‘We had our twelve week scan and saw our baby! Everything is looking ok, but they changed our due date! Which is funny, because we know when we conceived!’
This is a tale I hear all too often! Certainly a possibility if your date is pushed back a little, maybe you ovulated later than you thought… but often, the *new* date is a scientific impossibility.. if you catch my drift!
It doesn’t end there.. let’s play a quick game!
I want you to jump on an imaginary private jet and take a quick trip to France. In France babies are ‘ALWAYS EARLY’.. Take your current EDD, add 7 days. THIS is you due date if you lived in France.
The physiology of French pregnant women is no different, and actually the management of a 42 week pregnancy isn’t much different either. But it would certainly have an impact on expectations of parents and reduce the pressure and anxiety felt by mums who are ‘late’.
So I thought it might be helpful to have a look at where due dates actually come from.. and what this might mean for you choices around birth.
In the UK we base our calculations of due dates on something known as Naegele’s Rule- This rule assumes you have a 28 day menstrual cycle, and that you ovulate on day 14. (True for some women of course, but certainly not all).
To calculate your EDD according to Naegeles rule, you count forward 40 weeks from the first day of your last period. (So for the first 2 weeks of pregnancy, you aren’t pregnant at all!)
Got it? Sounds ok right? But what IS this rule and where did it come from?
In 1744 a doctor in the Netherlands explained how to calculate a woman’s due date. Based on the records of 100 women.. (yes, you heard this right, 100 women.. in 1744.. I know!).. he said we should add 7 days to the last period, and then add nine months.
Noticed a flaw yet? I’ll help you! The doctor never stated whether we should add 7 days to the first day of the last period, or the last! Now, in 1812 Naegele added some thoughts of his own and this is where we get Naegele’s Rule, again not stating which day of your period this time should be added to. Until around 100 years ago, it was always added to the last day of your period, but for an unknown reason, it’s now the first! We've potentially lost a week in the turn of a century!
Current research has shown that a dating scan between 11-14 weeks of pregnancy is more accurate than the above rule when estimating your due date, but it’s certainly not fool proof. And since only 4% of babies are actually born ON their due dates, you can take that as a pretty strong indication that for 96% of you, that date youve etched in your mind, in your calendar, in your phone diary... probably won’t be you baby’s birthday!
Ok, it’s all very fascinating.. but you want to know when your baby will arrive right?
Unfortunately I can’t help you there, only you baby knows their birth day! But a more recent and much bigger study might be helpful for managing your expectations!
In 2001, a study into the pregnancies of 1514 women showed that for first time mums 50% had given birth by 40+5 (Meaning 50% were still pregnant at this point) and for subsequent births 50% had given birth by 40+3. 75% of first time mums had given birth by 41+2 and second time mums by 41 weeks.
Certainly food for thought! If you’re approaching the latter end of your pregnancy, I always encourage clients to think of their baby arriving in a ‘due window’, rather than on a certain date. Between 37-42 weeks you are considered to be ‘full term’, and your baby may happily arrive at any point during that window. If you’re approaching 42 weeks or later, you may be presented with the option of an induction.. but that’s a whole new post for a whole new day! Do your research and know that it is just that, a CHOICE.
For more tips for a positive birth, interesting info and a supportive group of mums to be- join our facebook group The Positively Birthing Space.
For a more in depth look into due dates this site is fab! https://evidencebasedbirth.com/evidence-on-inducing-labor-for-going-past-your-due-date/
To read more hints and tips for a positive birth experience read more here.
If you are interested in taking the next step to a positive birth, Positively Birthing Hypnobirthing and Antenatal Classes run throughout Surrey and SW London- areas including Surbiton, Esher, Teddington, Cobham, Twickenham, St Margarets, Thames Ditton, Molesey, Richmond, Wimbledon, Kingston, Sunbury, Epsom, Ewell, and beyond. All bookings can be made here.