Late one night (I think about things late at night or in the shower…probably has something to do with the kids not being around!) I got to thinking about some of the scenarios that I’ve seen play out over and over. And some of the nonsensical things I’ve been told Obstetricians say. So I got to thinking about the things that scare Obstetricians. This is what I came up with.
What is the specific risk of concern? Uterine rupture. Trying to figure out "risk factors" for uterine rupture in VBAC has been the subject of an enormous amount of research. We do know this: macrosomia and postdates are not associated in and of themselves with an increased risk of rupture (management of these pregnancies is another matter).
We also know that induction, of all types, is associated with an increased risk of rupture -- the actual numbers vary quite a bit, and which agent you are induced with matters too, but it is pretty much accepted that induction increases the risk "some amount" (which is not to say that its a universally unacceptable risk, it may be a valid consideration in some cases, but it is a true risk). Pretty much we don't know anything else -- obviously, there are a few women that do have a rupture and aren't induced but we don't know why, and it is important to understand that this is a very rare event. And basically unpredictable. Which humans hate. So, we try to come up with reasons to explain it and make it predictable and hence avoidable. At any rate, unpredictable, rare and possibly catastrophic events make obstetricians very scared. I could go on about how they are responsible for setting up a system where they now have to be scared of this but that’s another essay.
Macrosomia means very large babies, nearing 10 pounds and over. Shoulder dystocia means the baby's head is out, but baby is stuck at the shoulders.
What is the specific risk of concern of macrosomia? Shoulder dystocia. Shoulder dystocia is seen proportionally more often in larger babies, though approximately 50% of all shoulder dystocia occurs in babies of "normal" weight. It is also unpredictable. It can be nothing more than really scary, with lower APGARs than anyone likes to see, or there can be transient nerve damage to the arm or there can be permanent nerve damage or very very rarely, a baby can die (I might add, all of these do occur during c-sections to prevent shoulder dystocia as well, so that isn't even completely protective!). I repeat, it is unpredictable and guess what? Scared obstetricians, that's what. Interestingly enough, it is also one of the most common reasons obstetricians get sued, to a degree out of proportion to the actual number of shoulder dystocias that occur. Certainly this is in part due to the belief that “if the obstetrician had ‘just’ done a cesarean, none of this would have happened”. Because the obstetrician should “know better”. The fact that the obstetricians have created this misplaced trust is that other essay…
Shoulder dystocia is made more likely and more severe by a number of the "standard" protocols that go with a hospital birth -- for one, it is well established that vacuum extraction/forceps use significantly increases the chance of a shoulder dystocia. Laying on your back or sitting back on your tail bone during pushing reduces your pelvic opening (as much as 30%) so this also increases the risk. Drugs (like an epidural) that interfere with your body's ability to push probably create a riskier situation. Augmenting contractions (pitocin) during pushing has the potential to increase risk too- same general idea as vacuum extraction, if you force a baby into the pelvis too quickly, the natural loosening and stretching of the pelvis may not occur.
I believe that valsalva or "purple pushing" (forced to push) is probably a risk factor. A big baby needs time to mold and move -- patience and a hands-off attitude are very, very important. It is eye-opening to read how midwives (vs. obstetricians or medwives) view big babies – most midwives I know like big babies because they actually make for more straight forward labors as long as the mother is upright and mobile. This is completely differently from the fear-based medical model of care.
Sometimes shoulder dystocia occurs, even when everything is done "right" -- it is a real phenomenon but, and I believe this with all my heart, I think most shoulder dystocia (in N. America) is iatrogenic -- caused by the actions of the attendant, not something that was "fated" to occur. It seems to me that homebirth midwives don't see nearly the same number of shoulder dystocias nor do they have the same degree of disastrous outcomes as the hospital-based caregiver -- in my opinion that says something profound about "management". Note that none of this has anything to do with VBAC or rupture, with the exception that early induction is often recommended for a suspected big baby (prediction of big babies is a chancy thing – late term size estimation via ultrasound is known to be notoriously inaccurate) -- and we know that's an increased risk for rupture.
