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    Becca1025's Avatar
    Becca1025 Posts: 422, Reputation: 45
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    #1

    Sep 28, 2007, 07:44 AM
    How accurate are ultrasounds?
    So when I found out I was pregnant and went to my first obgyn appointment, I was told I was 7 weeks. Well awhile later I experienced some bleeding and went to the E.R and with my calculations I was 10 weeks at the time. Everything turned out fine, but the ultrasound people told me I was barely 9 weeks. Then I went for another ultrasound when I was supposed to be 10 weeks and 6 days, but then that ultrasound said I was 11 weeks and 5 days. My due date just kept bouncing between January 9 or Jan 16. So then I got another ultrasound at 18 weeks and was then told I was 17 weeks. Then I went back and got another ultrasound four weeks later and I was supposed to be 21 weeks but I was at 22 weeks. The following week I went to a doctors appointment (my doctor was out of town, so I saw her P.A that day) and she came in saying "So you're 23 weeks and 6 days" which was a few days off what I thought, but not a big deal. So I started going by her calculations. Then I went to the doctors yesterday for fetal monitoring (hadn't felt the baby for awhile, but everything is fine), and I was supposed to be at 25 weeks, but nurse said "no you're not you're 24 weeks" and then I explained to her how all the ultrasounds gave me different weeks and she said "ultrasounds are not accurate" and to just go by the given due date. Then I told her I was going by the doctors calculations. She said the only accurate calculations was my due date, but my due date keeps going back and fourth... I always thought ultrasound were there for the accuracy... So what would you go by, the ultrasound, the doctor, the due date? The baby has been measuring big so I don't know how the due date is now...
    buggage's Avatar
    buggage Posts: 1,514, Reputation: 165
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    #2

    Sep 28, 2007, 08:01 AM
    The important thing to remember is that a due date is simply an expected date of birth going by your last menstrual period, giving the baby an average of 40 weeks to develop and grow, before they are born. Since every woman ovulates at different times, your conception dates will all be different.you could conceive immediately after your period is over(or even while on your period) and another woman could conceive only a few days before her expected period, or in mid cycle.(and not every woman goes by a 28 day cycle, so are less, and some go longer. I for example am 32 days. That throws things off as well) you could see how this would cause your true due date to differ. But there is really no SURE way to determine the exact date of conception, SO they go from the last date of your period. And all babies develop at an average pace, but some are a little more ready, or less ready toward the end of pregnancy. Basically the due date is just giving the doctors a time line, so they can make sure that baby is as healthy as they could possibly be, before they are born. Or in the case of going over due, they don't want baby to stay in too long, and they may need to induce labor for babies safety. The ultrasounds are pretty accurate, as you can actually see the baby, and you aren't observing everything the outside of the belly. Just looking at some women you would swear that they are farther or shorter along then they really are. It all depends on how you carry, how big your baby is, the weight gain etc. So measuring from the outside is not always accurate. Its just an estimate to help, just like the due date. The ultrasounds look at how big the baby is, how the organs etc are developing. Now, things is every 100%(ask any parent who was told they were having a boy, and ended up with a girl, or vice versa) but I would be more inclined to believe the ultrasounds. Due dates are always off, and having your baby on their true due date like I did with my second one, is really a rarity. Try not to take anything too literally. It's nice to know a good date to when your baby will be here, but so long as they are keeping an eye on baby's health, and making sure everything is progressing as it should, then there really is no need for worry.
    macksmom's Avatar
    macksmom Posts: 1,787, Reputation: 152
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    #3

    Sep 28, 2007, 09:04 AM
    Ultrasounds determine gestastional age by size/measurements. Just like when they measure your stomach... you are ideally supposed to measuer in inches how many weeks pregnant you are (ex. At 28 weeks, your stomach should measure 28 inches).

    As hard as they may try, no one can tell you EXACTLY how far along you are. They can give estimates based on your last period, and the size of the baby.

    For example... when I got pregnant with my daughter, I was on birth control pills, and hadn't had a period in at least 6 months. Thus, they couldn't go by my last period, so the best they could do was go by the size of the baby at the first ultrasound. They gave me a due date of January 11th and informed me that most first time moms go to their due date if not beyond. I gained a lot of wieght, and my stomach was measuring big. They were worried that my daughter was going to be a big baby.

