Induction of labour versus expectant management at term by subgroups of maternal age: an individual patient data meta-analysis

Comparison of Maternal Labor-Related Complications and Neonatal Outcomes Following Elective Induction of Labor at 39 Weeks of Gestation vs Expectant Management: A Systematic Review and Meta-analysis

Importance

Elective induction of labor at 39 weeks of gestation is common. Thus, there is a need to assess maternal labor-related complications and neonatal outcomes associated with elective induction of labor.

Objective

To examine maternal labor-related complications and neonatal outcomes following elective induction of labor at 39 weeks compared with expectant management.

Data Sources

A systematic review of the literature was conducted using the MEDLINE (Ovid), Embase (Ovid), Cochrane Central Library, World Health Organization, and ClinicalTrials.gov databases and registries to search for articles published between database inception and December 8, 2022.

Study Selection

This systematic review and meta-analysis included randomized clinical trials, cohort studies, and cross-sectional studies reporting perinatal outcomes following induction of labor at 39 weeks vs expectant management.

Data Extraction and Synthesis

Two reviewers independently assessed study eligibility, extracted data, and assessed studies for bias. Pooled odds ratios (ORs) and 95% CIs were calculated using a random-effects model. This study is reported per the Preferred Reporting Items for Systematic Reviews and Meta-analyses 2020 guideline, and the protocol was prospectively registered with PROSPERO.

Main Outcomes and Measures

Maternal outcomes of interest included emergency cesarean section, perineal injury, postpartum hemorrhage, and operative vaginal birth. Neonatal outcomes of interest included admission to the neonatal intensive care unit, low 5-minute Apgar score (<7) after birth, macrosomia, and shoulder dystocia.

Results

Of the 5827 records identified in the search, 14 studies were eligible for inclusion in this review. These studies reported outcomes for 1 625 899 women birthing a singleton pregnancy. Induction of labor at 39 weeks of gestation was associated with a 37% reduced likelihood of third- or fourth-degree perineal injury (OR, 0.63 [95% CI, 0.49-0.81]), in addition to reductions in operative vaginal birth (OR, 0.87 [95% CI, 0.79-0.97]), macrosomia (OR, 0.66 [95% CI, 0.48-0.91]), and low 5-minute Apgar score (OR, 0.62 [95% CI, 0.40-0.96]). Results were similar when confined to multiparous women only, with the addition of a substantial reduction in the likelihood of emergency cesarean section (OR, 0.61 [95% CI, 0.38-0.98]) and no difference in operative vaginal birth (OR, 1.01 [95% CI, 0.84-1.21]). However, among nulliparous women only, induction of labor was associated with an increased likelihood of shoulder dystocia (OR, 1.22 [95% CI, 1.02-1.46]) compared with expectant management.

Conclusions and Relevance

In this study, induction of labor at 39 weeks was associated with improved maternal labor-related and neonatal outcomes. However, among nulliparous women, induction of labor was associated with shoulder dystocia. These results suggest that elective induction of labor at 39 weeks may be safe and beneficial for some women; however, potential risks should be discussed with nulliparous women.

Synthetic osmotic dilators (Dilapan-S) or dinoprostone vaginal inserts (Propess) for inpatient induction of labour: A UK cost-consequence model

OBJECTIVE

To estimate the costs of synthetic osmotic dilators (Dilapan-S) compared to dinoprostone vaginal inserts (Propess) for inpatient induction of labour (IOL).

STUDY DESIGN

A population-level, Markov model-based cost-consequence analysis was developed to compare the impact of using Dilapan-S versus Propess. The time horizon was modelled from admission to birth. The target population was women requiring inpatient IOL from 37 weeks with an unfavourable cervix in the UK. Mean population characteristics reflected those of the SOLVE (NCT03001661) trial. No patient data were included in this analysis. The care pathways and staff workload were modelled using data from the SOLVE trial and clinical experience. Cost and clinical inputs were sourced from the SOLVE trial and peer-reviewed literature. Costs were inflated to 2020 British pounds (GBP, £). Outcomes were reported as an average per woman for total costs and required staff time (minutes) from admission for IOL until birth. The model robustness was assessed using a probabilistic, multivariate sensitivity analysis of 2,000 simulations with results presented as the median (interquartile range, IQR).

RESULTS

Dilapan-S was cost neutral compared to Propess. Midwife and obstetrician times were decreased by 146 min (-11%) and 11 min (-54%), respectively. Sensitivity analysis showed that in 78% of simulations, use of Dilapan-S reduced midwife time with a median of -160 min (IQR -277 to -24 min). Costs were reduced in 54% of simulations (median -£33, IQR -£319 to £282).

