective method of labour induction with term PROM. Further research is needed to identify the preferred dosage, route and interval of administration, and to assess uncommon maternal and neonatal outcomes. There has been limited research on the use of prostaglandins, including misoprostol, for induction of labour with a favourable cervix and intact membranes. Compared with intravenous oxytocin (with and without amniotomy), labour induction using vaginal prostaglandins in women with a favourable cervix (with and without PROM) results in a higher rate of vaginal delivery within 24 hours and increased maternal satisfaction. In women with a favourable cervix, artificial rupture of membranes followed by oral misoprostol has similar time to vaginal delivery compared with artificial rupture of membranes followed by oxytocin. Further research with prostaglandins, including misoprostol, is needed to evaluate other maternal and neonatal outcomes in women being induced with a favourable cervix. No form of prostaglandin induction in women with PROM or favourable cervix has proven clearly superior to oxytocin infusion.

Vaginal prostaglandin (PGE2 and PGF2a) for induction of labour at term

BACKGROUND

Prostaglandins have been used for induction of labour since the 1960s. Initial work focused on prostaglandin F2a as prostaglandin E2 was considered unsuitable for a number of reasons. With the development of alternative routes of administration, comparisons were made between various formulations of vaginal prostaglandins. This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology.

OBJECTIVES

To determine the effects of vaginal prostaglandins E2 and F2a for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment or other vaginal prostaglandins (except misoprostol).

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register (May 2003) and bibliographies of relevant papers.

SELECTION CRITERIA

Clinical trials comparing vaginal prostaglandins used for third trimester cervical ripening or labour induction with placebo/no treatment or other methods listed above it on a predefined list of labour induction methods.

DATA COLLECTION AND ANALYSIS

A strategy was developed to deal with the large volume and complexity of trial data relating to labour induction. This involved a two-stage method of data extraction.

MAIN RESULTS

In total, 101 studies were considered: 43 excluded and 57 (10,039 women) included. One study is awaiting assessment. Vaginal prostaglandin E2 compared with placebo or no treatment reduced the likelihood of vaginal delivery not being achieved within 24 hours (18% versus 99%, relative risk (RR) 0.19, 95% confidence interval (CI) 0.14 to 0.25, 2 trials, 384 women), there was no evidence of a difference between caesarean section rates although the risk of uterine hyperstimulation with fetal heart rate changes was increased (4.6% versus 0.51%, RR 4.14, 95% CI 1.93 to 8.90, 13 trials, 1203 women). Comparison of vaginal prostaglandin F2a with placebo showed similar caesarean section rates but the cervical score was more likely to be improved (15% versus 60%, RR 0.25, 95% CI 0.13 to 0.49, 5 trials, 467 women), and the risk of oxytocin augmentation reduced (53.9% versus 89.1%, RR 0.60, 95% CI 0.43 to 0.84, 11 trials, 1265 women) with the use of vaginal PGF2a. There were insufficient data to make meaningful conclusions for the comparison of vaginal PGE2 and PGF2a.PGE2 tablet, gel and pessary appear to be as efficacious as each other. Lower dose regimens, as defined in the review, appear as efficacious as higher dose regimens.

REVIEWER'S CONCLUSIONS

The primary aim of this review was to examine the efficacy of vaginal prostaglandin E2 and F2a. This is reflected by an increase in successful vaginal delivery rates in 24 hours, no increase in operative delivery rates and significant improvements in cervical favourability within 24 to 48 hours. Further research is needed to quantify the cost-analysis of induction of labour with vaginal prostaglandins, with special attention to different methods of administration.

