Accuracy of Conception Date

If you conceived 6 weeks earlier than all the sonos have said...then there is something wrong with the baby.
There is the chance they could be off by about a week because
not all women are 28 day cycles. But not 6 weeks. And 3 sonos have all said that.

Ok so I would be the one that has not been the norm. Because of isses getting and staying pregnat I start having ultrasounds that day I find out. With my first the child they were off 2 1/2 weeks. My second they were right on the money and with my 3rd The ultasound was 2 weeks off. However it is unlikely that the sono would be off by 6 1/2 weeks.

The gestational period for pregnancy isn't exactly 9 months, it's actually 40 weeks. It's really a math thing. My doctor set my due date at 9-11 using his little wheel thing. We counted backward 40 weeks and it put our conception date when I was working a 72 hour shift. Didn't happen then! We looked at our calendar and knew beyond a shaddow of a doubt that our conception date was 12-15, counted forward 40 weeks to 9-7. He was two weeks early on 8-24 (induced due to pre-eclampsia). So if you think you conceived around 7-8, count forward 40 weeks and count on your new arrival around that time. The sonograms are most likly accurate but better to be prepared!

Hi K.,

The whole conception and due date thing is quite confusing. In short answer, I'd say no, it is not likely. Possible? maybe, but you would be much further along.

They kept telling me that I was due 12/29, but I knew better. I knew it was much later. Sure enough he was born 1/2 by induction. If we had let nature take its course it probably would have been one more week.

Every woman is different and since most of the time, we aren't paying attention, we can't really tell when the conception date is. It is all based on average and al calculations are estimated.

The first 4 weeks are considered your last menstrual period and then conception. (hence the word cycle)

After your period (week1) you ovulate around week 2. That is 14 days after the first day of your period. (this is based on the average 28 day cycle) They assume you had sex around that time and conceived. Now weeks 3 & 4 is conception. Therefore your baby is actually 2 weeks "younger" than they say. Which makes pregnancy really 38 weeks instead of 40.

My cycle is alot longer. That's how I knew I didn't conceive when they said I did. I wouldn't have been ovulating at that time.

It's confusing, but once you get it it all makes sense! :) I hope it helps!

That's a whole months difference. Sono's are known for being wrong about many things. But if you had a sono at 5 weeks that would be your most accurate. The earlier the more accurate. If your truly concerned that you concieved that much earlier than consult your midwife or doc. Always listen to your gut and follow your instincts.

I am sure they accurate because during sonogram, they measure the fetus and are able to determine by that how many weeks and days it is. Correct me moms, if I am wrong. I'm an IVF'er so never had to guess on the conception dates...

-Char

I actually just asked my OB this, and she said that the earlier the ultrasound the more acurate the EDD. No matter how big or small your baby will be, in the beginning, growth happens in a very specific time frame. The later the ultrasound, the less acurate, because then it is just about the babies size, as they have developed all of the organs etc, and are just getting bigger. It is similar to estimating the babies weight through ultrasound, they can be wrong by more than a pound. So, try getting an ultrasound ASAP, and that, along with your last period, should help out alot! Good luck!! ~A.~

Hi K.,

If it helps you at all... I'm 30-31 weeks pregnant with twins and we did IUI and it was done sometime in early August (Not sure of the actual date), but I can tell you that if you're 30 weeks now... you'd be closer to full-term if you conceived July 8. We found out we were pregnant toward the end of August (around the 20th) and it was 2 weeks after the IUI was done.

Might just give you a "marker" to help you figure things out. But it sounds to me like your doctors are right with your conception date.

Best of luck to you and your new baby!
K.

I think Char is right, the sonogram measurments give the best indicator of the approximate time of conception. With both of my pregnancies, the actual due date was determined to be 40 weeks from the first day of my last period so I guess that gives a pretty close estimation as well.

K.,

Mine was right on, but I knew the date I got prenant. I was due on September 1st (Date never changed) and my son was born on August 21st.

They are usually quite correct in regards to dates n such so I would not doubt it too much.

I'd say they're within 2 weeks

K.-
I worked in OB/Gyn high risk ultrasound for 10 years. The earliest ultrasound is the best for dating purposes, but that will not give u an exact date of conception within two weeks.

Like everyone else is saying, if your EDD is May 14th then there is no way that you conceived July 8th. If you had, then you would be having your baby in early April.

i'd say within 1 week

I.

If you are basing the accuracy on the little chart wheel they use, these can be off by about a week or a little more. The reason for this is that it is based on a menstrual cycle of 28 days. There are many woman that this does not apply to.

If it is based on the sonogram, the conception date may be off by a few days in the beginning, but as the pregnancy progresses, the sonogram measurements become more accurate.

I hope this helps!
Jodi

I'm a labor and delivery nurse. Sono's (especially early ones) are quite accurate when determining your due date. Since all of your other sono's have been consistent with that date, you can be fairly sure that it is correct. July 8th and August 21st is quite a difference. It would be almost impossible to be off by that much when they determined your due date. Hope this helps.

When I was pregnant with my first I had the same kinda thing. I thought my due date should be January 10 and the Dr was telling me January 30. What do you know I had my daughter on January 9. My daughter was 5 lbs 13 ozs. The reason everything was off was becasue the give you the due date by the first day of your last period and the size of the baby. Since my baby was so small she was not showing to be as far along. Don't be shocked if you baby comes sooner to what you think the due date is then what the Dr tells you.

K.,

I have a 9 month old daughter, and her original due date was May 15th. I had asked my OB when my conception date was, because I was curious, and it was between August 21st and August 23rd. Maybe that can give you something to judge by. Hope it helps.

Take care
T.

I would say that there's no way you conceived in early July if your due date is mid-May. If you had conceived in July, your due date would be in early April- which would mean they were off by over a month! Unless you're baby is measuring REALLY big- I'd say that they're probably pretty close....

If all the sonograms say the same thing, then there is almost no chance that you concieved on July 8th. If that was the case, then there would be something wrong with the lack of growth of the baby (not likely). You can rest assured that the Dr. is right! :-) Good luck!

I would say the date is very accurate. I believe all fetuses hit the same development milestones the first 12 weeks or so. After that, they grown at their own individualized rates. So that first sonongram is probably right on target.

I always took the first date of my last period, subtracted 3 months, and added 7 days to get my due date. It was almost perfect (even by sonogram dating) with each of my 4 pregnancies.

My dr. said the same thing that Amber's said. The earliest sono is the best indicator. I pretty much knew the date of ovulation on both pregnancies and both sonos were right on track.