CONCLUSIONS

The model indicates that adoption of Dilapan-S is likely to be cost-neutral and reduce staff workload in comparison to Propess. Results require support from real-world data and further exploration of Dilapan-S is to be encouraged.

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.

RISK ASSESSMENT IN PREGNANCY AMONG WOMEN AGED OVER FORTY

The objective of this study was to assess the relationship between women's age and risk of pregnancy-related complications. The study was a retrospective cohort analysis of the pregnancy-related complications and outcomes between two age groups of parturient women. Categorical data were expressed as absolute and relative frequencies. Statistical analysis was performed using χ2-test. The incidence of gestational diabetes was higher in the 40-47 age group as compared with the 20-24 age group. The rates of hypertension, preeclampsia, intrahepatic cholestasis of pregnancy and hypothyroidism did not differ between the two groups. The rates of labor induction, oxytocin use, vaginal delivery, and need for episiotomy were higher in younger age group. Dystocia and breech presentation as indications for cesarean section were more common among younger women. According to study results, the risk of gestational diabetes and rates of cesarean delivery increased with advanced maternal age.

Clinical Outcomes in High-Risk Pregnancies Due to Advanced Maternal Age

Although the influence of advanced maternal age (AMA) and delayed childbearing on adverse maternal and perinatal outcomes has been studied extensively, no universal consensus on the definition of AMA exists. This terminology currently refers to the later years of a woman's reproductive life span and generally applies to women age ≥35 years. AMA increases the risk of pregnancy complications, including ectopic pregnancy, spontaneous abortion, fetal chromosomal abnormalities, congenital anomalies, placenta previa and abruption, gestational diabetes, preeclampsia, and cesarean delivery. Such complications could be the cause of preterm birth and increase the risk of perinatal mortality. For women who have a chronic illness, pregnancy may lead to additional risk that demands increased monitoring or surveillance. The management of pregnant women of AMA requires understanding the relationship between age and preexisting comorbidities. The outcomes from pregnancy in AMA may have a negative impact on women's health as they age because of both the changes from the pregnancy itself and the increased risk of pregnancy-related complications. Postpartum depression affects women of AMA at higher rates. Links between preeclampsia and the risk of future development of cardiovascular disease require follow-up surveillance. The association between hypertensive pregnancy disorders and cognitive and brain functions needs further investigation of sex-specific risk factors across the life span. Educating providers and women of AMA is crucial to facilitate clinical decision making and such education should consider cultural influences, risk perception, and women's health literacy, as well as providers' biases and system issues.

Does induction of labor at term increase the risk of cesarean section in advanced maternal age? A systematic review and meta-analysis

BACKGROUND

Women of advanced maternal age, defined as ≥ 35 years at delivery, are at increased risk of multiple complications during pregnancy, with perinatal death being one of the most feared. For instance, the risk of stillbirth at term in this subgroup of women is higher than in younger women, and particularly high beyond 39 weeks of gestation. Induction of labor at 39-40 weeks might help prevent some cases of perinatal death, however, the fact that induction of labor has been historically associated with an increased risk of cesarean delivery and the knowledge that advanced maternal age is an independent risk factor for cesarean delivery are some of the major reasons why clinicians are reluctant to offer elective induction of labor in this particular group.

OBJECTIVE

The aim of the study was to assess if induction of labor in advanced maternal age was associated with increased rates of cesarean delivery when compared to expectant management.

MATERIAL AND METHODS

We performed an electronic search limited to published articles available between January 2000 and March 2020. Randomized clinical trials and retrospective studies with large cohorts comparing induction of labor with expectant management in singleton pregnancies at term, of women aged ≥ 35 years were included. The primary outcome was the rate of cesarean delivery in induction of labor versus expectant management, and secondary outcomes were the occurrence of assisted vaginal delivery and postpartum hemorrhage.

RESULTS

Eight studies, including 81151 pregnancies (26,631 in the induction group and 54,520 expectantly managed), were included in the analysis. Six of the included studies were randomized clinical trials with the remaining two being observational and retrospective cohort studies. Induction of labor was not associated with a significant increased risk of cesarean delivery (OR 0.97, 95 % CI 0.86-1.1), assisted vaginal delivery (OR 1.12, 95 % CI 0.96-1.32) or postpartum hemorrhage (OR 1.11, 95 % CI 0.88-1.41).

