36 Week Sono - 34 Wk Head Measurement?

Updated on October 14, 2009
T.B. asks from Riverhead, NY
13 answers

I had my 36 week sono and i watched the screen. The tech took 3 measurements of the head. One measured 33 wks+ gestational age, one 34 + wks and one 35 + wks. The leg bones were measuring 37 wks. I didn't notice her measuring the belly. She said the baby weighs 5 lbs 6oz. Later when i saw the doc, he said the fluid levels are good, measurements are good...on the small side, but ok. I don't believe him. Why is the head measuring behind? My due date is dead-on accurate....i did ovulation tests and new exactly when i got pregnant. Has anyone else experienced smaller than gestational age head circumference and what happened?

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S.H.

answers from New York on

MY sons head measured much larger then it should have been and the sono tech kept taking all these measurements and looking concerned and calling people in and when I asked they said that the head is measuring larger then it should...... advised with a smile that my husband has a bigger head. My son is fine and when he turned 1 he was wearing a 2t/3t hat ...... maybe someone is on the small side and the baby is taking after them ....... I am sure every thing will be wonderful.

Best of luck!!!

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T.D.

answers from Dallas on

Dear T.,

You have a right to be concerned but do try to take the sono information in stride. To avoid malpractice the doctor would have definitely ordered a fetal C-SCAN if he felt there was a possible anomaly that needed interpretation.

When I was 7 months pregnant the sono showed a gap in my daughters developing cerebellum, they immediately ordered a fetal cat scan and scared the hell out of us , saying that the gap in her brain was going to cause retardation and developmental delays as well as facial disfigurement. We were shocked, sad and furthermnore the next sono the technician informed us that the thigh bones or femurs were very short. For the rest of the pregnancy we spent our time preparing ourselves for the worst. (I had already given birth to a very severely affected child with cerebral palsy with my ex-husband 11 years prior) It was hell.

But... after our child was born lo and behold her newborn C-Scan showed only very slight variation and they then told us to expect her to live a very normal life.HA! We felt like we won the lottery, but finally the neonatologist let us in on a little secret...those sonos are frequently miscontrued even by technicians because they are viewing a developing child, therefore parts of the body sometimes need to catch up and any bigmouth tech can strike a parent with abject horror and doubt.

If what I say doesn't bring you any relief I understand, you may need to seek a second opinion, you can always do that.

I wish you the very best for you and your baby, sister!

T.

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A.T.

answers from Buffalo on

The measurements are just averages. A lot will depend on how short or tall or round your and your husband's heads are. Some people have naturally larger heads and others have little things. My neighbors joke that their youngest son's head was the same size from birth until he was three because he had such a big head and it took time to grow into it.

With my oldest there was a lot of discrepancies about where I was in the pregnancy based on his size. They changed the due date several times even though I knew when my last period started and ended and the only two days I could've gotten pregnant after that.

When I finally went into labor, I was almost three weeks past my due date. I had to go that long because it was after a hurricane and my doctor's office, hospital, and my home were all damaged so I was forced to go to a clinic near where I was then staying. The doctor that delivered my son insisted he was right on time because there wasn't much vernix on his body and I must've mixed up dates (not a chance). My son was 8 1/2 lbs and 21" long. Average but on the higher end of average. I'm only 5'2" and my husband is 5'6" and my second son was two weeks late delivered by C-section and he was almost identical in size. My third son was almost two weeks early and he was only 6 lbs 3 oz, so it all adds up as he was late. All my kids were kinda screwy on their sizes and never quite matched up to where we KNEW I was in my pregnancy. (I can tell you exactly where and when for each conception.) They're also all healthy and growing as expected.

What's it all mean about sizes then? That they're just a standard. An average. I wouldn't stress about it. That's why the doctor told you it's ok. The difference between 34 weeks and 36 weeks measurements is really minute, all measured in cm which are fractions of an inch. One cm equals 0.393700787 inches so don't fret.

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R.D.

answers from New York on

Hi T.,
My sono showed my son had a big head and i freaked! He is totally fine and is 4 and yes his head is a tad big...as are all of ours in the family. I mean look around tomorrow and you will see how many diff size shapes and heads there are. They also measured him to be over 9 pounds and he was 7 and 14 ounces. So, yes, they can be way off and the bigger the baby gets the harder the read is. I would trust the doctor on this one!

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C.O.

answers from New York on

I wouldn't worry. My first was born 4 days early and was 7lbs 9oz and 20 inches long. My second was born 10 days early and was 9lbs 3oz and 20.75 inches long. The same differences go for head circumfrence, etc. And with both my pregnancies due date were established early on by my dates and confirmed by ultrasound.
The truth is that kids are all different, sonogram is only 75-90% accurate. And the later you have your sonogram the wider the normal range. You have had a normal pregnancy and that should be all you focus on.
Every child is different and every pregnancy. All the hard and fast rules of what size a child should be just serve to stress mom out!

