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  • Dec. 20, 2008

    What does 'due date' mean?

    By Mary Murry, R.N., C.N.M.

18 comments posted

Do you have a due date and wonder just what it means? It's a good question.

A due date is arrived at in one or more ways. The most common way is to take the first day of your last menstrual period, subtract 3 months and add 7 days. Then there is the gestational wheel where one arrow is put on the first day of your last menstrual period and the other arrow points to your due date.

You can use the due date calculator in the links below, put in your first day of your last period and get a due date. Now you have one date. Then you see your health care provider and do an ultrasound. Say it looks like the baby is a week bigger. Now what? Does that change your due date? It all depends on when the ultrasound was done.

There are specific times when ultrasound is very accurate for dating and other times when it is not as useful. I have known women who have been told they have 3 or 4 different due dates. It can get very confusing. Any due date is plus or minus two weeks. So you can have your baby anywhere from 2 weeks before your due date to 2 weeks after your due date and be pretty much on time.

It is very hard not to focus on the wonderful date you have been given. That is the day you get your body back. That is the day you become a mom, whether for the first time or the last time. That is the day you expect to see your feet again. The odds are not in your favor that you will deliver on that day. About 40 percent of women have their babies before their due date, about 46 percent of women have their babies after their due dates and only 4 percent have them on their due date.

I have no special words of wisdom for you about the due date. You won't stay pregnant forever. The baby will come when it is supposed to. This is another one of those lessons in control pregnancy teaches us.

If you have some thoughts or experiences to share about due dates, please do! Thanks.

18 comments posted

blog index

  • October 15, 2009 6:36 a.m.

    Please if some there can help me quickly, I got marriage, and I am looking to get pregnant I go through your information but nothing happen this month I have my LMP on 28 Sep,2009, I and my husband play sex everday once for a while, up to now nothing had happen, can any one help me with my due date.

    - christine

  • April 15, 2009 11:34 p.m.

    I've actually had 2 of my 3 babies on their due dates. There was no induction or c-sect, they just decided to be perfectly on time. I wonder what the odds of that are.

    - Jamie

  • April 15, 2009 9:25 p.m.

    Today I went for an ultrasound due to sever cramps... all is well! Got to see the little bugger! Little heart pumpin' away! However, the tech said that the baby was measurring at 6 weeks 1 day.... that math doesn't seem possible to me. I calculate 7 weeks. I had my last period on Feb 25th.....used an ovulation kit and had a LH surge on march 10th(ovulation). Positive preg test on March 19th....way before my next period was due....if I was only 6w1d I shouldn't have had a positive test for another week...right??? So confused! Is it possible the baby is just small???

    - Robin

  • April 4, 2009 7:36 p.m.

    My advice to any pregnant woman would be to not have any expecations about your due date. I always thought that by my due date I'd be done with this pregnancy and have my baby. The reality is, I'm 2 days (feels more like 2 weeks) overdue and have NO control over when this baby decides to get here. My unrealisitic expectations are making being overdue that much harder for me. Prepare yourself for the possibility of being overdue.

    - Michelle

  • March 11, 2009 10:18 a.m.

    Please i really want to know,i did my periods last month on the 9th,this month its 11th and i have not seen,my periods?does that mean i maybe pregnant?

    - Irene

  • March 11, 2009 10:14 a.m.

    Please i really want to know,i did my periods last month on the 9th,this month its 11th and i have not seen,my periods?does that mean i maybe pregnant?

    - Irene

  • February 23, 2009 12:15 p.m.

    i know this really doesnt matter i just had to say it when i was pergant my baby was do 3 days after my birthday

    - lashanal

  • February 19, 2009 1:47 p.m.

    I remember reading years ago when I was pregnant that the closer conception is to ovulation the greater the chance of having a boy, because Y sperm swim faster but X sperm live longer, thus conception a few days before or after ovulation is more likely to produce a girl. True?

    - Raquel

  • February 11, 2009 1:35 p.m.

    If I know the date I conceived because I'm charting and know when I ovulated and when my temperature rose the day after my peak day, then how do I calculate an accurate due date?

    - Rebecca

  • January 21, 2009 10:54 p.m.

    I am so glad to see that you state that 42 weeks is absolutely normal and some women go even beyond that. It's so sad that Dr's today do not see that as normal and will induce much too early. I have gone 11 days late with both pregnancies and was under so much stress as a neared the 42 week mark the first time. We need to regard the "due date" as the estimate that it is. Every woman is different. Thanks for putting this info out there.

    - boing boing

  • January 14, 2009 8:11 a.m.

    I'm 77 and back in 1954 the due date of my first child was June 18th - he didn't arrive until July 15th - there were no ultrasounds, induced labor, etc at that time- you just waited. One person told me that I would deliver on the next full moon, and sure enough that's when my son arrived at 9lb 10 oz. An "old wives tale" with some truth - when I entered the maternity ward they were preparing for a "rush" which they said occurs on the "full moon" (also more boys are born at that time) I have to say that I had very irregular periods prior to my first child.

    - Ellie

  • January 13, 2009 6:03 a.m.

    My LMP is 14.09.2008 and accordingly Im 17 weeks 5days but the USG shows im only 13 weeks and 3days.my periods is irregular.so how do i calculate my due date?should i follow my LMP or the USG report?I'm so confused..

    - naz

  • January 9, 2009 9:52 p.m.

    Is there a place to see a graph of probabilities per-day relative to due date? I've searched online but haven't found anything.

    - Ted Carnahan

  • January 5, 2009 10:15 a.m.

    I have heard you are more likely to exceed your due date - deliver late - in your first pregnancy. Is that true?

    - Alison

  • December 29, 2008 1:44 p.m.

    I am sorry for the confusion. Your math is correct, I have left out 10%. That 10% includes those who miscarry and those who carry their pregnancy longer than 42 weeks. 80% of healthy pregnancies will deliver between 38 and 42 weeks. The smallest percentage is after 42 weeks, about 1-3%.

    - Mary Murry mayoclinic.com

  • December 27, 2008 7:03 p.m.

    I'm in my 24th week of pregnancy and was told after my ultrasound that the baby has a couple of 'calcium deposits' in its heart. I am scheduled for an advanced ultrasound. What does the presence of these calcium spots mean?? Some place I read it indicates DS. Thanks.

    - laura

  • December 24, 2008 12:36 a.m.

    I wondered the same thing. Perhaps those are miscarriages? Or early C-sections/inductions?

    - Sara

  • December 21, 2008 10:26 p.m.

    What happens to the other 10%?

    - Jaynee Weiss

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