Exploring the risks associated with induction of labour: a retrospective study using the NIMATS database. Northern Ireland Maternity System

Induction of labour is a valuable obstetric procedure, providing obstetricians with the means to intervene should the health of the fetus be in jeopardy. Currently the most common reason for induction of labour is prolonged pregnancy, as obstetricians and midwives are concerned about the risks of postmaturity such as stillbirth, intrapartum asphyxia and birth trauma which are often associated with prolonged pregnancy (Lagrew & Freeman 1986). A retrospective comparative study was carried out in a large maternity unit to identify whether or not there was clinical evidence to support a policy of elective induction for post-term pregnancy. Three years' data were extracted from the Northern Ireland Maternity System (NIMATS) by writing new queries to the system. These data on 3262 women who delivered during 1994-96 were analysed to compare the outcomes for women who were induced with women who delivered spontaneously. Although the findings from the study in many instances failed to demonstrate statistical significance between the groups they did however, have important clinical significance. For example, those women who were induced had a 5% higher rate of caesarean section, 17% higher rate of epidural analgesia and on average a greater estimated blood loss. Statistical significance was evident when the apgar scores of the infants were compared; those induced had lower Apgars at 1 minute (7. 78 in the induced group compared to 7.9 in the spontaneous group [P < 0.01]) and at 5 min (8.99 in the induced group compared to 9.05 in the spontaneous group [P < 0.02]).

Fetal distress

The term 'fetal distress' should be replaced by 'suspected fetal compromise' because the diagnosis of 'fetal distress' is often unproven. Cardiotocography remains the cornerstone of making the diagnosis, but as a test it is renowned for its high sensitivity and low specificity. It has reduced intrapartum fetal mortality but not long-term neonatal morbidity or the incidence of cerebral palsy. There is no doubt that when obvious signs of fetal compromise, such as late decelerations in the presence of intrauterine growth retardation and oligohydramnios, are present, the diagnosis of fetal compromise is relatively simple. Often, however, the subtle signs of fetal compromise are missed; these are a change in the grade of meconium in the amniotic fluid, a rising base-line fetal heart rate, the absence of accelerations, the presence of 'atypical' variable decelerations or a combination of the above. To date, there is no test available to replace the cardiotocograph, although fetal pulse oximetry is the most promising adjunctive test. Above all, no test result obtained in isolation must detract from the whole clinical picture.

Interventions for preventing or improving the outcome of delivery at or beyond term

BACKGROUND

Perinatal mortality and morbidity is increased in pregnancies of more than 42 weeks that are otherwise low risk.

OBJECTIVES

The objective of this review was to assess the effects of interventions aimed at either reducing the incidence or improving the outcome of post-term pregnancy.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register was searched.

SELECTION CRITERIA

Randomised and quasi-randomised trials of interventions involving the intention to induce labour at a specified gestational age.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed by one reviewer. Study authors were contacted for additional information.

MAIN RESULTS

Twenty-six trials of variable quality were included. There were four trials of routine early pregnancy ultrasound, two of nipple stimulation, nineteen of routine versus selective induction of labour and one of antenatal fetal monitoring. Routine early pregnancy ultrasound reduced the incidence of post-term pregnancy (odds ratio 0.68, 95% confidence interval 0.57 to 0.82). Breast and nipple stimulation at term did not affect the incidence of post-term pregnancy (odds ratio 0.52, 95% confidence interval 0.28 to 0.96). Routine induction of labour reduced perinatal mortality (odds ratio 0.20, 95% confidence interval 0.06 to 0.70). This benefit is due to the effect of induction of labour after 41 weeks. Routine induction of labour had no effect on caesarean section.

REVIEWER'S CONCLUSIONS

Routine early pregnancy ultrasound examination and subsequent adjustment of delivery date appear to reduce the incidence of post-term pregnancy. Routine induction of labour after 41 weeks gestation appears to reduce perinatal mortality. There is not enough evidence to evaluate the effects of breast and nipple stimulation, or tests of fetal wellbeing.

Intracellular calcium stores and agonist-induced contractions in isolated human myometrium

OBJECTIVE

We hypothesized that the release of calcium from intracellular stores contributes to the contractions produced by the agonists oxytocin, carbachol, and prostaglandin F(2 )(alpha ) in human myometrium.