DISCUSSION

The belief that induction of labor is associated with an increased risk of cesarean delivery is based on the results of retrospective studies comparing induction with spontaneous labor at the same gestational age. However, at any point in a pregnancy, the comparison should be between induction of labor and expectant management, with the latter contributing to a pregnancy of greater gestation age and not always leading to spontaneous labor. When comparing induction to expectant management, our study shows no significant increase of cesarean section, assisted vaginal delivery or postpartum hemorrhage. Our study was not powered to assess neonatal outcomes, and additional research is needed to confirm whether induction of labor might have a positive effect in preventing stillbirth.

CONCLUSION

Induction of labor at term in advanced maternal age has no significant impact on cesarean delivery rates, assisted vaginal delivery or postpartum hemorrhage, giving additional reassurance to obstetricians who would consider this intervention in this particular subgroup.

Cesarean section rate is a matter of maternal age or parity?

OBJECTIVE

To determine the impact of women's age on the cesarean section (CS) rate according to Robson groups 1, 2A, 3 and 4A.

STUDY DESIGN

Retrospective cohort study of term, livebirth, singleton pregnancies with spontaneous or induced labor who delivered at the San Paolo Hospital from 1996 through 2019, and had the Robson group assigned. Women were grouped in 5 age classes (≤24, 25-29, 30-34, 35-39 and ≥40 years). The primary outcome was the rate of CS.

RESULTS

24 843 women were included: 36.4% classified as Robson group 1, 18.9% as Robson group 2A, 34.4% as Robson group 3 and 10.2% as Robson group 4A. The CS rate of women in Robson groups 1, 2A, 3 and 4A was 6.6%, 21.8%, 1.6% and 4.3% respectively. In nulliparous women [Robson groups 1 and 2A] group 1, the adjusted OR of CS increased steadily from 30 to ≥40 years, when compared to women aged 25-29 years. On the contrary, in multiparous women [Robson groups 3 and 4A] significant increased OR were present only for women ≥40 years. In young women [≤24 years] there was a significant reduction in the number of cesarean sections only in Robson group 1.

CONCLUSION

The results of our study show that multiparous women aged ≥40, either in spontaneous or induced labor have an independent twofold increased risk of delivering by cesarean section when compared to women of 25-29 years. On the contrary, in nulliparous women, the risk slightly, but significantly, increases with age and again becomes twofold in women ≥40 years.

Risk of adverse pregnancy outcomes of late- and postterm pregnancies in advanced maternal age: A national cohort study

Introduction

There is an increase in women delivering ≥35 years of age. We analyzed the association between advanced maternal age and pregnancy outcomes in late‐ and postterm pregnancies.

Material and methods

A national cohort study was performed on obstetrical low‐risk women using data from the Netherlands Perinatal Registry from 1999 to 2010. We included women ≥18 years of age with a singleton pregnancy at term. Women with a pregnancy complicated by congenital anomalies, hypertensive disorders or diabetes mellitus were excluded. Composite adverse perinatal outcome was defined as stillbirth, neonatal death, meconium aspiration syndrome, 5‐minute Apgar score <7, neonatal intensive care unit admittance and sepsis. Composite adverse maternal outcome was defined as maternal death, placental abruption and postpartum hemorrhage of >1000 mL.

Results

We stratified the women into three age groups: 18‐34 (n = 1 321 366 [reference]); 35‐39 (n = 286 717) and ≥40 (n = 40 909). Composite adverse perinatal outcome occurred in 1.6% in women aged 18‐34, 1.7% in women aged 35‐39 (relative risk [RR] 1.06, 95% confidence interval [95% CI] 1.03‐1.08) and 2.2% in women aged ≥40 (RR 1.38, 95% CI 1.29‐1.47), with 5‐minute Apgar score <7 as the factor contributing most to the outcome. Composite adverse maternal outcome occurred in 4.6% in women aged 18‐34, 5.0% in women aged 35‐39 (RR 1.08, 95% CI 1.06‐1.10) and 5.2% in women aged ≥40 (RR 1.14, 95% CI 1.09‐1.19), with postpartum hemorrhage >1000 mL as the factor contributing most to the outcome. In all age categories, the risk of adverse pregnancy outcomes was higher for nulliparous than for multiparous women. The risk of adverse outcomes increased in both nulliparous and parous women with advancing gestational age. When adjusted for parity, onset of labor and gestational age, advanced maternal age is associated with an increase in both composite adverse perinatal and maternal outcomes.

Conclusions

The risk of adverse pregnancy outcome increases with advancing maternal age. Women aged ≥40 have an increased risk of adverse perinatal and maternal outcome when pregnancy goes beyond 41 weeks.

