? Re: mother's size and ability to push out 'big' baby

Specialties CNM

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So ive been hearing a lot about ' oh she's too short or small to have a lady partsl birth bc the baby is too big' lately. Can you decide if the mother's birth canal is too small based on the mother's exterior(ht/ wt/ )? Is that clinically possible? I thought you would have to do an internal exam to see about the pelvic size?

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Specializes in OB-Gyn/Primary Care/Ambulatory Leadership.

There is actually research out there (you can find it if you do a pubmed search) that correlates a woman's shoe size with her ability to deliver a child lady partslly. I remember searching for it after I had a doctor who told me to ask the patient her shoe size, because he held the belief that if her shoes were less than size 5, she would not be able to do it.

Alas, I cannot remember what the research determined!

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So Ive been hearing a lot about ' oh she's too short or small to have a lady partsl birth bc the baby is too big' lately. Can you decide if the mother's birth canal is too small based on the mother's exterior(ht/ wt/ )? Is that clinically possible? I thought you would have to do an internal exam to see about the pelvic size?

I know that a few examples does not make a rule, but I am 5 foot 5 and weigh 135 pounds. I birthed babies of the following weights: 8# 12 oz, 12#, 11# 10oz, 9# 11 oz all lady partslly.

FWIW my shoe size is 8.

Who has big babies? Well obviously gestational diabetics, but otherwise in "my circle" of homebirth/midwife/doula/bradley birthers, you find a LOT of big babies- babies over 10 pounds are normal. My 12 pounder was probably heavier because he topped out the spring scale, and at his 3 day ped visit he was up to 12# 4oz (which was probably actually a decrease from his birth weight). My midwife delivered a 10 pound breech a month before me, and she also had a set of 8 pound twins. My midwife told me (and I have nothing to back it up) that she believed in the "fishtank philosophy" which explains that fish only grow as large as their tank allows. While I don't know if that's true, homebirth midwives tend to see very few cases of CPD and certainly not before labor (when the pelvis opens up and relaxes). The eternal skeptic in me thinks that the surge in CPD before labor has everything to do with the convenience of scheduling and the price brought by a c-section.:twocents:

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Specializes in Community, OB, Nursery.

I have seen many many short women - under 5 ft tall - birth 9- and 10-lb babies lady partslly. I have a hard time believing that short stature automatically translates into a c/section for CPD.

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Specializes in LDRP.

I am 5'1.5 and delivered a 10 lb 7oz baby lady partslly :)

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Specializes in ICU , NICU, cardiology, emergency, pool.

Hello,

you can use pelvimetry radio, or pelviscan to determine the size of the pelvis during the last week of pregnancy .

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Specializes in Labor and Delivery.

It is impossible to know until she is in labor. The pelvis of a primip has a miraculous ability to expand when the labor hormones get going. I honestly think that most women can deliver a 10lber lady partslly without surgical assistance if they have freedom of movement. It is harder to deliver bigger babies on your back with your coccyx immobilized in comparison to an upright or hands and knees position. Most Obs don't really use positional changes in mothers whereas most midwives know those tricks.

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If you ever have the good fortune to come across someone who knows pelvimetry well (and I mean manual pelv), have them explain it to you. It's also pretty comprehensively explained in the textbook 'heart and hands'. It's a fascinating sequence of hand movements to do an internal exam to determine the type of pelvis (there are four, and then there are combinations between them) and the size of the 'true pelvis' that the babe has to squeeze through. Interestingly enough, *sometimes* (RARELY -- DON'T YOU EVER USE THIS TO TELL A WOMAN HER PELVIS MIGHT BE TOO SMALL FOR A lady partsL DELIVERY! I WILL FIND YOU AND GIVE YOU THE WHAT-FER!) the widest 'child-birthing' hips are the platypelloid type of pelvis, which has quite a small, oblong outlet and can forecast a very painful/difficult labor.

Pelvimetry should be done around wk 34/35, I think - the pelvis is starting to expand due to hormone load.

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The exterior dimensions have nothing to do with the interior dimensions. "Big baby" is a convenient excuse that also puts the blame on the mother instead of on the provider who induced, epiduraled, AROMed and whatever that lead to the mom's inability to give birth lady partslly. I work in a high volume practice and unfortunately see it a lot.

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