Short Women And Big Babies

 

I get frustrated at the whole OB mentality of being able to "eyeball" a woman and decide what her chances of a vaginal birth are.

I once had a student approach me in class telling me that she had had three different OB's in her lifetime tell her that she would need a c-section because she was short. (note, she wasn't _incredibly_ short... I'm guessing 4'11 or so)

I once had a mom who at the baby reunion told us that she had a c-section for a baby that was too big for her to deliver... but she'd kind of expected that, because her OB had told her during pregnancy that she had a small pelvis and was likely to need a c-section.

I doubted that there was any research validity for these ideas, but today's message prompted me to actually go and research this.

 

The summary is here, the details below

 

First question: what is cephalo-pelvic disproportion and how is it defined? Basically, if there's a labor that is not progressing, it is _assumed_ due to the baby's size or the shape of the pelvis, so CPD is really a diagnosis of failure to progress.

Can CPD be predicted? There have been attempts to use xray pelvimetry, computer programs, and other means to predict CPD and cesarean. Mixed results. (Be aware that it's also hard to predict what the baby's weight is going to be: ultrasound has a margin of error of up to two pounds in either direction!)

Is CPD more likely for shorter women? there have been some studies which indicate an increased likelihood for smaller women, but it's not a clear-cut issue. What's your role as doula? (this answer is my opinion, not the research) During her pregnancy: do all within your power to encourage women prior to the birth, reassuring them that it is fully possible for small women to birth large babies vaginally: give them faith in their own bodies. During early labor: do all within your power to help labor move along and avoid failure to progress, also be prepared to advocate for patience in the diagnosis of failure to progress (encourage caregivers to use Alber's data on the labor curve, not Friedman's!, to judge normal length of labor.) During second stage: if they do have a big baby, delivering on hands and knees does seem to reduce the risk of shoulder dystocia, one of the concerns with big babies.

 

More details:

 

Defining CPD

"The diagnostic criteria for cephalopelvic disproportion were cervical dilation arrested after 5 cm, unresponsive to oxytocin augmentation, after active dilatation of 2 cm or more in 2 hours. Fetal malpresentations and malpositions were excluded." Impey L, O'Herlihy C. First delivery after cesarean delivery for strictly defined cephalopelvic disproportion. Obstet Gynecol 1998 Nov;92(5):799-803 "Friedman found that up to 30% of women with protraction disorders had cephalopelvic disproportion. " (protraction disorder = dilation of less than 1.2 cm per hour in active labor for nulliparas, 1.5 for multips) "Up to 50%" of arrest disorders are for CPD (arrest disorder = dilation stopped for more than two hours, or descent stopped for more than one

hour) This information was taken from a website that is no longer available: (http://www.library.uthscsa.edu/ms2/ICS/Female%20Reproductive/Tables/Abnormal%20Labor.doc)

 

One site defines CPD as an issue of size, but then implies that it is merely a synonym for a stalled-out, failure to progress labor "Cephalopelvic disproportion is a disparity between the size of the maternal pelvis and the fetal head that precludes vaginal delivery. This condition can rarely be diagnosed in advance. The term "failure to progress" should no longer be used." http://www.medical-library.org/journals2a/dystocia.htm

babydirectory.com says CPD "is a medical term which refers to the baby's head being unable to pass safely through the mother's pelvis during delivery and birth. ... Unless, for example, a woman knows she has a narrow pelvic outlet and the baby is large, cephalopelvic disproportion won't become apparent until the head fails to engage some time after 36 weeks of pregnancy." They say that if baby is not engaged by week 38, it may be due to CPD.

 

Predicting CPD:

One study shows no good means for predicting: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&lis

t_uids=12076922&dopt=Abstract

Another study shows postpartum x-ray pelvimetry will help to predict http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&lis

t_uids=12418069&dopt=Abstract

 

Who is more likely to have CPD? (And what do we know about shorter women's labors)

 

There is research that shows that obese women are more likely to have c-sections for CPD "In our practice, the primiparous woman whose body mass index is >30 kg/m(2) is six times more likely to have a cesarean delivery for the diagnosis of cephalopelvic disproportion/failure to progress than the primiparous woman whose body mass index is <20 kg/m(2)." Young TK, Woodmansee B.Factors that are associated with cesarean delivery in a large private practice: the importance of prepregnancy body mass index and weight gain. Am J Obstet Gynecol 2002 Aug;187(2):312-8; discussion 318-20.

 

There is research that shows more risk of "difficult delivery" (the abstract doesn't define this) for shorter women: "the risk of difficult delivery was increased for women with height less than 160 cm (odds ratio [OR] 2.1, 90% confidence interval [CI] 1.2, 3.4)"Fraser WD, Cayer M, Soeder BM, Turcot L, Marcoux S; PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group.Risk factors for difficult delivery in nulliparas with epidural analgesia in second stage of labor. Obstet Gynecol 2002 Mar;99(3):409-18 Related Articles, Links 

 

There is research that shows shorter women are more likely to get epidurals. Amongst a sample, "51.7% of these women used epidural analgesia. They were shorter (163 versus 165 cm, p = 0.002) ..." Dickinson JE, Godfrey M, Evans SF, Newnham JP. Factors influencing the selection of analgesia in spontaneously labouring nulliparous women at term. Aust N Z J Obstet Gynaecol 1997 Aug;37(3):289-93

 

There is one study that shows shorter women are more likely to be diagnosed with CPD: "Nulliparity (OR 4.0; CI 1.7-9.3; p = 0.0001), birthweight >or= 3400 g (OR 4.6; CI 2.1-10.0; p = 0.0001) and height <or= 154 cm (OR 3.8; CI 1.8-7.9; p = 0.0003) were associated with an increased risk of CPD"  Brabin L, Verhoeff F, Brabin BJ. Maternal height, birthweight and cephalo pelvic disproportion in urban Nigeria and rural Malawi. Acta Obstet Gynecol Scand 2002 Jun;81(6):502-7

 

 

Are there clear-cut cases of CPD?

 

Some babies are "too large" for passage through the pelvis due to medical reasons. For example: "Hydrocephalus, or excessive accumulation of CSF with enlargement of the cranium, occurs in 1 in 2,000 fetuses and accounts for about 12% of severe malformations found at birth. Because the diameter of the head may increase nearly two-fold, gross cephalopelvic disproportion results. "

Some pelves are "too small" for a normal size baby to pass through due to medical reasons:

"Absolute CPD can occur when the pelvis is contracted to the point where a normal-sized fetus is unable to traverse the canal." Sample causes include: rickets, poliomyelitis, pelvic fracture, tumors of the pelvis. One site states, but does not substantiate: "Dwarfs, as well as small and dysmorphic women, may also have pelves too small to allow passage."

(also taken from that now non-existent website)