Due Date Question

[SoonToBeMommy317]

Hi all...
I'm new here.
And this is my first pregnancy so I'm just doing my best to get through it.
But I do have one serious question and need some help...



When doctors calculate the due date, don't they do it using a supposed 28 day cycle?

If my cycle was 36 days instead of 28, is it possible that the estimated due date they have given me is incorrect by a couple weeks? I calculated it on a website, and it said I should be furthur along than the doctor says.


Additional details:
If any of you know how to calculate, here are the additional details...maybe you can hep me out a bit and make sure I did this correctly.

I'm not exactly sure of the last date I had my period but I know I took the test on March 9, 2009. I had already missed my period by then. So, just a round-about guess, let's say I missed my period on March 7, which is somewhere around the correct time (matter of days). That would mean my last know period was around January 31st, 2009. With a 36 day cycle...what week should I be at right now??
Thank You for the help ahead of time!

Another bit of info: MY calculated date said I was around 35 weeks. The doctor says 32.

However, my last visit (last tuesday) He actually had to double check the due date with my first ultrasound (I was 13 weeks already) b/c he started to think that maybe it was incorrect because of the baby's size. (He was shocked...said either the due date was inaccurate or i'm having a really big baby!) He was "unsure"....go figure. So I still don't have a clue what week I'm in.


Can someone help me figure this mess out please?

I don't know if i'm correct about being further along, or if i'm just ready to have my daughter now.

[hazleyez]

all the ladies have great answers and yes it goes by your last period.. so if you have had the u/s early like 6-10 weeks i believe then that would be the more accurate due date. Good Luck.

[jenstam]

If you had a 36 day cycle you would be less farther along than they have calculated for you using a 28 day cycle, not more. But, it is standard to use a 28 day cycle. I would just go with what they have for you as a due date. In the end a few days doesn't make much difference, give or take.

[Jonezy16]

Hi there,

I'm also going to say that you should go by the date of your last period.  Mine was not far away from yours (Feb 3rd) and I'm 32 weeks and 2 days, so my guess is your 32 weeks!  Although my lil' boy seems to be growing very fast, he is already 5.7 pounds.

I'm still mixed up with the whole concept of 36 weeks - a 9 month pregnancy - as opposed to 38 - 40 weeks being considered full term??

Anyhow, take care!  

[bny807]

Usually the later you get a sono in the pregnancy (especially 20 weeks and up) the more inaccurate dating gets via ultrasound, since "Normal" size can vary so much, so usually the first sono you get is the most accurate as far as dates go. .. yup i think they do calculate it also based on last mentral period being in a 28 day cycle..so if you told them your date of your last period- they typically assume you ovulate at around 14 days or so.. if your cycle is 36 days.. you probably dont ovulate till day 22 or so so that could put your actual pregnancy age a week younger than they are predicting..... i am supposed to be 34 weeks, but have been measuring 3 weeks ahead for months now.. but we are still going with the 34 week estimate since that dates from my first sono.. GOOD LUCK and congrats on your pregnancy!