VBAC Scare Tactics: Big Baby, Big Problems

by Kristen Oganowski, CD(DONA)

beautiful pregnant bellyMany women who want to have a vaginal birth after cesarean (or VBAC, pronounced "vee-back") in the U.S. and elsewhere have faced some sort of opposition from their care providers when they have expressed their desire to VBAC. Oftentimes, this opposition comes in the form of "VBAC scare tactics."

The (outrageous) statements are often misleading, exaggerated efforts by OBs (and yes, even midwives) to discourage women from VBAC and to encourage them to "choose" a repeat cesarean. (Of course, it's not really a choice if your provider won't even "let" you VBAC, is it?)

If you find yourself up against a barrage of scare tactics -- as I once did -- it can be exceedingly difficult to stake your claim and argue against the doctor (again, or midwife) who may or may not have your and your baby's health prioritized higher than medico-legal concerns and who may or may not be insinuating that VBACs are synonymous with driving your child in a car without a car seat.

If you do find yourself facing such scare tactics, and if you do want to have a VBAC, there are some questions that your care provider should be able to answer when s/he hurls those scary and/or outrageous comments and standards your way. And if s/he refuses to or even cannot answer these questions, then you might want to consider finding an alternative care provider -- one who is making medical decisions based on research, evidence, and even respect for your patient autonomy and not on fear, willful ignorance, or even convenience.

I encourage all mothers who read this post (and others in my "VBAC Scare Tactics Series") to take the information contained herein as a springboard from which they can 1) continue their research on VBAC, 2) maintain a communicative relationship with their care providers, and 3) find a care provider who best supports the mother's interests and plans for the birth of her child.

Scare tactic: Baby is too large. Based on this recent sonogram, your baby is getting way too big for a vaginal birth, especially a VBAC. You can't safely have a VBAC with a macrosomic baby. We're going to need to schedule a repeat cesarean as soon as possible.

Questions to ask your care provider:
• How accurate are sonograms at predicting fetal size, particularly at the end of a pregnancy?
• What special concerns do you have when it comes to a woman birthing a big baby?
• Does fetal macrosomia increase the risk of uterine rupture?
• What does ACOG recommend when it comes to fetal macrosomia and VBAC?

A More Nuanced Analysis:

When a physician or midwife uses terms like "suspected fetal macrosomia" or "LGA" or "large for gestational age" in reference to your baby, what s/he means is that your baby's estimated weight has exceeded a particular cut-off point: typically, either 4000 g (or 8 lbs 13 oz) or 4500 g (or 9 lbs 15 oz).

The reasons for denying women the opportunity to plan a VBAC with a suspected macrosomic baby may vary. Some care providers might think that this increases the risk of uterine rupture. Others might want to forego the slightly increased risks associated with fetal macrosomia. And many might regularly schedule cesarean sections for all suspected macrosomic babies, whether or not their mothers have scarred uteri.

And, to be fair, there are some increased risks associated with fetal macrosomia, particularly if women have diabetes or uncontrolled gestational diabetes/gestational diabetes mellitus/GDM.

For one, fetal macrosomia is associated with a greater risk of shoulder dystocia, a labor complication that is serious but nearly impossible to predict, especially before labor even begins. Notably, the overall risk of shoulder dystocia during labor is approximately .6-1.4%. What's more, approximately one-half of all cases of shoulder dystocia occur with infants who weigh less than 4000 g -- that is, who are not macrosomic.

Fetal macrosomia is also associated with a greater risk of cesarean section, although this is likely related (among other things) to the relative immobility with which most women labor in hospitals, to the rising rates of labor induction, and to the fact that many care providers recommend prophylactic cesarean section for suspected fetal macrosomia. Worth noting is that labor induction -- which does slightly increase the risk of uterine rupture has not been found to improve labor outcomes for women and babies where the fetus is suspected to be large.

