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Why don't babies play by our rules? ..


Even years after the birth of my babies, I can still clearly remember their 'due dates' and the disappointment I felt when the sun set that evening and I had absolutely no sign of my labour starting with either of them. But, statistically only an estimated 4% of births in the UK actually occur on the calculated due date given, with approximately 1 in 5 babies born after 41 weeks of pregnancy.


The purpose of an estimated due date is to try to provide clinicians with an idea of when your little one is at the 40 week mark of pregnancy. This can then guide them with when to offer to intervene if there are any complications that arise, or if your baby isn't showing any signs of wanting to be born and you are having a prolonged pregnancy.


Your estimated due date can be calculated by various methods:


  • Most commonly in the UK the method used is by estimating your babies size from various measurements taken from an ultrasound scan. This in itself is subjective as it is a skilled technique that can very much vary slightly from sonographer to sonographer.

  • You can count 280 days from the first day of your last period - this formula is attributed to the German obstetrician Franz Naegele (1778-1851) and are what our well known obstetric wheels are based on today - a 19th century formula which allowed no room for variation on accounts of ethnicity, parity, lengths of menstrual cycles and genetic heritage (all factors we know today can affect the duration of a pregnancy).

  • You may have had IVF and have a known implantation date to help calculate a date.

  • You may have known when you ovulated and when you conceived.


What we know is that around 90% of pregnancies will naturally last between 37-42 weeks in length and this period is referred to as a "term pregnancy". After 42 weeks of pregnancy there is evidence to suggest that babies are at an increased risk of harm both of stillbirth and functional impairment. As such, national guidelines will advise women to be induced at 42 weeks of pregnancy if the woman isn't already in labour.



There is growing evidence that labour normally starts when a baby sends a chemical signal to the mothers body to say that they are ready to be born. It's possible that if your labour hasn't started, this is because your baby needs a little longer in the womb, certainly if the pregnancy is under 42 weeks of gestation.


In France the calculation of a woman's "due date" will add a further 7 days to their pregnancy. The physiology is no different, the actual management of a 42 week pregnancy is not much different, but the psychology is enormous and here's why...


When a woman arrives at the date given there is bound to be a sense of pressure to perform. Discussions around induction of labour often occur at planned routine midwife visits and there can be a sense of urgency that things need to happen soon to avoid intervention. Even by just classing yourself as "overdue" creates the suggestion that your baby is late and something is wrong. You can start to doubt your body and your stress levels can begin to increase - the exact opposite of what is needed to actually help stimulate labour. You can be plagued by well meaning messages from family and friends excitedly wanting to know if 'things are happening,' all adding to the volumes of disappointment and urgency you can place on yourself.


The irony is that we all see very well how once born, babies develop at different paces. Not all babies will teethe or walk at the same time, so why should they be born at the same time? A longer pregnancy may be entirely normal for some. To think of your baby arriving in a 'due window' between 37-42 weeks of pregnancy, knowing that it's highly likely by 42 weeks that you will have birthed your baby, can be a far healthier way of approaching your birth rather than fixating on the "due date" given.


Top Tips to manage pressure, stay relaxed and focus:

  • Do things that you enjoy. Take a bath, take a walk, share time with friends and family, watch your favourite film, bake or knit - whatever relaxes you and makes you happy.

  • Try to ignore your estimated due date. Instead, change emphasis to the concept of a 'window of birth' being anywhere between 37-42 weeks of pregnancy.

  • Re-direct well meaningful messages to your birth partner. Have conversations with friends and family if you can before 40 weeks informing them it's entirely normal for a pregnancy to extend past 40 weeks of pregnancy and that you are going to give little interest to this date, rather focus on preparing your body and mind for your labour.

  • Be mindful and be in the moment knowing that your time will come.

  • Remember that your body is enormously clever, trust your instincts and seek advice form experts if you are worried at any stage.


If you want to read more about inducing labour, see below links:


Induction of Labour | AIMSOverview |


Inducing labour | Guidance | NICE


Inducing labour - NHS (www.nhs.uk)












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