Head Circumference : Abdominal Circumference

[umsami]

Anybody know anything about the head circumference:abdominal circumference ratio?? When do they get concerned?? Mine is currently at 0.98...and my OB is starting to get a little worried regarding the abdominal circumference. (I have gestational diabetes.) DS2 was 9 lbs 14 oz... but big all over... so he just sort of plopped out pretty quickly.

[ckhagen]

I don't know a whole lot about it but I can tell you this...
I had to see a perinatologist for a consult on my VBAC and he did u/s measurements and told me that my son was in the mid-90th percentile in head measurements and even larger in abdominal measurements. He pulled out all kinds of charts to show me just how "huge" he was. He stated that there was no way my son would ever come out of me without surgery and that it would probably be wise to schedule a c-section at 38 weeks. I told him where to go...
Sure enough, I pushed him out with no tears. 9lbs even with a 12 3/4 (?) inch head. My first baby was 10lbs 8oz and had a 14.5in head, he was a c-section with an OB. The VBAC was in a FSBC with a very experienced midwife.

[mamaverdi]

What did your OB say it meant?

[tatermom]

I am having the EXACT same issue right now-- baby's abdominal circumference is quite a bit bigger than his head (somewhere in the upper 90's%ile) and I was told at my last u/s appt that I'd "be a good candidate for a c-section" :-- though they are going to do a follow-up u/s 37 wks (I'm at 34.5 wks now). I don't believe at all that it this is really an issue (seeing that u/s measurements may not be that accurate, and that baby may grow/change over the next 5 wks)... but this may preclude me from using the wonderful birth center I had planned on using (I think that anything above the 94% requires them to send me to a hospital l&d). I'll be interested to hear what others say...

[umsami]

I've found some stuff on AC determining macrosomia... in general, if it's over 35 cms, there's a good chance of a baby over 4000 g. They also say that induction of those babies increases the risk of shoulder dystocia.

Macrosomia Prediction Using Ultrasound Fetal Abdominal Circumference of 35 Centimeters or More
ALLAHYAR JAZAYERI, MD, PhD, JULIA A. HEFFRON, MD, ROSEMARY PHILLIPS, MD and WILLIAM N. SPELLACY, MD

From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Louisiana State University Medical Center, Shreveport, Louisiana, and Department of Obstetrics and Gynecology, College of Medicine, University of South Florida, Tampa, Florida.

Address reprint requests to: William N. Spellacy, MD, Suite 514, 4 Columbia Drive, Tampa, FL 33606

Objective: To determine if birth weights greater than 4000 g can be predicted by ultrasound measurements of abdominal circumferences.

Methods: In 1996, 254 newborns delivered at Tampa General Hospital weighed at least 4000 g, 84 of whom had ultrasound examinations within 2 weeks of delivery. Those were compared with 84 neonates with recent ultrasounds who weighed less than 4000 g. Data were abstracted retrospectively from maternal medical records.

Results: The best linear predictor of birth weight was ultrasound measurement of abdominal circumference (AC), which had a correlation coefficient of 0.95. An AC measurement of 35 cm or more predicted 93% of macrosomic infants. Among 177 macrosomic infants born vaginally, 23 (13%) had shoulder dystocia. In that group, induction of labor was associated with a greater than three-fold increase in risk of shoulder dystocia (odds ratio [OR] 3.4, 95% confidence interval [CI] 1.4, 8.2; P < .01). Labor augmentation was not associated with increased risk of shoulder dystocia.

Conclusion: Abdominal circumference measurements were useful in screening for suspected macrosomia. An AC measurement of 35 cm or more identified more than 90% of macrosomic infants who were at risk for shoulder dystocia. Induction of labor in macrosomic patients increased the risk of shoulder dystocia.

[MsElle07]

OK, I'm not getting why the abdominal measurement would matter so much? Fat is squishy! It's not the baby's tummy that is hard to push out. I've had two babies that were over 9lbs... trust me, the baby's stomach is not the hard part!

[lyttlewon]

I was thinking the same thing.

Originally Posted by MsElle07

OK, I'm not getting why the abdominal measurement would matter so much? Fat is squishy! It's not the baby's tummy that is hard to push out. I've had two babies that were over 9lbs... trust me, the baby's stomach is not the hard part!

[tatermom]

As far as I can tell, the abdominal circumference is used as a proxy for shoulder width, so they're worried about shoulder dysplasia.

[MsElle07]

Shoulder dystocia occurs in average weight babies more than 50% of the time. It's largely about the baby's position. Also, the measurements of the baby do not show how expandable the mother's pelvis is. If she's off her tailbone during pushing, her pelvis can expand an additional 30% beyond what it would otherwise be during labor (which is already bigger than her non-pregnant state).

[mama to 2 girls]

I don't know about when they get concerned but let me tell you that ultrasounds are notoriously off! My cousin had an ultrasound with her 2nd and was told his head was in the 90th percentile, well when he was born he was on the "bigger" side at 9lbs. 10oz but he had almost the same measurements as my almost 8lber! Her 9lber's head was ONLY 14"! So much for him having a big head! My 8lber and her 9lber had the same chest cir. and the same stomach cir....

My 8lber. had a 13 1/2" head.

