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Your Pregnancy Does Not Have A Best Before Date!


Lets talk about EDD. (Estimated Due Dates).


Where did they come from?

Well, back in the 19th century, Franz Naegle, a German Obstetrician, calculated EDD'S by adding 7 days and 9 months to the last day of a woman's period. This became known as #Naeglesrule


So what is wrong with this calculation?


Put simply, one rule does not fit all. We are all different and our pregnancies are all different.

Naegle's rule does not take into consideration the following factors;

  • The duration of your MENSTRUAL CYCLE. How many people do you know have a 28 day cycle and ovulate on day 14?

  • Your Age.

  • Your Genetics.

  • The Father's Genetics. (Yes, these matter too).

  • Your weight and height.

  • Previous pregnancy duration.


Therefore, Lawson et al (2021), suggests this rule should be used as a GUIDELINE.


The problem is, once past 40 weeks of pregnancy, (or sooner), maternity staff start talking about INDUCTION for post dates!


"Birth works best when babies get to decide when they are ready to be born." Wickham (2022).


What about Due dates given from Ultrasound scans?


Ultrasound due dates are calculated by the size of baby and the length of pregnancy.

But this is flawed too.

Babies in the womb grow at different rates at different times, just like children do.

In a class of 5 year olds, no two children have grown at the same rate, and it is the same for a clinic of women having their 12 week scans.


Technology has its limitations.


Some Facts.


5% of babies are born on their EDD.

66% of babies are born from 7 days before to 7 days after their EDD.

1/3rd of babies are born before 39 weeks and after 41 weeks.


1/6th of women's due dates were wrong by more than one week when calculated by Ultrasound. kurlinge et al. (2016).


A Little Bit About INDUCTION of Labour.


The subject of #induction of labour is huge! Too big to cover in this short blog.

I cannot recommend enough the book "In Your Own Time" by Dr Sara Wickam.


Lets talk about induction for #postdates ,that is, past 40 weeks. Being postdates is the most common reason for being induced.

Approximately 1 out of 3 pregnancies are induced, up from 1 out of 5 ten years ago!


We know that a normal healthy pregnancy is #term from 37 weeks to 42 weeks. So why is induction offered before 42 weeks?


One reason women are advised to have an induction is because of a perceived concern that the placenta will suddenly fail after 40 weeks. This suggests your pregnancy does have a BEST BEFORE DATE of 40 weeks!! Your body doesn't suddenly stop nurturing your baby the day you are 40 weeks pregnant!


There is such a thing as placenta failure, but it is very rare and can actually happen at anytime during a pregnancy.


Another reason is the predicted risk of #stillbirth.

In fact, the increased risk of still birth at 41-42 weeks of pregnancy is tiny.

From less than 1 in a 1000 to 4 in a 1 000. (0.4%).


There are lots of studies out there proving or disproving these risks.

Much of the evidence is substandard and flawed, and no two studies have been carried out with identical criteria.

Some of these studies are also more than 20 years old. Advances in maternity care, better monitoring of babies etc, have come a long way since they were published.


It is always possible to find evidence to support your views, on any subject, so it is important to look at several, or read a book like #sarawickham to get a rounded, non-bias view.


INDUCTION of Labour has its own risks.


If you are going to be induced for being past your EDD, you might want to consider the effect it could have on you and your birth experience.


  • Increased risk of needing an #epidural

  • Increased risk of needing an assisted birth, such as #forceps or #ventouse.

  • Increased risk of having a #caesarean birth., depending on when you are induced.

  • Increased risk of Infection.

  • Baby has an increased risk of Jaundice.

  • You could have an increased risk of #Postnataldepression.

There could also be a negative effect on your physical and mental health and feeding journey, but studies are limited.


And Finally...


There are other reasons for induction of labour being offered. These have their own risks and benefits. These include maternal size, maternal age, IVF pregnancy, suspected big baby, ethnic origin. I have focused on due dates for this blog.


You always have a choice.


Seek advise from your midwife, birth worker or Doula.


There are valid reasons for needing an induction. Concerns for your or your baby's health for example.


Inductions can be a positive experience if you are informed and knowledgeable. There are lots of positive induction stories out there, including one of my clients.


Please message me if you have any comments or concerns.












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