Thursday, February 10, 2011

Due Date By Numbers or Pictures?

When I got pregnant with this baby, the doctor, as always, asked about the dates of my cycle to estimate a due date. Don't they always?

Then, when I had an ultrasound, the measurements of the sonogram gives its own estimated due date. In my case, my sonograms put my due date about a week later than my cycle would have.

My doctors seem adamant about using the sonogram date. I'm a little confused as to why since I've always understood sonograms to have a small range of possible error, thus making their date no more certain than mine, and at least I had specifics concerning mine.

My biggest complaint about their insistence of using the later date is that every time I use the earlier date, they suggest I don't really know when I conceived or even when my last cycle was. This really has come to irritate me. First of all, if I didn't know, why did you ask me? Secondly, when I provided a chart showing all the relevant information, it wasn't based on whims. If they really want to use the sonogram date, fine, but don't do so under the false pretense that I don't know what I'm talking about. (Ironically, if they did the math, using the later sonogram due date, I would have had to have gotten a positive home pregnancy test only 9 days after conception. ... not too likely.)

Now, of course, any due date is only an estimate and only worth so much. I find this especially true as I've never made it to any of my due dates anyway. But where this disagreement about dates is causing difficulty is in setting up appointments until then. Certain tests are supposed to be done on or by certain weeks. This has caused a bit of confusion when I think I can have the test by Date A and they insist by Date B. Of course, a test is a test, and if it makes them happy, Date B is fine, but I've had to reschedule a couple of appointments now due to the confusion. My other concern on the issue is that, as I tend to deliver early, what might be full term but early by my date, might not full term by their date. By their estimation, my next appointment is at 35 weeks, by mine, it is 36 weeks.

So what date do you go by? Have you ever had such confusion over your due date?

P.S. - Exactly when this baby arrives has become even more interesting to me based on it's relation to the two due dates. The fact that this baby is already in position and dropped so early has not escaped my attention either. James thinks this baby will be born by the Annunciation or even by his birthday the previous week. Any earlier than his birthday, and my doctors might not be so pleased with their choice of due date, though it would be fine by mine. :)


  1. I use the sonogram. Because in my case, it's always right. I have a 31 day cycle and the EDD based on my cycle is always based on a 28 day cycle. My doctors always go by the EDD based on dates. The last two pregnancies I was able to give an exact date of conception which matched identically to the sonogram dates (which are based on measurement). Typically the sonogram's margin of error is greatest the later you are in your pregnancy. It is easier to get better measurements when the baby is smaller and less active which is part of it. The dates, the sonogram are all just tools. Not exact science. In my case, it doesn't matter terribly because I will never carry to term as I have to have c-sections and they have to be at 38 weeks to avoid my going into labor. If that is really 37 weeks...I still have a full term baby.

  2. With my last baby, I had the doctor move my due date up a week. I felt it was wrong, based on my charting. My first born came two weeks early, and if this one followed suit, along with being ANOTHER week off based on the ultrasound, I wouldn't have been able to have a homebirth as I'd planned.

    She came right on the new date, exactly when I predicted she was due! She was 8 lbs 6 oz, too, which leads me to believe she was completely full term.

    With this current pregnancy, the ultrasound differs from my calculations by only three days, which is small enough not to be a worry.

  3. Hmmm. By cycle do you mean they are calculating by date of last period or are you charting fertility signs?

    I've always been annoyed at the doctors' refusal to seriously consider that my charting yields a much more accurate date than the beginning of my last menstrual cycle. See, I want to shout, I know the *actual day* of ovulation so there doesn't have to be any guesswork at all based on average length of cycle. We know for certain within 24 hours of when the baby was conceived.

    Fortunately the discrepancy has always resulted in them putting their estimated due date after my calculated date. If they were moving it to be earlier, I'd be annoyed and more inclined to fight with them over it. Especially as they want to deliver at 39 weeks at the latest so I don't go into labor before the scheduled surgery.

    For the record, with the first two kids both times my water broke and I went into labor it was several days after my calculated due date.

  4. Well, I guess I should have been more specific when it comes to "cycle". In my case, I know, within 2 days, of when this baby was conceived, and that is 5-7 days before the sonogram due date would say so. I just find it frustrating they won't listen to me on this, but at least I'm not the only one.

    Melanie, if they don't listen to you, at least the direction they move it works to your advantage. My first was 3 days early, my second 11 days early and my third 7 days early. Theoretically, given when I've gone into labor and given birth, I should be full term by either due date, but as I always go early, I just don't want any concerns over being pre-term by their date but full-term by mine. The fact that this baby dropped on New Years Eve (exceptionally early for me) likewise makes me think this baby will be early.

    Tienne, glad to hear it isn't causing complications this time around and glad to hear you were right.

    Kristen, I can see where having a longer than 28 day cycle would effect things but at least your sonogram date matched up with your ovulation date. I had a supervised student technician do my sonogram. She struggled a bit. In fact I was on that table for an hour and 15 minutes. I got to see a lot of my baby :) but was fairly sore for a couple days afterwards having someone press on my abdomen that long :(. So maybe my sonogram was accurate, or maybe not quite as accurate as it could have been. :)

    I wonder to what extent requiring a c-section makes more or less of a difference in due date discrepancies?