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Dating scan Accuracy?
How accurate are dating scans really? I’ve been driving myself nuts searching the web and I find so many people try to say there dating scan is off by two weeks or more. Makes me worried about my situation. I had a dating scan via ER due to pain in my lower area at 8 weeks measured the baby transvaginally 16.8 mm. My 20 week scan matched up to this date except one day difference. Then I had a 28 week scan due to GD and measured 1 week ahead. People say that later scans the baby has caught up from being behind in the beginning. I don’t understand I am a FTM and I made a horrible mistake sleeping with someone else. Just really wondering how far off the dates can really be? Any help is appreciated.
COMMUNITY LEADER
If you measured a week different at 28 weeks, and that one week is enough to worry you, maybe we should go over your dates.
Speaking generally, early ultrasounds (such as yours at 8 weeks) are the most reliable for determining an estimated conception date. A lot of women who complain that their ultrasound wasn't accurate for dating conception are talking about later ultrasounds. (Babies can grow at different rates.) Most of the time, in the early stages of pregnancy an ultrasound can be a helpful indicator, though not really designed for this purpose.
Diabetes is known to cause babies to grow bigger too. Also, you're further along at 28 weeks than you were at 20. By the time you are at week 40, a careful doctor asked to give an estimated conception date from an ultrasound is likely to say "plus or minus three weeks" or even more. Sometimes young women who later write alarmist posts on the Internet don't hear their doctor, they just hear a date.
If you want, write the dates you had the sex with Mr. Wrong and with your husband, the date of your first ultrasound, and the estimated due date you were given at the 8-week ultrasound and the 20-week ultrasound, and we can see if we can help you with the count and give you some reassurance.
Speaking generally, early ultrasounds (such as yours at 8 weeks) are the most reliable for determining an estimated conception date. A lot of women who complain that their ultrasound wasn't accurate for dating conception are talking about later ultrasounds. (Babies can grow at different rates.) Most of the time, in the early stages of pregnancy an ultrasound can be a helpful indicator, though not really designed for this purpose.
Diabetes is known to cause babies to grow bigger too. Also, you're further along at 28 weeks than you were at 20. By the time you are at week 40, a careful doctor asked to give an estimated conception date from an ultrasound is likely to say "plus or minus three weeks" or even more. Sometimes young women who later write alarmist posts on the Internet don't hear their doctor, they just hear a date.
If you want, write the dates you had the sex with Mr. Wrong and with your husband, the date of your first ultrasound, and the estimated due date you were given at the 8-week ultrasound and the 20-week ultrasound, and we can see if we can help you with the count and give you some reassurance.
6 Comments
Mr. Wrong- May 15 19 only two times for sure 2nd time had a condom but I know that isn’t guaranteed.
Partner (the ones I marked June 8,9,10,12) there’s probably more.
I think I had me streak bleeding June 1st or 2nd but can’t remember the flow scared it was implant bleeding but I have PCOS so never tracked my cycle.
Didn’t take a pregnancy test until July 10 which I went to the ER after and they confirmed I was pregnant with ultrasound but it was abdominal and only 5weeks so said it wasn’t very accurate
Went back at 8 weeks and confirmed Crown rump length as 8weeks1day once again at the ER because of pain and hurting
My OBGYn didn’t do a formal dating scan because of these two scans so I didn’t get another scan until my 20 week anatomy scan
Partner (the ones I marked June 8,9,10,12) there’s probably more.
I think I had me streak bleeding June 1st or 2nd but can’t remember the flow scared it was implant bleeding but I have PCOS so never tracked my cycle.
Didn’t take a pregnancy test until July 10 which I went to the ER after and they confirmed I was pregnant with ultrasound but it was abdominal and only 5weeks so said it wasn’t very accurate
Went back at 8 weeks and confirmed Crown rump length as 8weeks1day once again at the ER because of pain and hurting
My OBGYn didn’t do a formal dating scan because of these two scans so I didn’t get another scan until my 20 week anatomy scan
Menstural**
What due dates were you given at the ER?
(Not "weeks pregnant" figures, but actual dates by the calendar?)
July 10- 3/08
July 26- 3/06
July 26- 3/06
You posted, concerned because a 28th week ultrasound is a week off, but according to your due dates, the sex from May would be four weeks too far back from your projected due date, not just one. Chalk the one-week difference up to the GD, and remember not to freak out if the doctor gives you even more of a size difference from average later in the pregnancy; it might happen if the baby is growing faster than average because of the GD. Your early ultrasounds are the ones that count for dating the pregnancy.
In the meantime, meet with a dietician and get going on controlling your blood sugar for the rest of your pregnancy. That will be much better for the baby and make the birth easier, and it will improve your odds of avoiding diabetes yourself later in life. Women who write in to this community sometimes obsess over paternity when they actually have something more serious to worry about, because paternity is easier to worry about. Don't waste another thought on whether the first guy produced the pregnancy, do spend time working out how to reduce the GD.
Good luck!
In the meantime, meet with a dietician and get going on controlling your blood sugar for the rest of your pregnancy. That will be much better for the baby and make the birth easier, and it will improve your odds of avoiding diabetes yourself later in life. Women who write in to this community sometimes obsess over paternity when they actually have something more serious to worry about, because paternity is easier to worry about. Don't waste another thought on whether the first guy produced the pregnancy, do spend time working out how to reduce the GD.
Good luck!
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