Can a dating scan tell when you had sex?

[MummytoJ]

I'm just asking as my dates dont add up. My my dates changed after i got my dating scan but they dont match anytime me and my husband had sex. I just want to know does a dating scan know exactly when you conceived? I just dont want to end up getting induced

 

[StranjeGirl]

How early was your scan and was it vaginal? After 7-8 weeks they are accurate within a few days (have been dead on for me) but it really imply a when you ovulated as opposed to having sex. Sperm can live for a few days inside, and sometimes even up to 7 days days. So you may have had sex a few days before you ovulated and got pg, and then the scan can be off by up to a few days (more if its a very early scan)

 

[Mya209]

No a dating scan won't be that accurate that it can tell you when you had sex. My dates were off with my first as she had long legs (I'm 5ft 11 durrr!) they wanted me to change my due date but I stuck to my guns because I knew my dates were ok and she was just tall

 

[Tromboli]

They are an estimate, the earlier the ultrasound the more accurate the result. How far off are you talking? Weeks or days? Days won't effect you much. Weeks, maybe, but remember how far along you are is usually calculated from the last period date not conception date so 6 weeks is more like 4 weeks from conception.

This is a question you should probably ask the doctor, though

 

[Mya209]

Are they dating you from LMP though? Then it wouldn't be anything to so with when u had sex

 

[MummytoJ]

I thought i was 11 weeks and 6 days but was only 11 weeks 3 days which i know isnt much difference. I just wondered if it could tell exact conception date incase it was before of after we got married

 

[Mya209]

That's 3 days difference. Sounds like your dates are accurate to me.

 

[dan-o]

Mine were a week out both times, even tho I was on clomid and scanned at ovulation!

When ds2 arrived a fortnight early by my dating scan EDD, he was actually 3 weeks early by ovulation.

 

[BunnyN]

They say a scan between 10 weeks and 13+6 is accurate give or take 5 days. I'm sure mistakes are made sometimes too though.

 

[amyleigh89]

It would be dependant on how long fertilised egg took to travel down to your uterus as well. Could all be a few days out. Pretty hard to know exactly unless you know when you dtd. X

 

[Genevevex]

My first pregnancy they calculated it EXACTLY based on an early scan. We had sex ONE day that entire month, and that was the date of conception they came up with at the scan (I didn't tell them, I wanted to see what they said).

This one it could have been four different dates. They dated me on a day that settled on the middle date, the day after sex, the day I actually ovulated. Again, I said nothing, wanting to see what they came up with. So far, it seems pretty spot on. We'll see how much that stays by the next scan.

 

[lynnikins]

its all just an esitmate, my dates get shifted forward 3-7 days with each baby and yet they all end up coming late one 3 days when my date got shifted by 3 days so i reckon my LMP date was accurate not scan date. with my youngest my date was moved forward a whole week and he was born at 42+2 so I think my LMP again was more accurate as he didn't appear to be a 42wk baby he was more a 41wk week baby by his skin etc...

 

[Selaphyna]

With my first, I had the perfect 28 day cycle, LMP was May 2nd, we dtd May 16 & 17th. I was due for my period again May 30th, I tested on June 6th a week late. With that my EDD was Feb 5th. I didn't have any type of scan until 20 week, and according to his measurements, he was due Feb 6th. He ended up being born Feb 13th at 41weeks.

With this one, I have no clue when we dtd, at all. Months before I kept track of that, but for some odd reason in Feb of this year I didn't track it. My LMP was Jan 29, cycle is anywhere from 29-31 days. According to LMP, the EDD was Nov 4, but I had a dating scan at 9w1d (according to LMP), and baby was measuring top of head to rump 8w4day, which puts my EDD as Nov 8th.

I'm going with Nov 8th because after reading up on it, early dating scans can be pretty accurate +/- 1 week. Of course baby will come when baby is ready.

It all depends on when you ovulated, DTD, how long sperm lived inside you, and how long it took the fertilized egg to travel to uterus and implant itself.