First Trimester / Dating Ultrasound

※ Download: Accuracy of dating scan at 6 weeks

By 8 weeks gestation the baby and its heart beat can be detected relatively easily with trans-abdominal and trans-vaginal examination. The size and appearance of this sac will be assessed. Obstetric ultrasound has played a significant role in the development of diagnostic ultrasound technology in general.

It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. Why do I need a dating and viability ultrasound scan? It is also impossible to do a thorough foetal screening assessment because it is still just too premature in terms of embryonic development. She will be able to identify where the sac has implanted in your uterus to rule out an ectopic pregnancy.

6 weeks pregnant - It involves scanning with the ultrasound probe lying in the vagina.

I've split this question out from an earlier thread... I've just been for my 12 week scan and they have told me I am 15 weeks pregnant. This simply does not work out - I am sure of my dates and even did an ovulation test to check when I could conceive that month. They must base the measurements on averages, but 3 weeks out seems like a lot. Has this happened to anyone else? If so, did your dating scan turn out to be right according to later scans? Or might they tell me later on that my dates were correct after all. Can some babies just grow faster than others? Thanks Yes I am measuring it correctly - I was a bit obsessed and recorded everything in my diary. They said that my last 'period' might have just been spotting but I'm sure it wasn't. Everything ties in with my dates first day of last period, date of ovulation test, date of getting jiggy! I am simply baffled that the scan shows the baby to be 3 weeks bigger than it should be. I'm in a similar position.. I was scanned at what I thought was 8 weeks 4 days.. I just hope baby is developing okay. By my dates I was 7 weeks, by theirs I was 6 weeks. The sonographers explained that the earlier the scan the more accurate as the embryo has very standard development. I had one embryo with fetal pole and heartbeat and one blighted ovum. The sonographer explained that indicated that this was a twin pregnancy with only one twin viable and could explain the date confusion as I may have ovulated twice in one cycle. So it sounds like the scans are pretty accurate then. I did tell the Dr about the positive ovulation test and he didn't tell me that it could have been the pregnancy hormones, but that sounds like the most likely explanation. I then went for another scan on the 22nd Feb and got told I was 9 weeks 1 day. I slept with someone on the 21st December and have spoken to my doctor about this and she says sperm can only live up to 3 till 5 days so the time frame misses it as I would of fell pregnant beginning of Jan. They assume ovulation happens 14 days after your period, so going by lmp dates you would be 13+5. From ovulation would be 11+3. I would expect a 13 week fetus to be significantly bigger than an 11 week one. This is all while using ovulation tests.

How accurate is a due date that is determined by ultrasound?
I did tell the Dr about the positive ovulation test and he didn't tell me that it could have been the pregnancy hormones, but that sounds like the most likely explanation. The nuchal translucency measurement can be taken during the dating scan. I would expect a 13 week fetus to be significantly bigger than an 11 week one. The yolk sac is attached to the embryo and contains nutrients to feed it while it is developing. I was told between 4-5!