STUDY DESIGN

Strips of myometrium were obtained at cesarean section and hysterectomy. The strips were loaded with the calcium-sensitive dye Indo-1 to enable simultaneous measurement of tension and intracellular calcium levels. Agonist-induced responses in the presence and absence of extracellular calcium were studied.

RESULTS

Strips of myometrium were obtained from 48 women not in labor undergoing cesarean section and 6 women not pregnant undergoing hysterectomy. An increase in intracellular calcium level after agonist stimulation invariably preceded an increase in tension. Intracellular calcium level returned to baseline before myometrial relaxation. Oxytocin, carbachol, and prostaglandin F(2)(alpha) all gave both force and intracellular calcium responses in the absence of extracellular calcium, although both these responses were only 26% to 40% of the maximal response when extracellular calcium was present.

CONCLUSIONS

Release of calcium from internal stores induced by oxytocin, carbachol, and prostaglandin F(2)(alpha) may contribute to agonist-induced myometrial force production.

Effect of labour induction on rates of stillbirth and cesarean section in post-term pregnancies

BACKGROUND

Meta-analyses of randomized controlled trials suggest that elective induction of labour at 41 weeks' gestation, compared with expectant management with selective labour induction, is associated with fewer perinatal deaths and no increase in the cesarean section rate. The authors studied the changes over time in the rates of labour induction in post-term pregnancies in Canada and examined the effects on the rates of stillbirth and cesarean section.

METHODS

Changes in the proportion of total births at 41 weeks' and at 42 or more weeks' gestation, and in the rate of stillbirths at 41 or more weeks' (versus 40 weeks') gestation in Canada between 1980 and 1995 were determined using data from Statistics Canada. Changes in the rates of labour induction and cesarean section were determined using data from hospital and provincial sources.

RESULTS

There was a marked increase in the proportion of births at 41 weeks' gestation (from 11.9% in 1980 to 16.3% in 1995) and a marked decrease in the proportion at 42 or more weeks (from 7.1% in 1980 to 2.9% in 1995). The rate of stillbirths among deliveries at 41 or more weeks' gestation decreased significantly, from 2.8 per 1000 total births in 1980 to 0.9 per 1000 total births in 1995 (p < 0.001). The stillbirth rate also decreased significantly among births at 40 weeks' gestation, from 1.8 per 1000 total births in 1980 to 1.1 per 1000 total births in 1995 (p < 0.001). The magnitude of the decrease in the stillbirth rate at 41 or more weeks' gestation was greater than that at 40 weeks' gestation (p < 0.001). All hospital and provincial sources of data indicated that the rate of labour induction increased significantly between 1980 and 1995 among women delivering at 41 or more weeks' gestation. The associated changes in rates of cesarean section were variable.

INTERPRETATION

Between 1980 and 1995 clinical practice for the management of post-term pregnancy changed in Canada. The increased rate of labour induction at 41 or more weeks' gestation may have contributed to the decreased stillbirth rate but it had no convincing influence either way on the cesarean section rate.

