Do you use your lmp or scan date for accuracy of your due date

[rccresswell]

Hi all

I know it's me again with another question.  I thought I would keep the forum alive lol.  I was just wandering what dates you use when dating your gestation.

When I went for my first scan based on my lmp I was 5 days out. Baby was 5 days younger and that was at 7 weeks 5 days.  When I went for my next scan the sonographer said baby was measuring 12 weeks but should have only been 11 weeks 3 days based on my last scan.  He said when do you think you are due and I said the 1 march but based on my lmp it should be 25 feb and he said that's it.  I was like oh ok and when I went to the doctor he wrote I was only 11 weeks 3 days yet on the scan baby measures 12 weeks.

I was like blimmin heck what is it.  I know there are only 4 or 5 days difference but I would like to think I am further ahead lol.  Have you had different dates based on your lmp and scan date and if so what date do you go by.  I know for a fact when I ovulated but I don't know if I should start counting from the Friday or Tuesday with every subsequent week.

I talked to my midwife about it and she said do go by the scan date because my period was out of whack because of the miscarriage.  She is like it's no big deal but you know how you get excited every time you start a new week, I want it to be sooner rather than later lol.

I guess another reason I am a bit worried about the difference is when I had my son at my first scan he only measured 9 weeks when he should have been 11.  I went by the sonographer's date.  I had him 2 days early and after he was born my placenta was ripped to shreds, it was falling apart.  My midwife was baffled as to why my placenta was in such bad shape.  When I had my daughter I was 12 days early and her placenta was perfect.

I guess it is all wait and see.  Do you go by your lmp or the scan date.

Sorry about the long confusing story lol

[spiritwolf31]

Officially my doc is going on the u/s scan size at 8wks cuz the baby measured exact to the lmp date. That is funny though cuz the further you get...the bigger the baby measures. At 36wks with my second son he measured 42wks but oc I am diabetic and he was a large baby. My due date is officially March 3 but doc is already planning on C-section week and half early unless baby starts to get too big in which we plan a 3wk early delivery sooo...although March due date he/she will be a February baby   ^_^

[lil_lady25]

My doctor was the opposite and that they use the measurements of the babies. I guess in the first trimester babies grow at the same rate and thats how they determine how far along you are. That's what they did for me atleast. According to my lmp I am 5 days behind at 19w6d and by measurements I am 20w4d. At my 12 week appt they gave me a due date of Feb 9th but want to give a c-section at 36 weeks which will be January 9th. I guess every doctor is different!

[rccresswell]

Thanks for that, according to that I am 18 weeks now yayy!!!! lol.  I guess we will see when baby is born but I am guessing baby will be early although late would be nice lol

[SunWorshiper_26]

Ive been told go by lmp unless you know exact date you ovulated. By lmp they assume you ovulate on the 15th day of your cycle I know I ovulated 2 days after that so they used lmp plus added two extra days for the two days late I ovulated. The ultrasound dating isn't very exact I've been told. But I'm sure that there are other opinions. That's just my two cents ;)