Discussion
Principal findings
This study analysed expectant management versus induction of labour at 39 weeks of gestation in women 40 years of age or older at the time of delivery. In older women, active labour management resulted in better perinatal outcomes without increasing the caesarean section rate and with similar vaginal delivery rates compared to expectant management.
Results in the context of what is known
The number of published studies on pregnant women of advanced maternal age is scarce. Most of the studies on induction of labour at term involved women with established complications, such as hypertensive disorders8 rupture of membranes9, foetal growth restriction10,11, diabetes12, or foetal macrosomia13. The 35/39 study was a randomised clinical trial designed to test the hypothesis that induction of labour at 39 weeks of gestation would reduce the rate of caesarean delivery among nulliparous women of advanced maternal age. Their data showed that induction of labour at 39 weeks of gestation, as compared with expectant management, did not increase caesarean delivery.14
The study by Knight et al included a total of 77,327 women aged 35 years. They found no statistically significant difference in the caesarean section rate between the 39-week labour induction groups and the expectant management group (Adjusted relative risk: 1.04, confidence interval [CI] 95%: 0.99–1.01).15 In 2019, a retrospective cohort study including 35-year-old nulliparas with singleton gestations at term comparing elective induction at 37, 38, 39 and 40 weeks’ gestation and those with expectant management at the same number of weeks found that induction at 39 weeks’ gestation was associated with decreased odds of caesarean section delivery (Ora 0.69; CI95%, 0.53-0.91).16 Our data supported previous studies and found no statistically significant difference in the type of delivery between the expectant management group and the induction at 39 weeks group. In the secondary analysis of the type of delivery according to parity, we found no significant differences in the route of delivery among the groups studied. In the expectant management group, the subgroup of women aged 40 years at 39 weeks of gestation and without any previous type of delivery (vaginal or caesarean) included 227 patients, of whom 24.2% had vaginal deliveries and 41.4% had operative vaginal deliveries. This meant that 65.6% of deliveries were vaginal delivery versus 34.4% of deliveries by caesarean section. In the active management group, the group of patients with the same characteristics was made up of 252 women, of which 69% delivered vaginally (32.9% vaginal delivery and 36.1% operative vaginal delivery) as opposed to 31% of deliveries by caesarean section.
Our data showed a rate of successful TOLAC similar to the 62.3% reported in previous studies.17
Another main finding was better neonatal outcomes in the labour induction group than in the expectant management group. The need for paediatric support at birth, the type of neonatal resuscitation measures, and the NICU admission rates were lower in the labour induction group than in the expectant management group. These data support the results of study lines in which perinatal outcomes improved with elective induction at 39 weeks of gestation.16,18
Finally, another result to highlight is the 0% stillbirth in the active management group versus the two intrauterine foetal deaths recorded in the expectant management group. These differences were not statistically significant because intrauterine foetal death is a rare adverse outcome, and a large sample size would be needed to find significant differences between the groups.
Research implications
There is a continuous risk for both the mother and baby with increasing maternal age, with numerous studies reporting multiple adverse foetal and maternal outcomes associated with advanced maternal age. Women ≥ 40 years of age had a similar stillbirth risk at 39 weeks of gestation with younger women at 41 weeks of gestation. Induction of labour at 39 weeks of gestation reduced these adverse outcomes. However, at present, there are insufficient data available on the effect such a policy would have on caesarean rates and perinatal outcomes, specifically in older women. Our study analysed the effect of labour induction compared with expectant management in women over 40 years of age. Our results provided data on intrapartum complications, mode of delivery, neonatal morbidity, and late stillbirth.
Strengths and limitations
Our study has several limitations. The definition of advanced maternal age in the literature varies with publications using different criteria. The definition used in our study aligns with the hospital’s definition of ≥40 years. The major limitation of our study was its retrospective nature. The retrospective dataset was subject to incomplete data entry and variation in practice. Despite our limitations, there are only a few studies in the literature that evaluated obstetric and perinatal outcomes according to active or expectant management in pregnant women of advanced maternal age and consider parity within their data.