Cinderella VBACs and Gestational Age

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"At my last doctors appointment I went in and asked my doctor if I could continue with the pregnancy past 40 weeks if I were still pregnant. He said No because the risk of uterine rupture goes up past 40 weeks."  source

"Gestational age greater than 40 weeks alone should not preclude Trial of Labor After Cesarean." ACOG 

Many women planning a VBAC (Vaginal Birth After Cesarean) are told by their providers that they will be supported for a VBAC, but their doctors often conveniently forget to mention ahead of time that they enforce arbitrary rules that require women to go into labor by 40 weeks or be forced into a cesarean, like the woman quoted above. Some even insist on a repeat cesarean by 39 weeks.

This is what author Henci Goer calls a "Cinderella VBAC." The doctor claims to support VBACs, but puts so many limits on VBAC labors that almost no one gets one. Examples: the mother must go into labor before 40 weeks, the baby has to be below a certain weight, the mother must not gain very much weight in pregnancy, etc.

In that way, caregivers can give lip service to supporting VBACs without having to actually attend very many. As a result, activists separate caregivers into "VBAC Tolerant" versus truly "VBAC-friendly" by their insistence on these type of Cinderella VBAC restrictions.

Gestational Age Cutoffs in VBACs

One of the most common Cinderella VBAC rules is a gestational age cutoff. At 40 weeks, many women are told the risk for uterine rupture goes up so a VBAC labor would be too risky and they must schedule a repeat cesarean. However the research on uterine rupture past 40 or 41 weeks is conflicting and women are not being permitted to make fully informed decisions.

Some studies do show a modest increase in rupture risk by gestational age. However, others do not. One of the largest and most powerful gestational age studies did not show a statistically increased risk of rupture past the due date. This study was done at 17 different hospital centers, over a period of 5 years, and involved 11,587 women who labored for a VBAC.

What muddies the research waters is that many pregnancies after the due date end up induced, and a number of studies show that induction of VBACs is associated with more uterine rupture. So are the ruptures in these studies truly being caused by going beyond the due date, or is it an artifact of the high rate of inductions and augmentations done in pregnancies after 40 weeks? Some studies control for this and others do not.

In their book, Optimal Care in Childbirth (pg. 118), Henci Goer and Certified Nurse-Midwife Amy Romano note that the majority of uterine ruptures in these gestational age studies are found in the induced groups, and especially in those induced with an unfavorable cervix.

Now there is a new study just out on gestational age and rupture. It also found that the risk for uterine rupture did NOT increase with gestational age.

In this seven-year Israeli study of 2,849 women, 0.56% of women had a uterine rupture during a "trial of labor after cesarean" (TOLAC). The rate did not differ significantly by gestational age (GA), and  90% of women in the study had a VBAC. If all the women at 40 weeks had been forced to have a repeat cesarean, that would have been a lot of unnecessary cesareans. This study adds strong support to the position that women should not have to have a repeat cesarean at 40 weeks. The authors conclude:

Among women at term with a single previous cesarean delivery, GA at delivery was not found to be an independent risk factor for TOLAC success or uterine rupture. We suggest that GA by itself will not serve as an argument for or against TOLAC.

The latest guidelines from ACOG (the American College of Obstetricians and Gynecologists) note that gestational age beyond 40 weeks should not preclude laboring for a VBAC. This position is echoed by VBAC guidelines from other countries as well.

What About Inductions?

What about other options? To avoid going past 40-41 weeks yet still give the woman an opportunity at a VBAC, some caregivers will induce labor around the due date. They point out that in some studies the chance of a VBAC decreases after the due date so they hope that inducing at the due date gives the woman the best chance at a VBAC. They also point out that the risk for stillbirth, although quite low, does increase at some point after the due date.

However, induction at term has pros and cons. In most studies (but not all) induction of labor increases the risk for uterine rupture and decreases the chance of a VBAC. For example, the 2015 NICE guidelines from the Royal College of Obstetricians and Gynaecologists states:

Women should be informed of the two- to three-fold increased risk of uterine rupture and around 1.5-fold increased risk of caesarean delivery in induced and/or augmented labour compared with spontaneous VBAC labour.

In Optimal Care in Childbirth (pg. 118), Goer and Romano, noting that the majority of rupture cases that occurred after the due date were associated with induction, state:

These data suggest that women should not be induced for passing their due date. Induction both increases their risk of scar rupture and decreases the likelihood of VBAC. 