    Well, I delivered on December 31st... almost 2 weeks before I was due, and my daughter was only 6lbs 7oz and 19inches... not a big baby at all.

    The dates they are giving you are not far off... one doctor isn't saying your due date is January 16th and another telling you it's February 16th... then I would think there's a problem... your looking at a difference of a few days-week. And most likely, as Buggage said... the chances that you actually deliver on any of the given due dates is rare.
    Becca1025's Avatar
    Becca1025 Posts: 422, Reputation: 45
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    #4

    Sep 30, 2007, 08:54 AM
    I know chances of my baby coming on the actual due date is like 5% or even less. I just want to know which is a more accurate reading. I think having my due date or how many weeks I actually am, off a week one month, then off two weeks the next month over and over again is a lot to me. I would just like to know how many weeks I actually am instead of saying "I don't know either this much or this much." I just really want to know which is the most accurate, doctor measurments (with that tape measure), an ultrasound, or just follow the original due date?
    buggage's Avatar
    buggage Posts: 1,514, Reputation: 165
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    #5

    Sep 30, 2007, 05:58 PM
    Ask your doctor which would be best to go by
    Shawney's Avatar
    Shawney Posts: 1, Reputation: 1
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    #6

    Oct 16, 2011, 07:37 AM
    Oky I had sex on 6/1/2011 and period came on 6/4/2011 and went off 6/4/2011 and I had sex 6/27/2011 and missed my period in the beginning of July so I went to get tested on 7/15/2011 they told me I was 5wks pregnant so I'm confuse
    DoulaLC's Avatar
    DoulaLC Posts: 10,488, Reputation: 1952
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    #7

    Oct 16, 2011, 08:18 AM
    Quote Originally Posted by Shawney View Post
    Oky I had sex on 6/1/2011 and period came on 6/4/2011 and went off 6/4/2011 and I had sex 6/27/2011 and missed my period in the beginning of july so I went to get tested on 7/15/2011 they told me I was 5wks pregnant so im confuse

    If you became pregnant from the sex on 27 June, you would be around five weeks pregnant. If you had become pregnant from 1 June, you would be further along. If the period you had 4 June was about the time you would normally expect it, it is unlikely you would become pregnant from having had sex just a few days before as that would not be the norm for ovulation to occur (possible, but not probable).

    Were your cycles usually pretty regular? They may decide to do another ultrasound in a few weeks time and your dates may be altered a bit, which is not uncommon. Dating and sizing with ultrasound is not an exact science, but it is the most accurate of tools available in earlier pregnancy.
    renatta_28's Avatar
    renatta_28 Posts: 3, Reputation: 1
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    #8

    Feb 8, 2012, 08:11 PM
    Hello, I just was told I am 32 weeks and 6 days today I am confused my last period was July 4th 2011. My doctor said I was due April 10th but the ultrasound is showing that I am 32 weeks and 6 days? When did conceive?
    DoulaLC's Avatar
    DoulaLC Posts: 10,488, Reputation: 1952
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    #9

    Feb 12, 2012, 09:30 AM
    Quote Originally Posted by renatta_28 View Post
    hello, i just was told i am 32 weeks and 6 days today i am confused my last period was july 4th 2011. my doctor said i was due april 10th but the ultrasound is showing that i am 32 weeks and 6 days? when did concieve?

    You likely conceived sometime early July... or perhaps what you thought was a period was not and you had just recently become pregnant. Keep in mind that ultrasound is not an exact science and due dates are estimations. It would be perfectly normal, for example, for you to give birth somewhere between the end of March till a bit later in April.
    Your doctor gave a due date going with the last period... the ultrasound adjusted the dates a bit. If it was a period, you would most likely not have been pregnant just yet (most women aren't). This is why you have a window of time that is normal to give birth in towards the end of pregnancy.
    rar13's Avatar
    rar13 Posts: 5, Reputation: 1
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    #10