Induction of labour for post term pregnancy: an observational study

The aim of the study was to compare the 2 management protocols for postterm pregnancy; elective induction of labour at 42 weeks' gestation and continuing the pregnancy with fetal monitoring while awaiting spontaneous labour. A retrospective observational study compared a cohort of 360 pregnancies where labour was induced with 486 controls. All pregnancies were postterm (>294 days) by an early ultrasound scan. Induction of labour was achieved with either prostaglandin vaginal pessaries or gel or forewater rupture and Syntocinon infusion. The control group consisted of women with postterm pregnancies who were not induced routinely and who usually had twice weekly fetal assessment with cardiotocography and/or ultrasound. Women who had their labour induced differed from those who awaited spontaneous labour. Nulliparas (OR 1.54; 95% CI 1.24-1.83) and married women (OR 1.76; 95% CI 1.45-2.06) were more likely to have their labour induced. There was no association between the type of caregiver and induction of labour. Induction of labour was associated with a reduction in the incidence of normal vaginal delivery (OR 0.63, 95% CI 0.43-0.92) and an increased incidence of operative vaginal delivery (OR 1.46; 95% CI 1.34-2.01). There was no difference in the overall rate of Caesarean section. There was no difference in fetal or neonatal outcomes. Parity had a major influence on delivery outcomes from a policy of induction of labour. Nulliparas in the induced group had worse outcomes with only 43% achieving a normal vaginal delivery (OR 0.78, 95% CI 0.65-0.95). In contrast for multiparas, the induced group had better outcomes with less Caesarean sections (OR 0.88, 95% CI 0.81-0.96). This retrospective observational study of current clinical practice shows that induction of labour for postterm pregnancy appears to be favoured by nulliparous married women. It suggests that induction of labour may improve delivery outcomes for multigravas but has an adverse effect for nulliparas.

Computerised evaluation of fetal heart rate in post-term fetuses: long term variation

Computerised fetal heart rate records were obtained between 1987 and 1993 using the Sonicaid System 8000 for a cross-sectional study of postdates fetal heart rate variation; 567 singleton pregnancies at 41 and 43 weeks provided 1502 records. In all cases gestational age had been verified by ultrasound examination in early pregnancy. The mean minute range of the long term pulse interval variation, which is known to be correlated with fetal oxygenation was found to decrease progressively from an average value of 48.5 ms at 41 weeks to 46.4 ms and 42.4 ms at 42 and 43 or more weeks, respectively. When conservative management of postdate pregnancies is chosen, accurate measurements are needed to follow the evolution of fetal condition. Reference values for calculated pulse interval variation at later gestational ages are now provided.

Postterm pregnancy: putting the merits of a policy of induction of labor into perspective

BACKGROUND

Several randomized, controlled trials compared the policies of induction of labor and expectant management for women who reach 41 weeks' gestation, and although they suggest a better outcome for mothers and infants with such a policy in place, controversy continues as to which is the better form of care. The Canadian Multicenter Postterm Pregnancy Trial (CMPPT) enrolled 3407 women, of whom 1701 were randomized to a policy of induction of labor (induced group) and 1706 were randomized to a policy of expectant management (expectant group). Secondary analyses of data from the CMPPT were undertaken to explore a number of controversial issues.

METHODS

We used data from the CMPPT to explore further the timing of delivery for women enrolled between 41 0/7 and 41 6/7 weeks' gestation, the potential impact of more liberal use of prostaglandins on cesarean section rates, and the relative merits of induced versus spontaneous labor in the two groups.

RESULTS

Most women in the CMPPT (89%) were enrolled at 41 0/7 to 41 6/7 weeks' gestation, of whom 86.2 percent in the induced group and 63.6 percent in the expectant group gave birth before 42 weeks' gestation. Assuming that administration of prostaglandins would reduce the likelihood of cesarean section by 12 to 15 percent, cesarean section rates were reduced in the induction group from 21.2 percent to 20.8 to 20.9 percent, and in the expectant group from 24.5 percent 23.3 to 24.2 percent. If labor was induced as part of a policy of expectant management, the cesarean section rate was much higher (33.5%) than if labor was either spontaneous or induced as part of a policy of induction (18.5%, 22.4%).

CONCLUSIONS

Women should be informed of the benefits and risks associated with the policies of induction of labor and expectant management, and their preferences regarding these policies should be respected.

Does labor start too late?

