My Friend’s Baby Was Too Big for Their Pelvis…Will the Same Thing Happen to Me?
This is a common concern, especially during one's first pregnancy. It seems that everyone has a cousin or a best friend who had to have a c-section because their baby was too big. You should be relieved to know that this problem seems much more widespread than it actually is.
Two factors affect the ease with which the baby can be delivered vaginally: the first is of course the actual size and position of the baby, and the second is the structure of the expectant parent's pelvis. As you’re probably aware, there are certain conditions that can cause the baby to be too big for the pelvis. These conditions include gestational diabetes, and some disorders that cause abnormal fetal skull development. It is important to note that an ultrasound alone predicting a large baby is not as reliable as commonly thought. Ultrasound estimation of fetal weight is considered no more accurate than estimation obtained by Leopold’s Maneuver – that is, simply palpating for fetal size through the abdomen, and can be inaccurate by as much as 11.6 to 19.4 oz. 1,2 Additional good news for expectant parents - ultrasound prediction of high birth weight is not considered reason enough to undergo c-section delivery or induced labor, according to the American Academy of Family Physicians. 2
Barring any of the above conditions of gestational diabetes or abnormal fetal development, which are typically well-known if they are present, the structure of the pelvis is the only other variable in this situation. Pelvic shapes are classified according to the Caldwell and Moloy Classification system. The four basic pelvic shapes are Gynecoid, Android, Anthropoid, and Platypelloid. Of these four pelvic shapes, two of them are considered adequate for vaginal delivery – the Gynecoid and the Anthropoid. The Android and Platypelloid shapes typically have a poor prognosis for vaginal delivery. The good news, however, is that only 20% of women are thought to have the Android shape and only 5% are thought to have the Platypelloid shape. 3 That means that 75% of women are expected to (Anrig & Plaugher, 2013) have pelvic structures that favor vaginal deliveries! If your pelvic structure falls into the 25% with poor prognosis for vaginal delivery, then it is very important that you work closely with your partner and birth care provider to create the best birth plan possible given your circumstances. Whichever pelvis type you happen to have, the fact remains that Structural Shift may prove detrimental to your baby’s ability to grow and move properly within the womb. For this reason, it is important to receive regular Structural Chiropractic checkups throughout your pregnancy – regardless of how you may deliver – to help ensure that your baby has adequate room to move and develop. For more information on how Structural Shift can affect this aspect of pregnancy, be sure to ask your Structural Chiropractor and browse our other blog topics.
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Am Fam Physician.2001 Jul 1;64(1):169-170. 2. Am Fam Physician.2001 Jan 15;63(2):302-307. 3. Anrig, C., & Plaugher, G. (2013). Pediatric Chiropractic. Philadelphia: Lippincott Williams & Wilkins.