My firstborn’s birthday is statistically rare. He is one of only 4% of babies who are born on their ‘Estimated Due Date’.

What is an ‘Estimated Due Date’?

An ‘Estimated Due Date’ (EDD) is basically a prediction of when your body might go into spontaneous labour.  And it is just that – a prediction! In fact, it is not even evidence based!

How is your Estimated Due Date Calculated?

At your first midwife appointment, the baby’s EDD is calculated from the date of your last period + 40 weeks. However, the process assumes that all women have a 28 day cycle and ovulate on day 14. This, we know, is not true. It is likely that this ‘due’ date will then be changed when you go for your 12 week ‘dating’ scan where your EDD is then given based on the size of your baby.

Ultrasound image of a baby

I find this interesting, given that, as adult humans, we are all different shapes and sizes so could it not be true that babies are of a different size and weight at the same gestation? Interestingly, research shows that the gestation period also differs from woman to woman so why are we placing so much emphasis on this 40-week mark?

40 weeks actually originates from a small research study carried out on just 200 women back in the 17th century where the doctor concluded that pregnancy lasts 40 weeks – he didn’t state if this was 40 weeks from the beginning or end of your period or from the date of conception. Amazingly, not every country in the world calculates this date in the same way either so it is crazy that we, as women, feel so much pressure as our EDD looms. 

Newborn baby in man's hand

According to the World Health Organisation, full term is anywhere between 37 and 42 weeks (with many babies arriving perfectly healthy either side of this) so perhaps think of a due ‘window’.

Given that the majority (85%) of babies arrive after their Estimated Due Date, it may also be better to consider this date to be the date FROM which baby will arrive and adopt the attitude that baby will arrive when baby is ready. 

What to do as this ‘Due’ Date Looms?

Plan in events close to, on or even after your ‘due’ date. Waddle around in shops, like I did. Go out for meals. Arrange social events so you have things to look forward to and to take the pressure off. If you’re not able to attend because your baby has arrived well then your baby will be in the world so you’ll have other things on your mind and people will understand!


Get In Touch

Demelza Sayers - KGHypnobirthing Consultant
Tel: 07961 898215

Hypnobirthing classes in Cornwall and Devon or online via Zoom


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