[ckhagen]

Originally Posted by mamaverdi

What did your OB say it meant?

Well, he was just an OB I was seeing for a consult, thank God I had no plans of delivering with him. He basically told me it meant the kid would be huge and like a pp said, was using it as a proxy for SD. He also said it indicated that I was probably a gestational diabetic regardless of the fact that I had pass the GTT with absolutely no trouble. IIRC he pointed out that the measurments, in conjunction with one another, nearly assured me of a macrosomic baby close to 11lbs.

[Autumn Breeze]

It's almost completely about the baby's position.

http://www.spinningbabies.com

Go there, position your baby!!!

FWIW, my ds had a 14 inch head, and like 13 inch chest and abdomen. Took me 2 hours, flat on my back pushing with my body, then w/ vaccum extraction to push him out. My daughter had a 15 inch head, 14 inch body and abdomen, labor was 28 minutes. Go figure.


Then again, I don't usually advocate for late term ultrasouns, as they are incredibly inaccurate.

[tatermom]

Originally Posted by ckhagen

Well, he was just an OB I was seeing for a consult, thank God I had no plans of delivering with him. He basically told me it meant the kid would be huge and like a pp said, was using it as a proxy for SD. He also said it indicated that I was probably a gestational diabetic regardless of the fact that I had pass the GTT with absolutely no trouble. IIRC he pointed out that the measurments, in conjunction with one another, nearly assured me of a macrosomic baby close to 11lbs.

HA! This is almost exactly what I was told, word for word-- I even just retook the GTT to prove (again) that I was not diabetic because they said that was the most likely explanation. Bah. I don't think that measurement really means anything-- it's just another statistics that doctors wish could give them some kind of predictive power over the birth. Fortunately my midwife feels the same way and is totally fighting for me on this... the whole thing is just so annoying!

[turtlewomyn]

My CNM and her OB used this as part of the way to coerce me into a c-section for fetal macrosomia. First they talked about hte weight (9lb10oz estimated by U/S, 9lb8.5oz actual) and then the OB said that the AC:HC ratio was an even better predictor of Shoulder Dystocia (he cited a study, but I don't have it). They also claimed that they had missed GD in me, as this is most likely to occur with GD, and that there was no way to tell at 40 weeks if I had it. I have since gotten a hold of my records (my GTT was 67 way below the cut off of 140) and have found out they could have redone the GTT, so that was a lie. Some women are just genetically predisposed to having big babies (I had nine and ten pound cousins born vaginally) and so they are made to birth those babies.

To the OP: If you haven't already you should look at Kmom's website: www.plus-size-pregnancy.org it has great info for pregnant women of all sizes, including information on GD. I am concerned that your care provider is going to try to coerce you into a c-section. You already pushed out an almost 10 pounder, no problem, your body was made to birth big babies. However, since you may be at slightly greater risk for SD, you should try to stay off your back to give birth (if you weren't planning to already). I would also be nervous about this particular care provider, find out how much experience they have with resolving shoulder dystocia. They should know how to do the Gaskin Manuever and/or the McRoberts Maneuver. If they start telling you horror stories about using the Zavenelli(sp?) Maneuver (pushing baby back up and performing an emergency c-section) I would find another care provider (preferably a homebirth midwife). That should only be done as a very last resort, as it has its own risks, and I wouldn't trust a care provider that uses it on a regular basis to resolve SD.

[lexbeach]

This thread is really interesting to me.

My baby was supposedly "macrosomic." I did not have GD. I passed the test easily, and my baby did too (they tested his blood sugar levels a bunch after he was born). He weighed 10 lbs., 9.5 oz and had a 40 cm (almost 16 inches) head, and a 41 cm chest. I had a c-section.

I had actually had an ultrasound a week before my baby was born (so at 39 weeks), and no one mentioned anything about measurements or ratios. I think that they are so frequently inaccurate.

My gut told me that my baby's head was huge. The birth went exactly the way that I knew it would, and it seemed as though a birth by c-section was the right way to go for my baby (of course, I will never really know absolutely for sure).

My experience did not make me less trusting of birth at all. Rather, I feel even MORE trusting of birth AND the fact that a pregnant mom knows best about what the deal is with her baby. I am still a firm believer in natural birth and the fact that "babies come out." I wouldn't listen to any statistics about measurements and shoulder dyscotia or OB advice. I would just listen to yourself. Listen to your baby.

Lex

[Autumn Breeze]

Lex, your 100% correct. We must listen too and trust our bodies. So much of that is lost in the way the medical community talks to and 'educates' us.

[ckhagen]

Lex,
What you described was actually very similar to my situation with DS1. I passed the GTT with very low numbers.
For weeks and weeks I kept telling my OB that I felt like he was huge... I could just "feel" it. I tried and tried to convince myself that he wasn't, but I couldn't. She checked by u/s, by palpation, even up to the day he was born they swore to me he was definitely NOT over 7.5 pounds. I disagreed, but accepted that they must know what they're talking about, right?
Sure enough, after being confined to a bed for 38 hours as part of an induction, I was c-sectioned and out came a (malpositioned) 10lb8oz baby. I DO think that I could have pushed him out, but it still amazes me to this day that she was 3lbs off.

Of course, my previous post shows that DS2 was completely the opposite story.