    May 2, 2012, 04:46 PM
    I was told on the 24th of April that I am 6 weeks and 4 days. My last normal period was on the 12th of February. I had my bleeding on 5th of March that came for one day (very light) went for a day and they came back the next morning and was gone. I feel as if I'm further along. Its now the 3rd of May and I am 7 weeks and 6 days according to the ultrasound could the ultrasound be wrong? :/
    DoulaLC's Avatar
    DoulaLC Posts: 10,488, Reputation: 1952
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    #11

    May 2, 2012, 05:10 PM
    Quote Originally Posted by rar13 View Post
    i was told on the 24th of April that i am 6 weeks and 4 days. My last normal period was on the 12th of February. I had my bleeding on 5th of March that came for one day (very light) went for a day and they came back the next morning and was gone. I feel as if im further along. its now the 3rd of May and i am 7 weeks and 6 days according to the ultrasound could the ultrasound be wrong? :/

    Ultrasound will usually be more accurate than going with the last period. This is because periods can be off or irregular from their norm. What you had in March, may indeed have been due to an off cycle. Babies also tend to develop pretty uniformly early in pregnancy. It is fairly well established what body parts will measure, and what can be seen on an ultrasound from week to week.

    Can they be wrong... yes, it is possible, but while they are not always going to be exact, they do offer the best means of dating a pregnancy.
    rar13's Avatar
    rar13 Posts: 5, Reputation: 1
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    #12

    May 2, 2012, 05:29 PM
    Thank you for your reply.. so your saying that the bleeding in march could have just been an irregular period? And I may have fell pregnant after this period? Also the tech had trouble measuring as the baby was sitting right up against the sack, could this may be a reason for an off date?
    DoulaLC's Avatar
    DoulaLC Posts: 10,488, Reputation: 1952
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    #13

    May 2, 2012, 05:34 PM
    Yes, you may have become pregnant after the March bleeding. If the tech had trouble measuring baby, they should do another scan. Did they mention having another done in a couple of weeks by chance? Did both of the dates you received come from ultrasounds? If so, they both would have been consistent with the dates given.

    You can always ask your doctor or midwife about having another scan done before too long. They may have a set schedule as to when they do them already. Around 12 weeks is another common time for scans. That would also give you a good indication of things have been on track with the dates already given or if they need to alter it a bit.
    rar13's Avatar
    rar13 Posts: 5, Reputation: 1
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    #14

    May 2, 2012, 05:45 PM
    Quote Originally Posted by DoulaLC View Post
    Yes, you may have become pregnant after the March bleeding. If the tech had trouble measuring baby, they should do another scan. Did they mention having another done in a couple of weeks by chance? Did both of the dates you received come from ultrasounds? If so, they both would have been consistent with the dates given.

    You can always ask your doctor or midwife about having another scan done before too long. They may have a set schedule as to when they do them already. Around 12 weeks is another common time for scans. That would also give you a good indication of things have been on track with the dates already given or if they need to alter it a bit.
    Yeah she mentioned that I may need one in a few more weeks maybe I should ask my gp to schedule another one. I only received one date and that was from the ultrasound I had which said I was 6 weeks and four days. The bleeding in march was very irregular and light I read that this could have been implantation bleeding as this was not when my period was due..
    rar13's Avatar
    rar13 Posts: 5, Reputation: 1
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    #15

    May 2, 2012, 05:47 PM
    I am also very petite and am starting to show a small bump..
    DoulaLC's Avatar
    DoulaLC Posts: 10,488, Reputation: 1952
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    #16

    May 2, 2012, 05:49 PM
    See what the next scan shows... first may have been off.
    FirstBaby's Avatar
    FirstBaby Posts: 1, Reputation: 1
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    #17

    May 7, 2012, 01:30 PM
    Help! I was told from my last period that I was 9 weeks but when I had my ultrasound last week she told me that I was showing 10 weeks with a baby measuring 10 centimeters. I;m so confused. How many weeks am I really?
    rar13's Avatar
    rar13 Posts: 5, Reputation: 1
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    #18

    May 7, 2012, 03:27 PM
    Your most likely 10 weeks, going from your period is not always correct as I was told by my GP that is just an estimate. After your period you could ovulate any time between the end of your period and your next period. Congratulations on the pregnancy :)

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