Nonetheless, barring any pregnancy complications that would greatly increase these and other risks associated with fetal macrosomia, the absolute risks themselves are quite low, and certainly not high enough to bar all women carrying fetuses who are suspected to be macrosomic from delivering those babies vaginally.

In this respect, it is exceedingly important to remember that any suspicions about fetal macrosomia are just that -- suspicions, estimates, educated guesses. In fact, weight estimates gleaned via ultrasound can be "off" by as much as one to two pounds! So even if ultrasound measurements determine that your baby is measuring 10 pounds, you might actually have an average-sized 8 pound baby (or, to be fair, a larger-than-average 12 pound baby). Thus, it is worth asking your care provider why this estimate by itself would disqualify you from planning a VBAC.

To this effect, your care provider might state that fetal macrosomia lowers the likelihood of a successful VBAC and that it increases the risk of uterine rupture. S/he might even mention the most current ACOG Practice Bulletin on VBAC, which does refer to some "limited evidence" showing a higher risk of uterine rupture associated with "women undergoing TOLAC [a trial of labor after cesarean] without a prior vaginal delivery and neonatal birth weights greater than 4,000g."

But this very excerpt from the ACOG Bulletin demonstrates that the issue is more complicated than simply claiming that "fetal macrosomia increases the risks of uterine rupture." For instance, while there is evidence suggesting that higher birth weights are associated with higher rates of uterine rupture, ACOG itself acknowledges that this evidence is limited. (The study I've linked to here examined 2586 women, but only 269 had babies with birth weights greater than 4000 g. This is a fairly small population, especially when one is considering using the study to disqualify women with suspected large babies from planning a VBAC.)

What's more, although a large baby may lower one's chance of having a successful VBAC, this does not mean that one has an absolutely low chance of having a VBAC with a large baby. In fact, in the aforementioned study, the VBAC success rate among women who birthed babies weighing over 4000 g was 62% -- not exactly a low success rate! And to be clear, the other 38% were simply those women who had cesarean sections following their VBAC attempts -- not necessarily those who had uterine ruptures following their VBAC attempts.

Finally, the current ACOG Practice Bulletin on VBAC also mentions the fact that most (if not all) of the studies examining VBAC success rates, uterine rupture rates, and fetal macrosomia used "actual birth weight as opposed to estimated fetal weight thus limiting the applicability of these data when making decisions regarding mode of delivery antenatally." In other words, the data used in these studies pertained to babies who were actually macrosomic -- not babies who were suspected to be macrosomic. It pertained to actual birth weights not to weight estimates. Thus, particularly since fetal weight estimates are notoriously inaccurate, it is questionable whether or not one can or even should apply these studies to any sort of prenatal counseling, especially counseling that dictates whether a woman should deliver her baby vaginally or via cesarean section.

In this respect, it is important to take note of ACOG's most recent recommendation on VBAC with suspected fetal macrosomia: "...it remains appropriate for health care providers and patients to consider past and predicted birth weights when making decisions regarding TOLAC, but suspected macrosomia alone should not preclude the possibility of TOLAC."

So if your care provider is denying you the opportunity to have a VBAC based only on suspected fetal macrosomia, you should definitely consider asking why s/he is departing from ACOG recommendations in this matter and/or what other reasons s/he has for barring you from a VBAC. You might also consider finding a more supportive care provider! Or just refuse an unnecessary cesarean, as it is your right to do!

What's more, you can always maximize your chances of a successful VBAC with a suspected large baby by walking, moving, and changing positions during labor and by avoiding giving birth on your back. The more you move and remain upright, the more you take advantage of gravity and of your pelvic flexibility and mobility to help bring your baby into the world. And suspicions about a large baby should not preclude you from doing just that.

Kristen Oganowski is a certified birth doula and PhD candidate in philosophy in Columbus, OH. She is the mother of two young children, one born via cesarean section and one born via VBAC. She also writes the blog Birthing Beautiful Ideas.

Copyright © Kristen Oganowski. Permission to republish granted to Pregnancy.org, LLC. Image credits: Benjamin Earwicke.