What are the specific “risks” of concern about post-dates? There are two, and growing a big baby is one of them. I’ve already covered the fears about macrosomia. The other “risk” is a condition called "post-maturity". This is a situation where it seems that the baby has actually "been inside too long" -- there are some very specific characteristics associated with post-maturity and it is very important to understand that this too is a rare condition -- it is usually associated with babies that are past 42 weeks, but is also seen in babies that aren't even "term" yet -- so it isn't as simple as "you've been pregnant too long".
Basically, many babies are "post-dates" (if you consider anything after 40 weeks "post-dates" then most babies are post-dates, because 75-85% of all babies are born after 40 weeks, if left to their own devices -- 41 weeks is a more accurate "average" length of human gestation) but very few are "post-mature". There are tests that can be done to try to predict which babies are at risk for post-maturity, like the biophysical profile and non-stress test, and sometimes these tests do seem to show something. But a lot of the time, these tests give a "false positive" meaning that they show a problem but there really isn't a problem -- the tests are pretty controversial in some circles. I had a conversation with a well-known “high risk” obstetrician in my area and he said that about 50% of the time, these tests give a false positive. He also said that even knowing that, if the test showed a possible problem, he was obligated to “do something”. I think this is crazy but I did appreciate his honesty. Of course, I wasn’t pregnant and under his care, so he had little to lose in admitting this to me.
There has been quite a bit of research on the "increase" in mortality as babies go beyond 42 weeks but the study designs have been flawed and the data is very old (from the 1950’s in several cases, a sample group which has almost nothing in common with women today) so my opinion is that there really isn't good evidence to say that anything past 42 weeks is significantly riskier to the baby. Once again, you can see that this has nothing to do with VBAC and rupture -- with the same exception as above -- get to 42 weeks with a hospital-based caregiver and you are going to find it extremely difficult to avoid an induction and that is a problem for a VBAC.
If you are interested in launching into learning more about macrosomia and post-dates, you might start with Henci Goer's book "The Thinking Woman's Guide to a Better Birth". You can also start reading at the Gentlebirth site. You'll get a variety of viewpoints (including the obstetrical view), though most of the information is from the midwife viewpoint.
As a generalization, the obstetrical/medical model of care is a fear-based philosophy (yes, there are obstetricians that don't buy into it, but most do). VBAC, macrosomia and post-dates each present the rare possibility of a serious or catastrophic complication. The fact that many of the routine interventions associated with obstetrical care actually make those complications more likely goes unnoticed, of course (or at least no one talks about it). Obstetricians are surgeons trained in the pathology of the female reproductive tract so that's what they are looking for and that's usually what they find, whether it actually exists or not.
Most women do not realize that obstetrics is also one of the least evidence-based specialties there is. For example - why else do a significant number of women having their first baby still get episiotomies when the research is unequivocal that episiotomies are damaging and serve no purpose for either the safety of the mother or the baby? Because that's the way it’s always been done! Why are most labors monitored with continuous electronic fetal monitoring, even though there is unequivocal evidence that continuous monitoring does not improve outcomes at all, and only contributes to a higher cesarean rate? Because we’ve been doing it for so long, we must keep doing it!
VBAC, macrosomia and post-dates are "hot-beds" of non-evidence based practice. Hence the importance of learning about this stuff yourself – how you will be treated during your pregnancy and labor is more about belief system than scientific fact and you must understand the belief system your caregiver is operating under. In order to understand the different belief systems, you need to know the facts first, so that you don’t confuse habit of practice with best practice.
Given how many women end up with cesareans because of failed inductions because they had a “big baby” or were “past due”, the likelihood that a woman desiring a VBAC will also be dealing with one or either of these circumstances is high. The problem is, if you are someone who has had a previous cesarean, who grows big babies, who goes beyond 40 weeks (or heaven forbid, 42) you have 3 separate "scary scenarios"; the risk associated with a VBAC isn’t changed one whit by the other concerns. Any one of those three is enough to throw most obstetricians (and some "midwives") into a real tail-spin -- try to do all three with some and you are way beyond their comfort level. When a surgeon is challenged, surgery is the fastest means to feeling safe again. Be prepared, so you know what you might have to deal with – it is best to find someone early on (best before you are pregnant) who doesn't have these fears. And once again, that's a whole ‘nuther essay!
revised June 11, 2006