To determine the optimal time of delivery, in terms of lowest risk of peripartum complications, the relative incidences of the parameters. Abnormal cardiotocogram (CTG), operative vaginal delivery, Apgar < 7 at 1 and 5 min, artery cord blood pH < 7.20, blood loss > 500 ml, epidural anesthesia, and Cesarean section, were retrospectively analysed with regard to mode of labor onset (spontaneous, induced) and gestational age in all deliveries between gestational weeks (GW) 35 + 0/7 and 42 + 6/7 from 1986 through 1993 at Zurich University Hospital (n = 11,834) and additionally with regard to birth weight in the same population from 1987 through 1993 (n = 10,346). The distribution of most parameters was parabolic with nadirs at GW 37-38; the incidence of low Apgar scores and Cesarean sections, however, was lowest nearer term (GW 39-40). Mode of labor onset had little effect (< or = 1 week) on the time of lowest incidence. The birth weight associated with the fewest complications was 3000 g, with the optimal time of delivery being GW 37-38, assuming a birth weight normal for gestational age.

Post-term pregnancies with normal cardiotocographs and amniotic fluid columns: the role of Doppler evaluation in predicting perinatal outcome

OBJECTIVE

To study the role of Doppler ultrasound examination in predicting an abnormal perinatal outcome, among post-term pregnancies uncomplicated by an abnormal non-stress test (NST) or reduced amount of amniotic fluid.

DESIGN

A prospective study.

SETTING

High-risk pregnancy unit, Hadassah Mt. Scopus University Hospital, Jerusalem.

SUBJECTS

Seventy-eight women with confirmed gestational age of > 287 days, who had normal initial evaluation and unfavourable cervical examination.

INTERVENTIONS

Doppler flow velocity waveforms were recorded from the umbilical and middle cerebral arteries, and from the descending thoracic aorta.

MAIN OUTCOME MEASURES

Correlation between Doppler measurements and data regarding delivery.

RESULTS

Women who developed signs of fetal distress during labour, or who required intervention because of fetal distress, had elevated umbilical artery systolic/diastolic ratio, decreased middle cerebral artery pulsatility index, and decreased time average aortic blood flow velocity. Umbilical artery Doppler measurements could significantly predict the need for intervention due to fetal distress.

CONCLUSIONS

Doppler examination of uncomplicated post-term pregnancies may identify patients with normal results as having a low risk of developing fetal distress during labour. Patients with abnormal Doppler results are prone to need intervention following fetal distress in labour.

Sweeping the membranes: a valid procedure in stimulating the onset of labour?

OBJECTIVE

To determine whether sweeping the membranes in pregnancies of longer than 40 weeks gestation results in an accelerated onset of labour and a reduction in the incidence of induction of labour.

DESIGN

A prospective randomised controlled study.

SETTING

The antenatal clinic of a district general hospital.

SUBJECTS

One hundred and ninety-five antenatal women with pregnancies proceeding beyond 40 weeks gestation.

INTERVENTIONS

A Bishop score assessment of the cervix alone or combined with a membrane sweep, on a randomised basis.

OUTCOME MEASURES

Subsequent duration of pregnancy to the onset of spontaneous labour. The incidence of induction of labour for post-maturity.

RESULTS

Sweeping the membranes significantly reduces the subsequent duration of pregnancy, from an average of five days to two days following the procedure. The proportion of inductions of labour was 8.1% in the swept group and 18.8% in the control group. No harmful side effects to the procedure were noted.

CONCLUSIONS

Sweeping the membranes is a safe and useful procedure which results in a reduced incidence of post-mature pregnancies, and a subsequent reduction in the labour induction rate.

Labour induction policy in hospitals of different levels of specialisation

OBJECTIVE

To examine indications for the induction of labour and variations in the current policy of induction at different levels of obstetric specialisation and to compare the outcome of induced and spontaneous labour.

DESIGN

A prospective 1 year birth cohort.

SETTING

Maternity hospitals in the two northernmost administrative provinces of Finland, including one university hospital and three central hospitals, three local hospitals and five health centres.

SUBJECTS

Eight thousand six hundred and six singleton pregnancies, including 1679 with induced labour.

