Im confused with my dating?

[BabyCleo]

Hello On Dec. 22 we went for our 18-20week scan. I thought I was 17w5d. (I know, early, but I wanted to know gender and my dr said it was okay lol) but when I got there she told me they were going by my NT scan which would make me 17w1d. My NT scan I actually had to go back cause baby didn't co-operate, but she told me I was measuring ahead (hence 17w5d, not 17w1d) but this other tech (who was much nicer and showed us lots about baby) told me I was 17w1d. I have to go back in 2 weeks anyway cause baby was having none of it, but she told me im having a girl.

So, as of today I thought I was 18w2d, but according to the most recent tech im 17w5d.

Just to be clear: baby wasn't measuring late according to them. Apparently the old NT scan tech told me I was ahead when really, I wasn't. What do I believe?

 

[LadyBug923]

I would go by the date that you were originally given and the date that coincides with your LMP. All babies grow different, going through massive growth spurts or maybe just naturally a little smaller. If she thought baby was measuring 17+5 when you were really 17+1 I would just take that as a big healthy baby. Not that the actual dates were wrong.
I would ask your doctor to clarify how that works when you go see them next.
Congrats on finding out your having a girl, btw!

 

[BabyCleo]

Thanks!!! Ill ask my doctor when I see her next. The tech told me there is usually a 4 day error gap cause its impossible to get an exact date, so I guess either way im within range

 

[LadyBug923]

That makes sense. If I remember correct with my last ultrasound I was 7+5 by my LMP date. There were two dates on the screen so I asked the tech about it. She said the sac measured 7+5 and baby measured 7+1. She said they go by the both of them pretty much and as long as it is within a couple days of your LMP date it's totally normal. So that 4 day rule you spoke about would apply there, I suppose!

 

[Button#]

I'd personally go by scan dates as that's what my midwife would go by. If you go by the later due date it also gives you a bit more time once you get to due date if baby's not ready to come out before they start suggesting induction.

 

[Maidenet]

I got put back three weeks at my twelve week scan xx

 

[dom85]

I was put back 4 days as well at our NT scan so by my dates I'm due on the 14th April but by the scan it's the 17th. My midwife hasn't actually changed anything in my notes because she said its a lot of paperwork for the sake of four days.

 

[BabyCleo]

Thanks! I guess ill go by an estimate lol.

That does make sense about the induction thing, that's a really good point.

 

[misspriss]

Scans in the first trimester have 4-6 day margin of error. I have read that by 20 weeks, it can be up to 2 weeks off, and up to 3 in the third trimester. I would go by what they told you at your earliest scan.

My LMP put me due 5/24, my O date 5/29, and my first scan 5/28 (pretty close to O date) and my 20 week put me at 5/30, so my O date estimate of 5/29 was pretty spot on. Its all really close though so I haven't even said anything to my doctor. If they try and give me crap about going over, I will direct them to my scan reports.