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J.M.

answers from New York on

Dear T.,
I see patients' ultrasound reports every day and it is quite "normal" to see variation in measurments between one part of the body to the next. We certainly pay attention if a measurement is >97% or <5th percentile and the rest of the measurements are more typical. We also pay attention if some part was measuring at a specific percentile and then started dramatically changing (for example, if the femur was 50th percentile at 16 and 22 weeks and then less than 10th percentile at 26 weeks). For all you know, you and/or your partner may have a head that is smaller (percentile) than your other measurements! Just because it measures a little smaller on ultrasound does NOT mean that it will look smaller in the real world. If you're really worried, ask to speak with your phsyician again.
Best wishes.
J.

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D.

answers from New York on

My kids did measure pretty much right on the money. But they do have very small heads. My daughter's head was so small, that at 6 mos a newborn hat kept falling down over her eyes. And for both my kids their heads measure around the 4th percentile. My 5 yr old can still fit in a 3T hat. And it don't know if it's head size or what, but both my kids are very bright. They both spoke early, and spoke in fully formed sentences very young. Besides, a smaller head will make it hurt a whole lot less when you go to deliver (lol). If the doctor isn't worried, I wouldn't be. Oh, when my friend was pregnant with her daughter, they told her that she was about 8lbs. Alexa was 10lbs. 5 oz. So, don't worry.

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D.D.

answers from New York on

dont stress over it...just enjoy the last weeks of your pregnancy and welcome that beautiful new baby soon!

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J.C.

answers from New York on

Keep in mind that the doctor is legally bound to tell you the truth - good news or bad.

Also keep in mind that sonograms are not exact tools. Babies move, pictures are blurry and maybe the tech was the bottom of his class.

Don't get too upset. Call your doctor if you have anymore questions. That's why you pay them!

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K.H.

answers from Utica on

Hi T.
Congratulations on the new baby.
Sometimes when you know how to read the measurements and you don't know the ranges you end up in an unnecessary mess. Sometimes they turn the screen so you can't read the results for just that reason. If the OB thought there was trouble he would have sent you to Neonatal care. They did me, but all was well. My twins were fine.
God bless you and give you peace.
K.

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A.H.

answers from New York on

I wouldn't consider your baby's head measurement to be "behind". Remember that all of these measurements are averages and every size from the 0 percentile to the 100 percentile are still in the range of normal. For instance, when I had my 19 week sonogram done, my daughters head measurement was in the 90th percentile and her femur was in the 20th. My girlfriends baby, who was conceived at exactly the same time (we delivered within 9 hours of each other) had a baby who's head measurement was in the 20th percentile and who's abdomen was in the 90th. We joked that hers baby would look like a pumpkin and mine like a lollypop. Of course, I was concerned, mostly about birthing what appeared to be such a large head. In the end, both babies were born easily... her's weighed 7lbs 1 oz and mine weighed 8 lbs 6 oz. Now, my daughters head is only in the 15th percentile. For the whole first year of her life, her height and weight were almost in the 100th percentile and now, they are both around the 20th. Anyway, this is a lot of jargon about percentages and likely tedious to read but hopefully it is example enough to you that these measurements have such a wide range of normal and a 34 week head measurement along with a 37 week femur measurement doesn't mean anything concerning. I'll bet you $100 that you won't feel that your baby's head is small in a month when you deliver! Really, don't worry... it is all fine.

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M.S.

answers from New York on

My OB told me that the only really good measurement of the baby cn be done when the baby is outside the tummy... your doc didnt seem to be alarmed, but if you are worried, ask questions, that's what you pay him/her for.
congrats on the pregnancy and good luck with the birth in about 1 month...

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R.E.

answers from New York on

at this point in your pregnancy, u/s is not precise. There is no question that if the doctor thought there was ANY concern, you would be already be schedule for a repeat u/s and perhaps other tests.

Your baby is likely just developing into the genetic pattern he/she is meant to be in. Some babies have bigger heads, some smaller. With labor approaching, I would celebrate the fact that they did not tell you that you are 36 weeks with a head measuring 40 weeks!!!

This is all coming from a momma with 3 kids with little heads - my boys were both in the 50th %ile for height and weight but their heads were around the 25th %ile. DD was around 40th for ht/wt but 10th for head. Compare this to my niece who was 75th %ile for wt with a head that was off the charts!

Enjoy the last few weeks of your pregnancy :-)

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