Over the past two decades there has been a major change in birth practices that has resulted in a silent but steady shift towards women giving birth before 40 weeks.
Planned early births, either by inducing labour or by planned caesarean, have fuelled this shift.
Until recently, researchers had thought there were no long-term risks to babies born a little early. However, a growing body of evidence points to long-term developmental delay by the time these children reach school.
It’s time to rethink our attitude to early planned births and to advise women and their care givers that giving birth early carries long-term as well as short-term risks.
A shifting pattern
In New South Wales, in the mid 90s, a woman was most likely to deliver at 40 weeks. Now, between 38 and 39 weeks is the most common. During that time there has also been a year-on-year increase in the number of births between 34 to 39 weeks. Currently nearly one in five of all single babies born is at 38 weeks, one in 15 at 37 weeks and one in 40 at 36 weeks.
The rise in early planned birth is a result of both planned interventions because of concerns over the mother’s and/or baby’s welfare or, less commonly, for convenience.
Factors that have contributed to planned early births on health grounds have included increased ultrasound surveillance in pregnancy, which has increased the detection of babies who are small for their gestational age. The lack of sufficiently accurate tests to distinguish a healthy small baby from a small one that is compromised means these babies can be delivered early in the belief this is a safer option.
Another factor is that diabetes in pregnancy is more common, which can lead to problems at birth, such as the baby being very large or suffering from respiratory distress, or for the mother, such as high blood pressure and preeclampsia. So 37 weeks, or term, has become an accepted time for planned birth for these babies.
Planning to give birth early occurs in the belief that early delivery carries no significant risk to the baby or is safer for the mother and/or baby compared with continuing the pregnancy. Widely held views that it is safe for the baby to be born a few weeks early may lead to a decision for elective early birth for no medical reasons.
While much attention and research has focused on the short and long-term consequences of very early birth, there has been far less attention to the risks to babies born just a little early.
For many years, we have assumed babies born after 37 weeks gestation have no risk of problems. After all, the official definition of “term” has been classified as the period between 37 and 42 weeks of pregnancy.
However, there is no scientific basis for 37 weeks being recognised as the time when a baby is mature.
Short and long-term consequences
An early planned birth has consequences for babies, both in the short-term and, as researchers are discovering, in the long term.
We have described that every week a baby is born prior to 39 weeks increases the likelihood of the need for breathing support and admission to newborn intensive care. This is important as these babies occupy scarce resources that could be avoided if birth could be safely delayed by a week.
However, until recently, researchers thought there were no longer term effects of birth at 37 weeks or even from 34 weeks. That belief is changing.
In our study, we used routinely collected birth data for more than 150,000 children to determine how their development was associated with their gestational age and circumstances of birth.from www.shutterstock.com
We then looked at how these children performed when they started school using data from the Australian Early Development Census. This census, which kindergarten teachers take every three years, assesses children’s physical health and well-being, social competence, emotional maturity, language and cognitive skills, communication skills and general knowledge. These are associated with longer term health, education and social outcomes.
We found for every week a child was born earlier than 39 weeks there was a small but significant increase in the likelihood of them being developmentally vulnerable; they scored poorly on two or more of these categories.
The risk was higher for babies born after a planned birth compared with spontaneous birth. Our results are very similar to other data from South Australia.
These results tell us the final weeks of pregnancy are crucial for optimal brain development. Indeed the brain weighs two-thirds at 34 weeks of what it will weigh at 40 weeks. It is in the final weeks of development that many finer brain networks linked to developmental outcome are formed.
What we’d like to see
A healthy start to life is the greatest gift we can give to a child. Changes in birth practices need urgent reappraisal in light of population changes to early birth that have longer term developmental implications; the threshold at which we resort to planned birth needs careful rethinking.
Women and their care providers should aim for birth as close to 39-40 weeks as possible when considering early birth.
Elective planned birth in the absence of any risk factors should not occur before 39 weeks.
If there are special considerations in pregnancy such as a mother’s high blood pressure or diabetes, or the baby is found to be small, the aim should be to prolong the pregnancy for as long as it is deemed safe to do so.
This approach will not only reduce the likelihood of short-term problems but also improve children’s long-term development.
Jonathan Morris is an obstetrician who leads a large population health research group interested in optimising maternity services and outcomes. His work is supported by NHMRC and NSW Ministry of Health.
Authors: Jonathan Morris, Professor of Obstetrics and Gynaecology and Director, Kolling Institute of Medical Research Obstetrics, Gynaecology and Neonatology, Northern Clinical School, University of Sydney