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How to work out due date with no period before BFP?

(10 Posts)
moominlike Thu 23-May-13 07:29:36

Firstly please excuse my ignorance - this has kind of taken me by surprise and I can't get my head around how it all works!

So I read that when calculating how pregnant you are they actually date it from the first day of your last period. That seems odd to me as you won't have actually been pregnant from that day?! So is your due date it then 40 weeks from that day?

I didn't have a period between coming off the pill and getting a positive test so how will they work out my due date?


TinkyPeet Thu 23-May-13 07:36:15

That is the way they normally do it yes, but in your case I would imagine they will wait a few weeks and sen you for a dating scan, provided you dot think you are any more than 8 weeks? X

TinkyPeet Thu 23-May-13 07:36:58

Sorry, send* don't* iPhone spelling is horrible lol x

girlonfire Thu 23-May-13 07:59:17

Yes, I had the same, a dating scan was done to estimate a due date.

moominlike Thu 23-May-13 08:27:42

Definitely not 8 weeks as I had only been off the pill for 3 weeks when I got my BFP and clear blue digital said 1-2 weeks pregnant. So I guess I just count 38 weeks from 1-2 weeks ago as a rough idea? Cos counting from your period effectively adds 2 weeks on?

When did you have your dating scan girlonfire?

rubyanddiamond Thu 23-May-13 08:41:26

Something similar happened to me when I had the mirena removed. The midwife took two weeks off the date it was removed, and initially put that as the due date. Based on that I was sent for a scan at 12 weeks, but that showed I was only 10 weeks so I had another scan a couple of weeks later.

I think if you explain at the booking in appointment (the first one with the MW) then she'll try and make sure you have a scan early enough.

RoomForALittleOne Thu 23-May-13 08:54:02

I had very erratic periods because of BFing when I conceived DS. I told the midwife that and the date that we had ditched contraception plus when I got a BFP. We had a guess at rough dates and they were very close to the dating scan date (only two days apart) so they were happy to stick with the initial dating scan date.

TinkyPeet Thu 23-May-13 08:54:05

Clear blue 1-2 is what docs put you as 3-4 weeks so add 36 weeks from now. So they will probably arrange your dying scan for about 6-8 weeks time x

katemeister Thu 23-May-13 10:32:29

Same happened to me recently, when I went to see the nurse we worked on basically my last day of the pill being my LMP so came up with a due date ~5th Dec. Because of the uncertainty I was sent for a dating scan at 9 weeks which gave me an EDD of 10th Dec. Oh and congratulations!

moominlike Thu 23-May-13 13:54:57

Thanks for all the advice, I think it's starting to click! 36 weeks from BFP is 27th Jan and 40 weeks from last day of pill is 1st Feb so that gives me a good idea!

All very exciting!

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