I thought that to find out a due date, the calculation would be quite simple. In the past I have always heard about the 40 weeks of pregnancy and assumed that there was an exact science around this. Obviously, I realise now, this is not the case. The popular method of doing this seems to be adding 280 days onto the start date of the Last Menstral Period (LMP). Unfortunately you have to know a few things first:
- How long on average the LMP is for the person – this can be erratic so the exact average may well be unknown.
- And that the ovulation will indeed occur exactly two weeks after that – but that is not a given, just an approximation.
So, the things you have to know, in most cases are variable – which of course makes any sort of calculation a bit hit and miss.
The pregnancy duration itself is 266 days after conception, plus with what I have mentioned above you can have a fair estimation of a due date if you have an idea of the conception date – but, there is yet another factor. Conception does not necessarily occur at intercourse. In fact, there is a 3 day window after intercourse for when conception can occur, which again makes things very changeable.
With all this in mind, the estimate given by using the LMP seems the most unreliable. Using the Conception method, you can at least get the date range down to 3 or 4 possible days .
In a nutshell, nature is not giving up its secrets, and there are two many variables for doctors to be able to get a due date exactly right. Saying that, they can get pretty near.
All this of course actually involves a fair amount of ‘assumptions’ and we all know what to ‘assume’ means.
“When you assume, you make an ass out of u and me” ~ Oscar Wilde on Assumption
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