But how does induction of labor specifically compare with expectant management past the due date in VBAC women?  Recent research suggests that induction increases the risk for uterine rupture (1.4%) as opposed to expectant management (0.5%). In other words, caregivers' interventive management of women past the due date actually increased the risk for harm, not reduced it.

This is not to say that induction and augmentation should never be used in VBAC labors. Sometimes induction is medically necessary. Used carefully, induction and augmentation can be used safely in some VBAC labors. It doesn't have to be all or nothing.

Some types of VBAC inductions probably carry more risk than others, though. Some research suggests that prostaglandin use, sequential use of prostaglandins and pitocin, the induction of women with an unripe cervix, and the induction of women without a prior vaginal birth may raise the risk for uterine rupture.

For sure, misoprostol (PGE1) is associated with much higher uterine rupture rates and should never be used to induce a woman with a prior cesarean. The risk with other prostaglandins (PGE2) is less clear, though most clinicians avoid them these days.

Currently, the most favored method for inducing a VBAC is by mechanical means, such as amniotomy (breaking the waters) or a transcervical balloon catheter, along with oxytocin augmentation if needed. These methods may be less risky than other methods of induction for VBAC moms, although they still carry more risk for uterine rupture than spontaneous labor.

In other words, all induction scenarios do not carry equal risk. The risks may not be as high for induced labors in women with a very ripe cervix or with a prior vaginal birth, but parents should remember that the risk is never zero.

Although induction tends to lower the probability of having a VBAC, many women are induced and do have VBACs. This seems especially true for women with a high Bishop's Score (indicating a ripe cervix) or a previous vaginal birth. Regardless, the majority of women who have been induced do have VBACs. In several recent studies, about one-half to two-thirds of induced labors ended in VBAC. That's a lot of repeat cesareans averted.

Induction is a decision that should not be taken casually but which can be a legitimate choice for some. However, induction is generally overused in VBAC labors, and is often undertaken without fully apprising women of the risks associated with it. But it does remain a viable choice and there are women who have had induced VBACs.

Summary

When a woman with a prior cesarean passes her due date, there are many courses of action that are possible. Every choice has benefits and risks. Although the vast majority of women with a prior cesarean will have good outcomes whatever they choose, there are unique pros and cons to consider.

The most logical choice is to let nature take its course and wait for spontaneous labor. Many caregivers are very supportive of waiting for spontaneous labor after 40 weeks in women with a prior cesarean, and many will wait until after 41 weeks or even later to start discussing alternatives, as long as mother and baby are doing well. Obviously, each case's unique circumstances must be considered.

On the other hand, a surprising number of caregivers still use gestational age restrictions and force either repeat cesarean or induction at 40 weeks. For some, this is out of fear of any possibility of increased risk of rupture or a fear of stillbirth. For others, it is out of a mistaken belief that after 40 weeks, there is little chance of a VBAC. A cynic would also note that since about half of women do not go into labor before their due date, gestational age restrictions also mean that doctors attend fewer VBAC labors, easing their schedules while still letting them appear to be supportive of VBACs.

Unfortunately, research does not offer 100% clear guidance on uterine rupture risk after 40 weeks. Some research suggests a somewhat increased risk, but a closer look suggests the risk is mostly in induced labors or the difference is quite modest. The strongest research does not show an increased risk after the due date at all.

Gestational age restrictions also bring up the question of ethics. Mandating a repeat cesarean or an induction at a certain gestational age is a high-handed and paternalistic approach. It infantalizes women and strips them of their autonomy to make their own medical decisions. It also ignores the possible harms associated with these interventions.

Instead, women should be counseled about the pros and cons of each choice. Caregivers may advise a certain course of action, but in the end the woman has the right to accept or refuse that course of action. Discussion of these issues should begin early in pregnancy, not at term, so there is plenty of time for decision-making. Remember, every choice has pros and cons.

Repeat Cesarean without labor

Pros: Convenience of scheduling; lowest risk for rupture; no uncertainty of labor
Cons: All the risks of surgery and surgical recovery (bleeding, pain, infection, blood clots); more breathing problems for the baby; more breastfeeding problems; substantial risk of life-threatening placental issues in future pregnancies

Expectant Management past due date

Pros: Spontaneous labor is usually easier/less painful and VBAC is more likely; baby is more ready for life outside the womb (less problems with breathing, breastfeeding, blood sugar levels, bilirubin levels); mother usually has an easier recovery
Cons: May labor and still end up with a cesarean; continuing the pregnancy entails the very small but real risk of stillbirth or uterine rupture; may still need to have induction of labor at some point, may have decreased chance of a VBAC (although this may be influenced by high induction rates later)

Induction of Labor at 40 or 41 weeks

Pros: Induction can be scheduled and planned for; most of the time induction still ends in a VBAC; induction means predictable staffing requirements for the hospital
Cons: Induction involves a harder labor and more need for pain relief; more risk for fetal distress; a significantly increased risk for uterine rupture; and typically a decreased chance for a VBAC. May still end up with another cesarean after labor

Clearly, there are no easy answers. No one answer is the right answer for all women and situations.

