Gestational Age Older on Ultrasound

As stated in the other post, ultrasounds area tool but not all inclusive when making determinations of age, weight, etc.

Do not depend on this entirely. I had an u/s at 37 weeks and due to it showing my son to be 5 lb. 8 oz. it brought a whole course of action that eventually led to 2 inductions and finally a c-section. I delivered a baby boy that was 6 lb. 10 oz. 2 weeks later that ended up in the NICU due to those actions.

Advice: Use the u/s as a guide ONLY!

I have worked as an OB nurse in the past (not real recently) and what we were taught was that u/s before 20 weeks is pretty accurate on predicting gestational age. After that, because babies grow at VERY different rates, they aren't as accurate for gestational age. As for weight, u/s can vary 2 pounds in either direction.

I had my kids before u/s was in high use, but my OB said because I was so big (and had delivered #1 10 days early) that I wouldn't make my due date. I had him ON the due date. And yes, he was big, but not "too big". He was the right size for himself.

Trust that God knows what you and your baby need. I remember wanting that second one to come earlier, because I was tired of being pg, but it happened the way it was supposed to.

Ultrasound is not an exact science. It a group of measurements compared against known averages and is only as good as the experience of the person reading the information. There is controversy about the actual usefulness of ultrasound in a normal pregnancy.

Due to difference in growth rates, conception dates, and normal variations in the size of babies...yeah, they can be wrong on every aspect. The potential for deviation from the average increases as your pregnancy progresses. Your baby is becoming the sum of his individual genetic make-up...rather than being a mass of undifferentiated cells.

The real question is, do you have an idea of when you conceived? I knew exactly the first day I could have conceived, but had an u/s tech insist that I was a week further along...completely and utterly impossible. I delivered a 6lb 7oz girl at 37.5 weeks...so much for that 8 pound baby that was predicted.

Due dates are usually calculated at 40 weeks, but full term is 38-42 weeks. So assuming your doctor uses the 40 week date, you certainly could deliver before your "due" date.

This is normal. My friend is an OB/Gyn and said that the first trimester u/s is the most accurate for determining gestational age. What measurement was the Dr. using to determine gestational age at the last u/s? With my oldest child- the Dr. changed my due date based on a third trimester u/s. But he was born much closer to the original due date than to the revised due date.

As far as weight goes- it is just an estimation. U/S does not measure body mass (imagine a long and lean baby vs. a shorter chunkier baby or any combination in between and you can see the difficulty in measuring their weight in the uterus.) Not only that, but some Dr.s/techs are better than others at estimating. HOpe this has been helpful.

Ultrasounds to determine GA late in pregnancy are not at all accurate. You won't know your true date until labor begins :) Babies grow at different rates just like people do. The American College of Obstetrics and Gynecology does not recommend doing Ultrasounds to determine GA or weight. Ultrasound is way over used and is being used for purposes that it was never intended for. Also, when you had that US done your baby may have just gone through a growth spurt and if you had one done now it would show not as much growth. My advice to you is to stay away from the ultrasound machine and relax and wait for mother nature to take its course. Your body will not grow a baby too big your body to push out.

Lisa

P.S. Doctors will typically use the "you have low amniotic fluid" excuse to induce early. You can always increase your amniotic fluid by drinking more water. Also, as you approach term the fluid level usually drops anyway so this is not a valid reason to induce.

P.P.S. I also read another response on here from a mom that said she had to be induced because her baby did not want to come out even after her due date. Babies always eventually come out. How many women do you know that have been pregnant for years because they never went into labor? The "due date" is just an estimation date not an expiration date. Some babies are not ready to be born until 42 weeks.

Both my kids were considered older in the ultrasounds, both predicted to be big. Not the case thought, both boys weighed about 8 lbs and I had to be induced because neither wanted to come out even after my due date. Good luck on your new little one!

Not sure whether the gestational age is more accurate later in pregnancy (like you are now) or at the 20ish week anatomy scan, but I DO know that the ultrasound can be up to 1 1/2 POUNDS off in either direction. It scans bones best and so the fat baby is putting on can't be measured as accurately. They guessed around 9 pounds with my first (probably also because both my sister and I were a little over 9lbs at birth and my daughter ended up being 10lbs 7oz! (no, I did not have gestational diabetes ;) )
I would not worry about the overall weight of your baby, just let him come out when he is ready. :) I know it is hard at this time, I am currently 39 1/2 weeks with my second daughter (and a little worried she's going to be an 11 pounder!). I feel so huge!
Good luck!

More than likely, you just have a bigger baby. They measure gestational age by length and wt estimates. And that is all they are, estimates.

They estimated ALL 3 of my boys on the 7# range and were wrong all 3 times. My oldest was 9# even, my 2nd 6# even (he was 6 weeks premature- cannot imagine how big he would have been had he gone full term) and my youngest at 8#12 and a week early.

Ultrasounds at 6-9 weeks are the most accurate. I have had U/S at 6 weeks where my conception date was different then they assume with LMP and the U/S backed up my estimated due date (not theirs) within 3 days. Going by LMP they have been off by a week or more! So clearly LMP is not the best way to determine due date.

Later on in the pregnancy all babies are different sizes! It is the size of the baby that they use to determine the age of the baby. A friend of mine had a baby yesterday, close to due date, and he was only 6 lbs and 20 inches. So you can't judge gestational age by size. Ultrasounds can be off at that point by 3 pounds in either direction, as you experienced.

Anyway, I wouldn't worry about the ultrasound, it's not an accurate diagnostic tool as you discovered with your first baby. I've had 30 or so ultrasounds, and the early ones (6-9 weeks) were accurate but the later ones were not. I had an ultrasound that showed my baby would be 9 1/2 lbs at birth, the next showed I would be 8 lbs at due date, the next (while I was in labor one day after my due date) showed 38 weeks and 7 1/2 lbs. I was 40 weeks and he was nearly 10 lbs!

Yes, the gestational age is as inaccurate as the size!

U/s can have a 20% difference (either way) in weight and can be up to two weeks (either way) off by age. All 3 of my children showed bigger and older than they actually were! My first was 10 days early and was 5 lbs 4 ozs. with an early date, but was expected to be AT LEAST 8.5 lbs! My second was a day late and was 6 lbs 13 ozs and had an older gestational date. My last one was supposedly 7 lbs 11 ozs at 36 weeks and was only 7 lbs when she was born at 38 weeks. Try not to worry and that beautiful baby will come when they need to.

my first son was 9lbs. 1.oz which by the ultra sound said he would weigh. this is my second and she is measuring a week larger than she is. i know when my last period was and that she is going to be a large baby. people ask me if they moved the date due to her size. no they dont move the date because the baby is large. btw my son was enduced a day after his due date. congrats.