Dates question - might be silly

[ella]

Hi Ladies,

There is something I dont really understand. They say calculate your dates from the 1st day of your last period, but then you dont ovulate for 14 days (ish), so then you find out your pregnant and you work out your weeks as advised. Then (well in my case and some others from what I can gather) you have a scan and they tell you that you are 1-2 weeks behind where you thought you were. So this must be the case for most people, i.e when your 5 weeks your really 3 etc. What I am wondering is when you look up what is supposed to be happening from week to week do you go by the original date (you last period) or the date the scan indicated????????

Or am I just looking too deep into it ???

Thanks
Ella

 

[mandspice]

I'm a bit confused on this too but I think the pregnancy duration is 40 weeks from the first day of your last period - so 6 weeks should be 6 weeks from the day of your last period also - I think!

 

[Hells]

Basing your due date on the 1st day of your last cycle is only exact for women who have a 28 day cycle and ovulate on day 14. Many women's cycles are not like this. The dating scan will give you the most exact age of your baby and may change your due date if it is quite different to the one based on your cycle.

The scan date is the exact one and the one you should go by. All pregnancy books should account for the 'extra' two weeks. To be precise, pregnancy should last 266 days (38 wks) from conception. The date from a scan will work out how old your baby is, then will add 2 weeks to bring the total up to 40 weeks.

If you thought you were 12 wks pg, but the scan said 10 weeks pg, then you would look at 10 wks in the pg books. This means your baby will be 8 weeks old + the extra two weeks they add on to make a full menstral cycle.

Clear as mud, huh?

 

[ella]

Thanks hells that is brilliant, and all I needed to know!