A study carried out by researchers at the University of Amsterdam Medical Centres on more than 220,000 children examines the academic performance at age 12 of children born by induced labour. According to the authors, a reduction in scores was observed in infants born after induced labour between 37 and 41 weeks. The research is published in Acta Obstetricia et Gynecologica Scandinavica.
First, I would like to point out that the long-term impact of routine interventions in healthy people should be evaluated systematically, not only in the case of induction of labour. This requires recording the short- and long-term effects - desired and undesired - of interventions, in order to be able to make balanced decisions for or against the intervention. In this case, not only the physical but also the psychosocial consequences need to be taken into account. This study addresses these issues.
It is always problematic to interpret causal relationships from observational studies. We are dealing with secondary data, the quality of which cannot always be reliably traced, and which were collected in a completely different context. In addition, we are faced with a very long period of data collection: definitions of exclusion criteria, such as gestational diabetes, changed several times during this period at the international level. The document does not allow us to know which drugs were used to induce labour and in what doses, nor whether the approach changed over the period.
I would also like to underline the complexity of the factors that influence children's academic performance. It is true that this study did an excellent job of taking into account common variables, such as socio-economic status and parental education level. However, other possible factors - for example, the self-efficacy and resilience of pregnant women who refused induction of labour and the impact of such an attitude on offspring; the number of children, marital status, duration of breastfeeding, mode of delivery and others - cannot be taken into account.
In addition, induced deliveries more often involve the use of other drugs in labour that also have a psychosocial impact, such as oxytocin. To determine [whether pharmacological induction of labour may alter the neurodevelopment of children], prospective randomised experimental studies or at least matched observational studies over long periods of time would have to be conducted.
What impact might induction have on brain development?
Hypothetically, an influence on foetal brain development is conceivable. We know that children tend to benefit cognitively from a physiologically long gestation period, compared to preterm birth. There are fewer studies on the question indirectly raised by this study: could an artificially shortened gestation period by a few days - and not the drugs used for induction - have adverse effects on the child? If so, what are they and in which children?
A direct influence of the drugs used for labour induction (prostaglandins or non-placental oxytocin) on the brain development of the foetus has not been demonstrated so far and, in my opinion, is not plausible. The biological plausibility of adverse effects of routine induction of labour, within the physiological duration of pregnancy, might rather lie in the individual optimal maturity of some foetuses. Figuratively speaking, harvesting freshly ripened fruit or vegetables will have the advantage that there will be no further insect or weather damage to spoil the crop, but neither will the full flavour of sun-ripened fruit (and some will undoubtedly be unripe) be exploited.
What does the study add to the evaluation of the procedures currently practised?
The study adds to the body of knowledge on this subject and raises important questions. We urgently need to introduce strict monitoring and evaluation of the effects of routine interventions, especially in healthy people without medical indication. The essential questions here are: is the desired effect achieved (e.g. fewer stillbirths, fewer caesarean sections), what are the undesired effects (e.g. birth experience, child development)? On the issue of induction of labour there is conflicting and absent evidence.
This article has many strong points that advise a thoughtful review, which should be agreed by a large and heterogeneous group, impossible in a few days.
- They provide links to the protocol and the statistical analysis plan, which would make it possible to check whether the study is free of selective reporting bias (presenting the analysis with the results that suit them).
- They claim to analyse all births. If true, they would be free of the suspicion of selection bias - having eliminated cases for a variable that is a simultaneous consequence of the intervention and their cognitive development.
- They are aware of a possible confounding of residual effects - the differences come from other variables that are impossible to adjust for, perhaps because they cannot be determined with sufficient precision to be able to adjust for them.
That said, it is worth qualifying:
- They say they adjust for variables, such as maternal age or maternal education level, without detailing their functional relationship with the response, or how it was specified, or whether it was done ex post, again potentially falling into selective reporting bias.
- They acknowledge that they must interpret the results at the level of association, not causation ("our findings are limited to associations and do not necessarily imply causality"). But they consistently interpret it at the causal level (or seem to induce causality in the reader: "reduced long-term intellectual development in the offspring", "These longterm effects of induction of labor should be incorporated in counseling and decision making").
- The observed effect is minuscule: 0.05-SD means that it is one twentieth of the natural dispersion between cases in school performance. Such a (hypothetical) low effect will have a low impact. And because it is so low, it is much more likely to be explained by artefacts such as those discussed above.
- Like most observational studies, the calculations they present (such as uncertainty intervals) are based on the random sample assumption, which they do not meet.
- Research article
- Peer reviewed
- Observational study