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Having a planned birth? Every extra week counts.

27 Nov, 2023

Having a planned birth? Every extra week counts.

By Professor Jonathan Morris, Obstetrician, Royal North Shore Hospital/University of Sydney, Every Week Counts

Having a planned birth? Every extra week counts.

Twenty years ago, the majority of women gave birth at 40 weeks; today it's between 38 and 39 weeks and continuing to get earlier. The main reason for this shift is the growing proportion of planned early births that are happening at 36, 37 and 38 weeks, either by induction of labour or by planned caesarean.

What's the big deal, you might ask? It's only a week or two. Surely that doesn't matter does it?

Many health professionals have thought the same.

But recent research in Australia and overseas shows that the risks of short and longer term problems increase for every week a baby is born early. Women and their care givers need to know about this new research.

Let's look at the shifting pattern of births

In the 1990s, women living in NSW were most likely to give birth at 40 weeks. Now the most common time is between 38 and 39 weeks. The biggest reason for this shifting pattern is that more planned births are happening before 39 weeks (see figure).

Why do women have earlier births?

There are lots of reasons why some women and their babies have an early birth, and in many cases this is necessary. Increased monitoring during pregnancy has helped doctors identify women with complications such as high blood pressure or gestational diabetes. Ultrasounds are more common than they used to be and help detect babies who might be small or not growing well. In these cases, a decision to have an earlier birth may be a safer option than letting the pregnancy continue. And up until recently, it was widely believed that being born a few weeks early carried little or no risk to the baby. Our special care nurseries and neonatal intensive care units can provide excellent care for babies experiencing early problems.

We used to think an early birth was before 37 weeks, but new evidence makes it clear that babies born at 37 or 38 weeks should also be thought of as early births because they are at increased risk of complications too.

What are the consequences of being born a little early?

Research from my own team and others has shown that an early planned birth has both short-term and long term consequences for the baby. For every week a baby is born before 39 weeks, the risks of problems increase. For example, the likelihood that the baby will need help to breathe steadily increases with each week of earlier birth. Difficulties with breastfeeding are also more common in babies born a little early.

What has been more surprising is the longer term impacts of earlier birth. Our research has shown that for every week a baby is born before 39 weeks, he or she is at increasing risk of developmental delay at school. We have looked at the association between when babies were born and how they performed in kindergarten. 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". This means they scored poorly on two or more test categories. The risk was higher for babies born after a planned birth compared with those who had a spontaneous birth. Our results are very similar to other research reported in South Australia.

What is happening to the baby in the last weeks of pregnancy?

Although many aspects of a baby's development are almost complete by 36 weeks, the final weeks of pregnancy are crucial for optimal brain development. At 35 weeks, the baby’s developing brain weighs about two-thirds of its final size at 40 weeks. In babies who are born early, the brain continues to grow but in a slightly different way. This impacts how the brain works, and why some differences are found in later school assessment results. Similarly, a baby’s lungs are not fully developed until around 39 weeks. This is why babies born before this time often have early breathing difficulties and may need oxygen.

What should we do in the face of this new research?

A healthy start to life is the greatest gift we can give to a child. Every parent wants to give their child the best possible chances in life. So one of the changes we can think about is the timing of planned births. For some women and babies with medical complications, the safest and best option will still be an early planned birth. But in other cases, women and their care providers planning the timing of birth should aim for birth as close to 40 weeks as possible. Quite simply, planned birth in the absence of any risk factors for mother or baby should not occur before 39 weeks. If we do this, we will reduce the likelihood of short-term problems and also improve children’s longer-term development.

Final words

The timing of a planned birth is an important decision to discuss with your doctor and family. If you can wait a little longer and it is safe, then do so because every week counts. Further information and a free brochure can be found at


Find out more about Every Week Counts at

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