How accurate is your Due Date?

To put it simply, your estimated due date is just that. An estimated date that is not based on any real evidence. Let’s discuss…

In 1744 a professor named Herman Boerhaave looked at the records of 100 White European pregnant women and calculated an estimated due date. He did this by adding 7 days to their last period and then adding 9 months.

In 1812 a professor named Carl Nagele added some of his own thoughts to Professor Boerhaave’s due date theory which is how it got the name we use today. Neither professor explained whether the 7 days were added to the first or last day of the menstrual period.

Over the years Nagele’s theory has been interpreted by doctors in different ways. 7 days were added to the last day of the last period until the 1900’s when the 7 days were then added to the first day of the last period. Today almost all healthcare professionals use a form of Nagele’s theory to calculate your ‘due date’ with 7 days being added to the first day of your last period and then count forward 9 months. A rule that is not based on any concrete evidence.

Research shows today that 4% of babies arrive on their due date with 10% arriving before and 86% arriving after. It’s almost as if the due date is not correct!

Nagele’s theory assumes that each pregnant person has a 28 day cycle and ovulates on the 14th day. The theory does not take into account the varying length of menstrual cycles, ethnicity, medical history, socio economic factors or size of the pregnant person.

Being given a 40 week due date can lead to negative thoughts that you are ‘late’ if you go past this date. Each pregnancy is unique to the birther and their baby. Your baby will ultimately arrive when they are ready, this can be anytime between 37 and 42 weeks.

Resources:

https://evidencebasedbirth.com/evidence-on-inducing-labor-for-going-past-your-due-date/