Question regarding EDD

NatureLovers · May 2014

Since I have my first ultrasound on Wednesday, I don't want to be freaked out if my measurements are off and show me to be earlier than I think I am.

So my question is, when they measure the fetus to determine gestational age, do they count the two weeks prior to ovulation that is used in the LMP calculation?

To be more clear, using my LMP, on the day of the ultrasound I'd be 7 wks 6 days. However, if you go by my ovulation date of 4/17, I would be 7 wks even on the u/s date. Assuming all is healthy, would their growth criteria show the baby to 7wks 6 days, or just 7 wks?

I hope that makes sense!

NatureLovers · May 2014

Crap, I just thought of implantation time too. Assuming I implanted 10 days after fertilization, would the baby show to be 6 wks 3 days per LMP, or 5 wks 4 days per ovulation? This is confusing.

kmcorter · May 2014

I BELIEVE you calculate from your ovulation date. so you technically are at 2 weeks when you ovulate and then count from there which would put you at 7 weeks on 5/22. Implantation is calculated into the weeks as part of the gestational age.

Like i said, I think that is how it works. Hope that helps!

liladelphia215 · May 2014

Yes.. they tack on the two weeks.

NatureLovers · May 2014

kmcorter said:
I BELIEVE you calculate from your ovulation date. so you technically are at 2 weeks when you ovulate and then count from there which would put you at 7 weeks on 5/22. Implantation is calculated into the weeks as part of the gestational age.
Like i said, I think that is how it works. Hope that helps!

The issue with that is the overwhelming majority of women don't know when they ovulated.

Milagros315 · May 2014

When they do the ultrasound, they're giving you a number based on the size/maturity of the baby. They can look at a baby and determine that it looks to be about 4 weeks past conception and then they add 2 weeks (using the assumption that women ovulate on day 14) so that baby would have a gestational age of six weeks.

If you ovulated a bit later than day 14, then it is possible that the baby will measure closer to 7 weeks. That's totally fine.

ETA: To be a little more specific, if your baby is growing perfectly on track it probably will measure about five weeks past ovulation/conception which is a gestational age of 7 weeks. Remember, regardless of LMP and ovulation, all babies can grow at slightly different rates so there's that factor too.

kmcorter · May 2014

NatureLovers said:

kmcorter said:
I BELIEVE you calculate from your ovulation date. so you technically are at 2 weeks when you ovulate and then count from there which would put you at 7 weeks on 5/22. Implantation is calculated into the weeks as part of the gestational age.
Like i said, I think that is how it works. Hope that helps!
The issue with that is the overwhelming majority of women don't know when they ovulated.

Very true. I just assumed you were temping since u said u knew your ovulation date.

NatureLovers · May 2014

So basically I should expect the baby to measure at 7 weeks?

[Deleted User] · May 2014

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SpaceGirlSpiff · May 2014

If you're sure of when you ovulated, it should be at 7 weeks, yes.

I'm very similar in dates to you, I ovulated on 04/15 which was CD 16 for me (I temped).... I also have my U/S tomorrow! I *SHOULD* be measuring at 7w1d based on ovulation date

Course .. that month with temping was a LITTLE wonky since I was out of town and had some off days, but I got solid crosshairs on my chart for that day so hopefully I'm right.

Ovulation due date vs. LMP due date is actually only 2 days off though so either way it should be around there.

NatureLovers · May 2014

Sorry, I guess I should clarify what my concern was. I don't really care about the EDD, my concern was thinking the baby should measure nearly 8 wks, but instead it's measuring only 7 wks, leading us to believe that the baby has stopped developing and a m/c is imminent. That's the worry I am wanting to avoid.

MahriM23 · May 2014

I've had 3 kids and I get really annoyed because I ovulate later in my cycle (closer to the 18th day) but the OB never cares and my babies are always super late (by their standards) even when baby3 measured about 5 days smaller than what they calculated based on the first day of my period. they still went with dates over measurements even after I explained when I ovulated. Makes me want to lie about dates this time.

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