QuestionI am having a problem with my current ob/gyn and the due date she has been giving me. My LMP was 7/2/06 and I was trying to get pregnant and remember that my husband and I were intimate on 7/13, 7/14, 7/15, and 7/16. I also know that we were not intimate in the month of August at all and I know that sounds weird, but I started working a 40 hour job on 7/25 and another job on 8/1 which put me up to working 70 hours a week minimum. Anyway I was working a full time second shift job and a full time third shift job both places open 7 days a week, so being intimate was out of the question. To get to the point I had an ultrasound at the end of October and they dated me at being only 10 weeks and I should have been 16 weeks. Then I had another ultrasound in the middle of December which still kept my due date the same as the 10 week ultrasound....then again I had another ultrasound at the end of January which measured the baby at being in the 50th percentile for that due date which by the way is May 20th (not April 8th like it would be if they were going by my LMP only)so he was measuring a little small at that point but then at my next two appointments my fundal height was measuring 4cm larger than it should have been so then I was sent in for another ultrasound at the end of February and this time the baby really was measuring 4 weeks larger than the May 20th due date and he was also measuring in the 80th percentile for his weight. My problem is really kinda big see, my periods have been irregular for the last couple of years (I should say I was only having my period 2 times a year)so it's obvious that my ovulation could very well be off track. Also this is my third child and with my first two my periods were regular and the dating always matched up so I never had this problem, but I never go into labor on my own so being unaware of my due date is bad for scheduling a c-section. Anyhow they say that my first three ultrasounds confirm the May 20th due date and the earlier the ultrasound the more accurate the calculations are...so they are keeping my due date as that for now even though the newest one says I am farther along than that. So basically my questions are is it true that my earlier ultrasound due dates are right?, Since I am measuring so much bigger now then does that mean that the baby will be really big? (by the way my gestational diabetes test came back fine I thought I should add that because I know that can cause a person to have a big baby)Is there anyway that I am right and they are wrong?, also my ob said she was going to send me in for another ultrasound in about 4 weeks to see how much bigger he is I am just wondering if she has no intention of changing my due date then why continue to get more ultrasounds...I realize that you probably can't answer that last question because you don't know what her reasons for continuing to check his size are, but maybe you might know why she would continue to check. I mean I would understand if I was going to deliver vaginally but since I am not then why does it matter how big he's getting? Sorry about the rambling I just wanted to make sure that I got everything out.
AnswerDear Katie,
OK - first off - your doctor is exactly correct in that the earlier ultrasounds are nearly ALWAYS the most reliable for dating purposes. As the pregnancy progresses, different factors can alter the baby's growth and development. In the latter part of pregnancy the measurements will be affected by growth variations and will no longer reflect the fetal 'age' as accurately.
It is important to remember, especially with your irregular cycles, that the estimated due date isn't calculated by conception date. Meaning this... with a 5/20 due date, your estimated conception date would actually have been the end of August and could actually have even been the first day or two of September.
As far as your doctor wanting another ultrasound, it sounds like she is simply trying to be as thorough as possible - probably because there is a bit of a question about the dating due to your irregular cycles prior to the pregnancy.
Believe me, if the dates are off by that much and you are actually right that you would have conceived mid-July, your baby will want out mid-April. There won't be a question about it. Yet another reason why your doctor probably wants another ultrasound in 4 weeks!
I hope this information has helped you and answered your question. I wish you well.
Brenda
