Estimating Gestational Age

[Anonymous]

How "accurate" are obgyn's estimates of age? I had my first prenatal appt yesterday and the doctor did the uterine palpitations and said "yes, this feels like the size of a 7-8wk pregnant uterus". We went in to the appt believing we were 7-1/2wks pregnant. But then he sent me for the initial ultrasound. The cool part is that we saw the baby's heartbeat. But, the sonographer and the ogbyn who did the test said the embryo was measuring as if it were just a day or two over 6wks.

This seems to be a pretty big deviation, and set back my EDD by about 10 days. Is this kind of discrepancy common? Is it a reason for worry? thanks.

[Anonymous]

It's maddening, but normal I think. The same thing happened to me. Period math put me at 7.5 weeks, but early sono put me at 6 weeks and 3 days. I'm now 33 weeks and they tell me that he's measuring large. Go figure.

Anyway, he's totally healthy. Good luck to you!

[Anonymous]

There is no reason to worry. The first estimate that the doctor gives is just an estimate based on when you COULD have ovulated. The sonogram gives the accurate estimated due date based on the babies actual size. My doctor's first estimate was off by about 4-5 days from the first sonogram estimate (which has been backed up by subsequent sonograms). You have seen the heartbeat - that is a great sign. Congratulations.

[Anonymous]

My early sono estimations were almost a week ahead. I am sure of when I got pregnant, I'm a lesbian and there was a lot of planning and tracking for the one insemination that was done. The doc was suggesting the due date, but I reminded her of the circumstances and she left it as it was.

Unless you are sure of when you ovulated, it is hard to be sure of when you actually got pregnant. Ovulation can vary from cycle to cycle.

[Anonymous]

...was suggesting changing the due date....

[Anonymous]

Thanks all for your reassuring feedback. I'm 35 and my husband is 51 and this is our first together (he has a son from a previous marriage), so obviously we're concerned about any indications of problems. And, I got pregnant basically immediately after I stopped birth control so we have no way of knowing how long my cycle is/was. 32 days after my last period I had a positive pregnancy test, so that's the best we can do in terms of narrowing down when ovulation occurred.

I appreciate knowing this isn't abnormal!

[Anonymous]

With my first, they reset my EDD after the sono revealed an 9 day difference (behind) the date determined by my period. Guess what, the baby measured large for gestational age after the second trimester and I went into labor a week early. This time around, the sono revealed an 11 day difference with the date determined from my period. I knew there would be a lag since I know for a fact that I ovulate late. Personally, I prefer when they set the official EDD back a week- I feel like it gives your body more time to prepare for labor without threats of induction. Good luck and enjoy your pregnancy!