Pregnancy length - 40 weeks and 3 days?????

[AskABusyPerson]

Both my sister and I are pg (me 10 weeks, she 12 weeks) and live in same county but 25 miles apart so different docs and midwives. She said her midwife and doctor calced her due date by adding 40 weeks and 3 days to LMP. Mine added the expected 40 weeks. All internet sites I've looked at do 40 weeks and my midwife said 'yes they are accurate' when I said I'd calced my edd from internet site!

Anyone else ever had 40 weeks and 3 days length!!!?

Does she have a longer than average cycle ie 31 days? That would suggest that she normally ovulates on day 17 instead of day 14, hence adding on an extra 3 days to her due date. (I think I've got that the right way round, does my head in!)

At the end of the day babies tend to arrive when they're ready anyway so due dates are only a guess anyway!

As Moo says due dates only only guestimates. Only a small proportion of babies arrive on their actual due date, can't remember the % but its not huge. Anything from 38 weeks onwards is counted as term anyway. You only really need to be concerned about due dates if it looks like you might need an induction. Personally I'd fight tooth and nail to avoid one but thats another thread...

Thanks, I guess I could ask her why but she stated it in such a matter of fact way as if that was the normal calculation!

I know edds are estimates, with my dd she was due 27th July, arrived by induction (yes, horrid) 19th July after waters broke on 17th July!

EDDs are based on the textbook regular 28-day cycle - which I suspect only a minority of women have. Mine, despite being very 'regular', has always varied between 25 and 30 days.

Maybe they were going with a scan result?