How accurate are ultrasound due dates?

[Ninjasurprise]

Today I went for my first scan and I was given 9 weeks pregnant and the baby's size is 2cm and a heart rate of 176pm  I last saw my boyfriend 7 weeks ago this is all confusing for me and was embarrassed to ask about the time difference, while having my scan:/  Any help would be appreciated!!

[AnnieBrooke]

If your boyfriend goes with you to an appointment, ask the doctor to explain to him the difference between gestational age (the weeks & days count) and timing the pregnancy from conception.  Otherwise you might have a worried or suspicious boyfriend on your hands for no reason.

[Ninjasurprise]

Thank you! I'm glad others understand all this. Very confusing for a first timer, you advice is very much appreciated

[Ninjasurprise]

Thank you for your help! The information is a massive relief

[AnnieBrooke]

All medical counts of pregnancy (the number like 6 weeks 3 days or 9 weeks 0 days) begin on the first day of the last period you had before getting pregnant.  If a doctor says to a woman, "Congratulations, you are 8 weeks pregnant!" he means 8 weeks since her last period began, or about 6 weeks since conception.

The count is done this way because the period is a big, obvious signal, not because the doctor thinks you are pregnant when you are on day 1 of your cycle.  That's why pregnancy, which takes 38 weeks, is counted as being 40 weeks long.  They add a spare two weeks at the front to calibrate to the medical convention of beginning the count on the presumed first day of the last period.

[sousou123455]

They date from lmp so really when the say your 9 weeks from lmp your really 7 weeks from the time you concieved.

So it fits the timeline.