Gestation age?

[Katiekay8998]

Ok so my LMP was October 21st but at my ultrasound they dated me at October 26th for GA. What does that mean? Does that mean I conceived on October 26th? Or 2 weeks after? I am confused as to why my GA would change if my LMP was deff October 21st?

It would mean you conceived approx 14 days after October 26th. Do you have 28 day cycles or more like 33 day cycles? Could be that you ovulated a few day’s later if you typically have longer cycles.

I just don’t get why my gestation age would change if I definitely know when my last period happened? Is that normal?

It's very normal for your dates to change at the dating scan.

I had my scan today. lmp put me 12+3, scan put me at 13wk. All is looking well and that's the important thing.

Yes, gestational age is calculated based on last period but in reality it only works if you have a typical 28 day cycle and ovulate on day 14. Your ovulation date is what is important, some women don’t ovulate till like day 21, so their gestational age would actually be a week after their period started.
Even so, scans do have a margin of error which I think is 3-5 days.

Okay so if my gestation age turned to 10/26 instead of 10/21 that means I probably ovulated 14 days after 10/26?

It could've been later ovulation or later implantation. The LMP calculation is a guide based on textbook cycles, the scan will be more accurate.

Yes correct, it would mean you likely ovulated 14 days after 26/10. However as I said the scans can have a few days error, and 5 day’s is a pretty small amount. As you are 16ish weeks, baby can be a little big of a little small. Is this the first scan you had for this pregnancy? I had fertility treatment so I know my exact day of ovulation and early on in pregnancy I was measuring 5 day’s behind and now I’m almost 14 weeks I’m measuring 3 day’s ahead so that’s an 8 day window.

It means you likely ovulated late as they use LMP as a rough guide which is usually based on a 28 day cycle as a rough guide

I had ivf and my dates still changed by a week earlier...

Gestational age can vary loads once you’ve had your scan. The standard would be based off a 28 day cycle, ovulating on day 14, however that isn’t the case for many women. Your GA at ultrasound is based off baby’s size. My due date based off lmp is 1/6/21 but my given due date after my scan is now 27/5/21

@Nat4392

Gestational age can vary loads once you’ve had your scan. The standard would be based off a 28 day cycle, ovulating on day 14, however that isn’t the case for many women. Your GA at ultrasound is based off baby’s size. My due date based off lmp is 1/6/21 but my given due date after my scan is now 27/5/21

so i got pregnant from sex in nov not oct?

You would've become pregnant from sex in November based on either of the dates you mentioned.

Both of these ways of measuring the dates are just estimates that help the professionals looking after you plan your care based on when they think your baby will be born. But in reality I think it's only 5% of babies that are born on their due date. The scan date is generally seen to be a more reliable predictor of when the baby will be born than LMP which is why they adjust the dates after your scan. In reality you'll never know exactly what day you conceived (unless you only had sex once that cycle or had IVF or something like that) because there are so many factors that can affect it by a couple of days: late/early ovulation, fast/slow implantation, scan measurement inaccuracy, natural variation in size of babies... just one of life's unknowns!

@Katiekay8998 yes November you would have conceived. Is there a reason you’re worried about differing dates? Is there a question over paternity etc?

[quote Nat4392]@Katiekay8998 yes November you would have conceived. Is there a reason you’re worried about differing dates? Is there a question over paternity etc?[/quote]
yes. one man was in october another was in nov. Even doctors wont give 100% certainty.

It does all depends on the dates in October and November really. As any day after your period could theoretically be the father.

If the first man was before your period in October then it’s not him... if he was after your period then it could be.
When was the man in November and when did you get a positive pregnancy test?

@BabyC21

If the first man was before your period in October then it’s not him... if he was after your period then it could be. When was the man in November and when did you get a positive pregnancy test?

the guy in october was like the day before my period (my actual period was oct 21) but according to the ultrasound my GA was Oct 26th. The man in novemeber was like all different dates in Nov. I got a positive pregnancy test on nov 24 and then the next day had a blood test to confirm with an hcg of 170

@BabyC21

If the first man was before your period in October then it’s not him... if he was after your period then it could be. When was the man in November and when did you get a positive pregnancy test?

he was before my period but i took plan b and my obgyn said plan b doesnt make an actual period happen its like just a bleed so idk if it was my period but i didnt get a positive till almost a month later and my hcg was 170 36 days after intercourse with man # 1

@Katiekay8998 it is definitely the November guy. Going off either lmp date, you would have conceived approx 4-9 November

Yeah I agree it’s definitely November guy. 170 HCG is about 4 weeks pregnant (2 weeks after conception) so couldn’t be October guy. Also you would have passed your fertile period with October guy if it was the day before your period.

@BabyC21

Yeah I agree it’s definitely November guy. 170 HCG is about 4 weeks pregnant (2 weeks after conception) so couldn’t be October guy. Also you would have passed your fertile period with October guy if it was the day before your period.

I just don't understand why my obgyn wont tell me with absolute certainty because it is literally killing me. I think i got my period a little earlier than usually because i took plan b so i think i could have been ovulating but not sure.