The most important take away here is that after the due date, women with a prior cesarean should not be forced into anything; they should have choices. The pros and cons of the various choices should be reviewed with the mother and the ultimate choice should be left up to her. 

At term, some women will choose repeat cesarean, some will choose induction, and some will choose to wait for spontaneous labor. All are valid choices.

The ACOG guidelines are clear and caregivers need to honor them. Gestational age past 40 weeks should not be used as a cut-off to keep women from laboring for a VBAC.

Women who want a VBAC should ask careful questions early in pregnancy about the guidelines of their providers, including whether there are gestational age cutoffs or other limitations on their options. Be proactive; don't wait until the last minute to find out. In some cases, women may need to switch providers in order to get a truly VBAC-friendly provider. It is possible to do so, even late in pregnancy, but the process is easiest when it's done early.

The time is at hand. All women deserve to go to the ball if they want to. "Cinderella VBACs" need to become a thing of the past.

Checklist originally from Melek Speros

References

Arch Gynecol Obstet. 2018 Jan 22. doi: 10.1007/s00404-018-4677-9. [Epub ahead of print] Trial of labor following one previous cesarean delivery: the effect of gestational age. Ram M, Hiersch L, Ashwal E, Nassie D, Lavie A, Yogev Y, Aviram A. PMID: 29356955

PURPOSE: To stratify maternal and neonatal outcomes of trials of labor after previous cesarean delivery (TOLAC) by gestational age. METHODS: Retrospective cohort study of all singleton pregnancies with one previous cesarean delivery in TOLAC at term between 2007 and 2014. We compared outcomes of delivery at an index gestational week, with outcomes of women who remained undelivered at this index gestational week (ongoing pregnancy). Odds ratios and 95% confidence intervals were adjusted for maternal age, previous vaginal delivery, induction of labor, epidural use, presence of meconium, and birth weight > 4000 g. RESULTS: Overall, 2849 women were eligible for analysis. Of those, 2584 (90.7%) had a successful TOLAC and 16 women (0.56%) had uterine rupture. Those rates did not differ significantly for any gestational age (GA) group. Following adjustment for possible confounders, GA was not found to be independently associated with adverse maternal or neonatal outcomes. CONCLUSION: Among women at term with a single previous cesarean delivery, GA at delivery was not found to be an independent risk factor for TOLAC success or uterine rupture. We suggest that GA by itself will not serve as an argument for or against TOLAC.

Obstet Gynecol. 2005 Oct;106(4):700-6. Safety and efficacy of vaginal birth after cesarean attempts at or beyond 40 weeks of gestation. Coassolo KM, Stamilio DM, Paré E, Peipert JF, Stevens E, Nelson DB, Macones GA. PMID: 16199624 

OBJECTIVE: To compare rates of vaginal birth after cesarean (VBAC) failure and major complications in women attempting VBAC before and after the estimated date of delivery (EDD) METHODS: This was a 5-year retrospective cohort study in 17 university and community hospitals of women with at least 1 prior cesarean delivery. Women who attempted VBAC before the EDD were compared with those at or beyond 40 weeks of gestation. Logistic regression analyses were performed to assess the relationship between delivery beyond the EDD and VBAC failure or complication rate. RESULTS: A total of 11,587 women in the cohort attempted VBAC. Women past 40 weeks of gestation were more likely to have a failed VBAC. After controlling for confounders, the increased risk of a failed VBAC beyond 40 weeks remained significant (31.3% compared with 22.2%, odds ratio 1.36, 95% confidence interval 1.24-1.50). The risk of uterine rupture (1.1% compared with 1.0%) or overall morbidity (2.7% compared with 2.1%) was not significantly increased in the women attempting VBAC beyond the EDD. When the cohort was defined as 41 weeks or more of gestation, the risk of a failed VBAC was again significantly increased (35.4% compared with 24.3%, odds ratio 1.35, 95% confidence interval 1.20-1.53), but the risk of uterine rupture or overall morbidity was not increased. CONCLUSION: Women beyond 40 weeks of gestation can safely attempt VBAC, although the risk of VBAC failure is increased.

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