Influence of maternal age in mode of delivery after term induction of labor

Objective: To determine the impact of maternal age on the rate of cesarean delivery in women undergoing induction at term.Study Design: Retrospective cohort study of term singleton gestations in nulliparous women induced for any indication at Lehigh Valley Health Network from July 2010 to July 2013. Exposure of interest was maternal age. Primary outcome was cesarean delivery. For every one woman ≥35 years of age (exposed), 2-3 women <35 years of age were selected as unexposed subjects for comparison. Statistical analysis included bivariate and multivariable techniques.Results: 406 patients were included; 101 women ≥35 years of age and 305 women <35 years of age. Women in the ≥35 group were more likely to be induced for maternal medical conditions and less likely to be induced for prolonged pregnancy; few inductions were elective. Few women were induced electively in either group. More than half of women in both groups required cervical ripening. Method of cervical ripening and/or induction and percentage of women with a Bishop score <5 were similar between groups. The primary outcome, cesarean delivery, was similar between groups (45.5% in age ≥35 group vs 40.0% in age <35 group, p = .33). After adjustment for potential confounders, the rate of cesarean delivery was not influenced by maternal age (AOR 1.21 [0.76, 1.91], p = .42) but was higher in women with a Bishop score <5 at the time of induction of labor [AOR 1.64 [1.09, 2.47], p = .02].Conclusion: In the wake of several recent trials underscoring the safety and potential maternal and fetal benefit of labor induction, identifying predictors of induction success (and failure) takes on increasing importance. Our findings suggest that maternal age is not an independent risk factor for cesarean delivery in women undergoing induction.

Women's experiences of decision-making and attitudes in relation to induction of labour: A survey study

BACKGROUND

Rates of induction of labour have been increasing globally to up to one in three pregnancies in many high-income countries. Although guidelines around induction, and strength of the underlying evidence, vary considerably by indication, shared decision-making is increasingly recognised as key. The aim of this study was to identify women's mode of birth preferences and experiences of shared decision-making for induction of labour.

METHOD

An antenatal survey of women booked for an induction at eight Sydney hospitals was conducted. A bespoke questionnaire was created assessing women's demographics, indication for induction, pregnancy model of care, initial birth preferences, and their experience of the decision-making process.

RESULTS

Of 189 survey respondents (58% nulliparous), major reported reasons for induction included prolonged pregnancy (38%), diabetes (25%), and suspected fetal growth restriction (8%). Most respondents (72%) had hoped to labour spontaneously. Major findings included 19% of women not feeling like they had a choice about induction of labour, 26% not feeling adequately informed (or uncertain if informed), 17% not being given alternatives, and 30% not receiving any written information on induction of labour. Qualitative responses highlight a desire of women to be more actively involved in decision-making.

CONCLUSION

A substantial minority of women did not feel adequately informed or prepared, and indicated they were not given alternatives to induction. Suggested improvements include for face-to-face discussions to be supplemented with written information, and for shared decision-making interventions, such as the introduction of decision aids and training, to be implemented and evaluated.

A systematic scoping review of clinical indications for induction of labour

BACKGROUND

The proportion of women undergoing induction of labour (IOL) has risen in recent decades, with significant variation within countries and between hospitals. The aim of this study was to review research supporting indications for IOL and determine which indications are supported by evidence and where knowledge gaps exist.

METHODS

A systematic scoping review of quantitative studies of common indications for IOL. For each indication, we included systematic reviews/meta-analyses, randomised controlled trials (RCTs), cohort studies and case control studies that compared maternal and neonatal outcomes for different modes or timing of birth. Studies were identified via the databases PubMed, Maternity and Infant Care, CINAHL, EMBASE, and ClinicalTrials.gov from between April 2008 and November 2019, and also from reference lists of included studies. We identified 2554 abstracts and reviewed 300 full text articles. The quality of included studies was assessed using the RoB 2.0, the ROBINS-I and the ROBIN tool.

RESULTS

68 studies were included which related to post-term pregnancy (15), hypertension/pre-eclampsia (15), diabetes (9), prelabour rupture of membranes (5), twin pregnancy (5), suspected fetal compromise (4), maternal elevated body mass index (BMI) (4), intrahepatic cholestasis of pregnancy (3), suspected macrosomia (3), fetal gastroschisis (2), maternal age (2), and maternal cardiac disease (1). Available evidence supports IOL for women with post-term pregnancy, although the evidence is weak regarding the timing (41 versus 42 weeks), and for women with hypertension/preeclampsia in terms of improved maternal outcomes. For women with preterm premature rupture of membranes (24-37 weeks), high-quality evidence supports expectant management rather than IOL/early birth. Evidence is weakly supportive for IOL in women with term rupture of membranes. For all other indications, there were conflicting findings and/or insufficient power to provide definitive evidence.

