Due date by Ovulation or last period?

purplepeanut6 · July 2012

Hi Ladies,

How do you calculate your due date? if I got by O then I am 3 weeks 3 days. if I go by first day of last period I am approx. 5 weeks. I am assuming O is more accurate, but I heard doctors go by date of last period. Just wondering.

Thanks!

Shayliz · July 2012

Most doctors will go by LMP and adjust if necessary after an ultrasound.

MeenaJo · July 2012

I went by my O date because I ovulated ten days late. I'm sure it will change tomorrow after my first U/S. Your doctor will generally go by your LMP but can give you a better EDD if they do a dating ultrasound.

dande2129 · July 2012

The due date from the date of your last period is just an average way of determining your due date if you weren't charting. If you're certain of the day of your O they may go by that, or they may go by the calendar and then adjust based on the first dating u/s. It depends on your doctor, but even my doctor said that most women do not O on cd14.

purplepeanut6 · July 2012

thanks ladies!!

amandamor · July 2012

Your last period seems to be most accurate, I calculated mine myself using the date of my last period and went to an ultrasound today and I was exactly dead on! haha!

Lissa832 · July 2012

Ovulation date is 100% more accurate than LMP. If you are sure when you O based on charting, OPKs, etc, then you should use that date to calculate your pregnancy. Doctors will always start with your LMP to calculate your edd. If you have a dating scan, most will adjust it based off the ultrasound. Others will continue to use your LMP if the edd is within one week of the dating scan edd.

LnR70707 · July 2012

Lissa832:
Ovulation date is 100% more accurate than LMP. If you are sure when you O based on charting, OPKs, etc, then you should use that date to calculate your pregnancy. Doctors will always start with your LMP to calculate your edd. If you have a dating scan, most will adjust it based off the ultrasound. Others will continue to use your LMP if the edd is within one week of the dating scan edd.

This.

NechamaChayim · July 2012

Mine are within 1 day of each other so it doesn't matter much either way. However, I went with the later date.

MrsCarroll.6-10-07 · July 2012

When you go to the doctor you can play the "I don't know" card. That's what I had to do for #2 and #3 because I KNEW that I ovulated later and my LMP and O date would give different due dates.

Really your O date, if you know it, is most accurate. Does your doctor do early u/s?

lenya_35 · July 2012

Ovulation date is most accurate, but if you count starting from your ovulation date, then you have to add 2 weeks. Ovulation date isn't day 1 of pregnancy (well, technically it is, but not according to the whole "pregnancy is 40 weeks long" thing). So on the day you ovulate, you're actually already 2 weeks into your pregnancy. Strange, I know.

sucrets4 · July 2012

Shayliz:
Most doctors will go by LMP and adjust if necessary after an ultrasound.

This.

It's so good to know because with DD I O'd late and would have worried why she was measuring behind. However, the 1st u/s matched exactly when I knew I o'd, so I was fine.

sucrets4 · July 2012

amandamor:
Your last period seems to be most accurate, I calculated mine myself using the date of my last period and went to an ultrasound today and I was exactly dead on! haha!

Yeah, no. Congrats that you o'd on CD14, though! A lot of women don't.

celeste120 · July 2012

my doctors are now going by ultrasound.

GrowingFamily2012 · July 2012

Glad you asked, I didn't O until CD 23. I am figuring that I am only 4 w3d. As you can see, my ticker is going by LMP which the doctor will most likely do and be a week off. Go by O date until you know otherwise.

purplepeanut6 · July 2012

MrsCarroll.6-10-07:
When you go to the doctor you can play the "I don't know" card. That's what I had to do for #2 and #3 because I KNEW that I ovulated later and my LMP and O date would give different due dates.
Really your O date, if you know it, is most accurate. Does your doctor do early u/s?

Not sure going to call tomorrow to scheduale an appt

purplepeanut6 · July 2012

GrowingFamily2012:
Glad you asked, I didn't O until CD 23. I am figuring that I am only 4 w3d. As you can see, my ticker is going by LMP which the doctor will most likely do and be a week off. Go by O date until you know otherwise.

Right, So I Od CD29. (I have really long cycles) So...

LMP DD is March 18

O DD is April 1

Isn't that a huge difference?

nallsl · July 2012

I had to wait for an u/s because I hadn't had a period in months.

mandamerlot · July 2012

I tried explaining this to my doctor, but he opted to still go with my LMP which was May 13. I know 100% that I ovulated on June 1st (I have mittelschmerz on my right side, so I can feel myself ovulate- pretty handy!). I didn't get an early ultrasound & now I'm worried that when I go in for my ISP (what the screening ultrasound is called in Canada), that is supposed to be done between 11weeks and 15 weeks, I won't be as far along as expected & it won't be an accurate test. For my ticker on here, I am using my EDD, but the app on my phone I keep swapping between OD and EDD.

dande2129 · July 2012

purplepeanut6:
GrowingFamily2012:
Glad you asked, I didn't O until CD 23. I am figuring that I am only 4 w3d. As you can see, my ticker is going by LMP which the doctor will most likely do and be a week off. Go by O date until you know otherwise.
Right, So I Od CD29. (I have really long cycles) So...
LMP DD is March 18
O DD is April 1
Isn't that a huge difference?

Oh yeah, that's a pretty significant difference, especially if you're "over due" but you really aren't. I had a similar situation with my first. I KNEW there was only one possible day that I could have gotten pregnant that entire month. The doctor I went to at first was a douche and wouldn't adjust my due date. I was supposed to be due May 8th, but they gave me a due date of May 23rd. Once she started talking about a c/s because I had a "big baby" around 31 weeks, I fired her, got a second opinion with another u/s and confirmed the due date of May 8th.

Baby was born May 7th and absolutely perfect.

EIsieMae · July 2012

My OB would go by LMP until after the first ultrasound. If the ultrasound showed a difference of 5 days or more then she would adjust one way or the other.

mom2b22013 · July 2012

My OB went by LMP even though I know the date I Oed. Oed date would be Feb 6, LMP would be the 10th based on US I think they have it in my charts at Feb 8. Too many dates

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