Several weeks ago I wrote about the one size fits all approach of homebirth midwives. No matter the question, the answer is always homebirth.
Natural childbirth advocates have a one size fits all approach, too:
Personal characteristics are irrelevant. Advanced maternal age, maternal obesity, pre-existing maternal disease? It doesn’t matter because the counseling and treatment plan are always the same: you can and should have an unmedicated vaginal birth.
Medical history is irrelevant. Had a previous shoulder dystocia, C-section, postpartum hemorrhage? Who care? You can and should have an unmedicated vaginal birth.
Complications are irrelevant. Baby is breech, have gestational diabetes, colonized by group B strep? Who cares? You can and should have an unmedicated vaginal birth.
Labor complications are irrelevant. Dysfunctional labor, prolonged rupture of membranes, pushing for 4 hours? Who cares? You should still stay home because you can and should have an unmedicated vaginal birth.
In my piece about homebirth midwives, I ascribed this one size fits all approach to ignorance and dogma, and that goes for natural childbirth advocates as well. Ignorance refers not only to obstetrics, but also to basic statistics. One facet of this ignorance is the mistaken belief that statistics for a group as a whole apply equally to each individual.
Take the case of VBAC (vaginal birth after Cesarean). The overall success rate for attempted VBAC is nearly 76%. Natural childbirth advocates think that means that each individual woman’s chance of a successful VBAC is also nearly 76%. Nothing could be further from the truth. Both the chance of having a successful VBAC and the chance of a uterine rupture are modified by past medical history and factors in the current pregnancy. That was the take home message of the lecture on VBAC that I attended at the recent Harvard Medical School Review of Obstetrics .
History of a previous vaginal birth impacts the chances of successful VBAC Women who have had a previous vaginal delivery (VD) have an 86% chance of successful VBAC, and women who have had a successful VBAC in a previous pregnancy have a nearly 90% chance of having another. But for women who have never had a VD, the chance of successful VBAC is only 61%.
The reason for a previous C-section also impacts the success rate of attempted VBAC If the previous C-section was done for a non-recurring condition like breech, the chances of successful VBAC are higher than for women whose previous C-section was performed for dystocia.
The larger the baby, the lower the chance of successful VBAC Although macrosomia (baby larger than 4000 gm) in the absence of other risk factors is not an indication for repeat C-section, the size of the baby definitely affects the chance of success. For example, while a woman who had a previous C-section and no vaginal deliveries has an overall chance of successful VBAC in the range of 60+%, the chance of success drops to 38% if the baby is over 4500 gm. And if the previous C-section was done because the baby didn’t fit, the chance of a successful VBAC with a baby over 4500 gm is only 29%.
Other factors also have a large impact on success For example, if the baby’s head has not descended into the pelvis at the start of labor, the chance of successful VBAC drops to only 10%.
Maternal factors affect success The chance of successful VBAC drops as maternal age increases, and as maternal BMI (body mass index) increases. Women over age 35 and women with a BMI greater than 30 have a lower chance of successful VBAC.
The most dreaded complication of attempting a VBAC is rupture of the uterus, leading to massive hemorrhage, death of the baby and possible death of the mother. The risk of rupture also depends on the circumstances surrounding the previous C-section and characteristics of mother and baby in the current pregnancy.
Overall, elective repeat C-section is safer for the baby, and vaginal delivery is safer for the mother But those risks are not equal. The risk of death of the baby in attempted VBAC is 10X than the risk of death of the mother from a repeat C-section.
The worst situation for both mother and baby is a failed attempt at VBAC. While the overall risk of uterine rupture is 7/1000, that jumps to 23/1000 in a failed attempt. Therefore, the risk of rupture is directly dependent on the chance of success.
Other factors also affect the risk of rupture These include the type of incision on the uterus (transverse is safer than vertical), the length of time since the last pregnancy (an inter-pregnancy interval of less than 6 months triples the risk of rupture), and the timing of the previous C-section (a preterm C-section has a higher risk of rupture in a subsequent pregnancy than a term C-section).
The bottom line is that an individual woman’s chance for a successful VBAC and risk of a uterine rupture depend on her specific circumstances.
Should a woman try for a VBAC?
Natural childbirth advocates, who take a one size fits all approach to everything, will counsel every woman to attempt a VBAC and quote an overall risk of success that may not actually apply to that woman.
In contrast, obstetricians, who provide care customized to the individual woman, can offer her a realistic assessment of her chances of a successful VBAC, and a realistic assessment of the risk of a uterine rupture. Ultimately, of course, each woman has to decide for herself which risks she is willing to take, but she can only make an informed decision if she has all the information. The one size fits all approach does not allow her to make an informed decision.
Only a personalized risk assessment, based on HER history, HER medical conditions, and the size and position of HER baby will allow her to make an informed choice for VBAC or elective repeat C-section.