CONCLUSIONS

While for some indications, IOL is clearly recommended, a number of common indications for IOL do not have strong supporting evidence. Overall, few RCTs have evaluated the various indications for IOL. For conditions where clinical equipoise regarding timing of birth may still exist, such as suspected macrosomia and elevated BMI, researchers and funding agencies should prioritise studies of sufficient power that can provide quality evidence to guide care in these situations.

Induction of labour indications and timing: A systematic analysis of clinical guidelines

BACKGROUND

There is widespread and some unexplained variation in induction of labour rates between hospitals. Some practice variation may stem from variability in clinical guidelines. This review aimed to identify to what extent induction of labour guidelines provide consistent recommendations in relation to reasons for, and timing of, induction of labour and ascertain whether inconsistencies can be explained by variability guideline quality.

METHOD

We conducted a systematic search of national and international English-language guidelines published between 2008 and 2018. General induction of labour guidelines and condition-specific guidelines containing induction of labour recommendations were searched. Guidelines were reviewed and extracted independently by two reviewers. Guideline quality was assessed using the Appraisal of Guidelines for Research and Evaluation II Instrument.

FINDINGS

Forty nine guidelines of varying quality were included. Indications where guidelines had mostly consistent advice included prolonged pregnancy (induction between 41 and 42 weeks), preterm premature rupture of membranes, and term preeclampsia (induction when preeclampsia diagnosed ≥37 weeks). Guidelines were also consistent in agreeing on decreased fetal movements and oligohydramnios as valid indications for induction, although timing recommendations were absent or inconsistent. Common indications where there was little consensus on validity and/or timing of induction included gestational diabetes, fetal macrosomia, elevated maternal body mass index, and twin pregnancy.

CONCLUSION

Substantial variation in clinical practice guidelines for indications for induction exists. As guidelines rated of similar quality presented conflicting recommendations, guideline variability was not explained by guideline quality. Guideline variability may partly account for unexplained variation in induction of labour rates.

Inflammation induced preterm labor and birth

Preterm birth which occurs before 37 weeks gestation is one of the most common obstetrical complication in humans. After many studies, it appears that "not one answer fits all" regarding the risk factors, causes and the treatments for this syndrome. However, it is becoming more evident that one of the major risk factors is inflammation and/or infection in the fetoplacental unit. In animal models (usually consisting of mice injected with lipopolysaccharide at 14 days of gestation), IL-22 and IL-6 have been identified as factors related to preterm birth. There are some clinical tests available to determine the risk for preterm labor and delivery, which can be identified before, during early, or at mid-gestation. However, treatment of preterm birth with antibiotics so far has not been "curable" and studies using anti-inflammatory treatments are not readily available. More studies regarding causes and treatments for preterm labor and delivery in humans are necessary to prevent neonatal deaths and/or developmental abnormalities associated with this common syndrome.

The effect of maternal age on fetal and neonatal mortality

OBJECTIVE

Determine the gestational age at which the risk of fetal or neonatal death associated with delaying delivery by 1 week exceeds the risk of neonatal death associated with immediate delivery, stratified by maternal age intervals.

STUDY DESIGN

We conducted a retrospective cohort study of live births, stillbirths and neonatal deaths that occurred in the United States between 2010 and 2013 using birth data. Women were classified into six age categories. Singleton, non-anomalous pregnancies without hypertensive disease or diabetes were included. Relative risks were obtained using a generalized linear model comparing the rate of death associated with immediate delivery to those of expectant management.

RESULTS

For all age groups with the exception of women 44 years and older, immediate delivery was associated with lower relative risk of death by 39 weeks. For <25, 25 to 29, 30 to 34, 35 to 39, 40 to 44, odds ratios (OR) and confidence intervals (CI) were 1.0 (0.32 to 3.10), 0.67 (0.19 to 2.37), 0.80 (0.21 to 2.98), 0.67 (0.19 to 2.36) and 0.45 (0.16 to 1.31), respectively. In women 44 years and older, immediate delivery was associated with a lower relative risk of death by 38 weeks (OR: 0.35, CI: 0.14 to 0.90).

CONCLUSION

Women greater than 44 years old may benefit from delivery by 38 weeks gestational age to reduce the risk of stillbirth.