MAIN OUTCOME MEASURE

Data collection on age, parity, social factors and education at antenatal clinic. Data on labour collected from the hospital records after delivery.

RESULTS

Labour was induced significantly more often at units of the lowest level of specialisation, the health centres (29.4%) than at the local hospitals (23.6%, P < 0.003) or in the most specialised central hospitals (17.7%, P < 0.0001). Cases of induced labour accumulated on working days. Indicative reasons, such as maternal or fetal conditions, comprised 45.0% of the indications for induction, the most common causes being elective reasons, e.g. timing of labour (51.3%). The risk of elective induction was 2.6 times greater at the primary care level than at the central hospitals (95% confidence limit, CL 2.0-3.2). The corresponding risk ratio for local hospitals was 1.8 (CL 1.5-2.1). The risk of caesarean section was 1.5 times greater in the elective induction group than in the spontaneous group (CL 1.1-1.9) and 2.9 times greater in the indicative induction group. The most common indication for caesarean section was dysfunctional, arrested labour, causes such as fetal asphyxia or antenatal haemorrhage were not seen in excess.

CONCLUSION

The practice of induction of labour are not consistent in different hospitals. The opinions of individual practitioners and staff routines influence the induction policy nearly as much as do medical reasons. Despite the safety of induction, a liberal induction policy leads to an increase in operative deliveries creating potential risks for the mother and child and greater expense.

Is routine induction of labour at term ever justified?

Balancing the risks of prolonged gestation against those of induced labour is difficult. Risks to the fetus increase slightly after 42 weeks' gestation but women having labour induced are more likely to have instrumental deliveries or babies with low Apgar scores. Since many women are now expressing a preference for minimal interference in childbirth the most acceptable management of post-term pregnancy seems to be increased fetal surveillance. Each case needs to be considered individually and it is important that the woman is involved in the decision to induce.

Active management of prolonged pregnancy

OBJECTIVES

We assessed perinatal morbidity and mortality of prolonged pregnancies (> or = 294 days) compared with those of term gestations. We also evaluated the impact of induction of labor compared with spontaneous onset of labor.

STUDY DESIGN

This observational study included consecutive cases treated at Chicago Lying-In Hospital from July 1980 to December 1984. Complications, presence of meconium, indications for cesarean section, mode of delivery, perinatal morbidity (and mortality), meconium aspiration, and duration of labor were compared with those in the total hospital population, in infants weighing > or = 2500 gm, and within prolonged gestation groups; spontaneous onset and induced ("active management") labors were also compared. The chi 2 analysis was used.

RESULTS

Of 12,930 deliveries there were 707 prolonged gestations (5.5%) and 10,698 with infants > or = 2500 gm. Among the prolonged gestations 67% were in multiparous women and 33% in primiparous women. Labor started spontaneously in 62%, and 38% underwent induction; the overall cesarean section rate was 17% with similar indications in both spontaneous onset and induction groups. Meconium was present in 34%; it was present in 23% of inductions, which is fewer (p < 0.01) than among those with spontaneous onset of labor (40%). Also there were fewer depressed neonates at 5 minutes (p = 0.03) among inductions. Meconium aspiration was seen in 24, with nine deaths. The perinatal mortality was 14 per 1000 (corrected 12.7/1000), significantly more than in the general population. Among those with spontaneous onset of labor it was 20.5 per 1000; there were no deaths among inductions. Postpartum maternal morbidity was 16% among cesarean sections and 4% among vaginal deliveries.

CONCLUSIONS

Prolonged gestation has a high perinatal morbidity and mortality rate. All perinatal deaths were observed among patients whose labor started spontaneously. "Active management" (induction at 42 weeks) did increase the primary cesarean section rate compared with that of the general obstetric population; it did not do so among prolonged gestations and prevented perinatal deaths in this group. From this experience an active approach seems justified.