[Music] Hi, I'm Anne Walfield, I'm Karl Lepicarara, and I'm Mel A. Kemen, and we're your hosts of the Uterine Sound Podcast, bringing you up to date information in all things ONG. Over the past few weeks, we've been talking all about Caesarian sections, so it seems only fitting that this week we discuss V-Back, otherwise known as the V-Janal Birth after Caesarian section. After a woman has a Caesarian section, she has a choice about how she wants to deliver her next baby, a collective repeat Caesarian section, or try for a V-Back. Both options have pros and cons, and our job is to help provide information and support the woman in whatever choice she makes. So why is this even an issue? Why do we need to have a discussion about V-Back at all? I mean, shouldn't have a Janal Birth after a Caesarian section be a standard option? The main reason we need to talk about V-Back is because of the possibility of Uterine rupture. Now this complication is rare, but it can have significant implications for the mother and baby, which is why we need to have a conversation about it. Uterine rupture cares whether it's disruption of the Uterine muscles, extending through the Uterine serrosa, or extending into the bladder or broad ligament. This is slightly different to uterine dehycens, which is disruption of the Uterine muscle with intact Uterine serrosa. Now, Uterine ruptures can happen in any pregnancy, even if you haven't had a Caesarian before, with an incidence of 0.5 to 2 per 100,000 pregnancies. But the risk of Uterine ruptures increased in women who have had a previous Caesarian section. Ranskelk quotes the rate of Uterine rupture as 5 to 7 per 1000 attempts at V-Back, which is about 1 in 200. That rate rises to about 1 in 80 to 1 in 100 with the use of oxytocin. The frequency of Uterine ruptures further increased, depending on the type of Uterine incision. The current Ranskelk guideline quotes a Uterine rupture risk of 2 to 9 per cent with previous classical Caesarian, 2 per cent with inverted T or J incisions, and 2 per cent with a low vertical incision. Okay, so I understand the mechanism of a Uterine rupture after a Caesar. You've essentially got a weak spot on the Uteris, which can rupture under tension, like with a contraction. But I didn't realise you could rupture without a Uterine scar. Who else is at risk of a Uterine rupture? The Uterine rupture can happen in any pregnancy, but there are a few at-risk groups, aside from those women who've had a previous Caesarian section. These include grandmelties, and multipleous women with obstructive labour and use of oxytocin, women with acyclage who present in labour, and those with previous Maya-Meetural surgery. Ah, okay. I always wondered why we use caution when using oxytocin in multis, and why it's important to exclude obstructive labour before doing so. One of my colleagues was saying the other day that all of the Uterine ruptures that they've seen have been in multis with obstructive labour on oxytocin. If a Uterine rupture does occur, what kind of outcomes are we looking at for mum and baby? Uterine ruptures can be devastating for both mothers and their babies. If a Uterine rupture does occur, there's a one-in-seven chance of neonatal death or severe neonatal hypoxia, and a significant risk of the mother needing a hysterectomy. There is also a risk of significant blood loss requiring transfusion, genitoriuminary injury, and perinatal or maternal death. And when do most Uterine ruptures occur? Do they always happen in labour? Most Uterine ruptures, more than 90%, occur during labour, with a peak incidence at 4 to 5 centimetres dilatation. 18% occur on the second stage, and 8% are identified after delivery, usually in the workup of a PPH. But it's important to remember that a Uterine rupture can actually occur at any time during the pregnancy, although it's much less likely in the absence of Uterine activity. I guess that's why we like women to come in early in labour when they're having a V-back. If most ruptures happen in early labour, then we really want the woman to be somewhere where it can be detected and managed quickly, rather than laboring at home. And don't forget Uterine rupture in your differential diagnosis when you're thinking about your 4Ts in a PPH. Uterine rupture would fall under the T for trauma. So how do we recognise if a Uterine rupture is happening? The most common feature is an abnormal CTG, which occurs in 55 to 85% of women with Uterine rupture. This would usually present a sudden onset of complicated or variable or late decelerations or a fetal bradycardia. We would also be suspicious if there were severe abdominal pain persisting between contractions, particularly if that pain is right over the previous Caesar scar. Other signs include cessation or alteration of Uterine activity, abnormal vaginal bleeding or hematuria, loss of station of the presenting part, change in abdominal contour, chest pain, shoulder tip pain or sudden onset of shortness of breath, and maternal tachycardia, hypertension, shock or fainting. And if we suspect a Uterine rupture, though we obviously need an immediately cat-one laparotomy to deliver the baby as soon as possible and to repair any damage that has occurred to the Uteris or surrounding structures. The damage can sometimes be quite extensive involving the bladder or the posterior Uteris. The reason I'm saying a laparotomy in not a Caesarian section is because if the Uteris is already ruptured, then you actually don't need to make a Uterine incision. The baby is usually already delivered or partially delivered into the abdominal cavity. Although I definitely still call it a cat-one Caesar, so that theatre does a right set-up when and we're not confusing anyone. Okay, so to summarize what we've learned so far, a Uterine rupture is a full thickness rupture of the myometrium and serosa, or extension into the bladder and broad ligament. It's most common after a Caesar, but it can happen with any pregnancy. The risk of Uterine rupture is about one in two hundred after one Caesarian section. This increases to one in eighty with the use of oxytocin and one in fifty with a classical Caesarian section. Other women at risk of Uterine rupture include granmoltes, multis with obstructed labor and cento, women with a seclarion labor, and those with a previous myometri. Uterine rupture most commonly occurs at four to five centimeters, but can also happen before or after labor. Signs of Uterine rupture include an abnormal CTG, Caesar scar pain between contractions, cessation of Uterine activity, abnormal vaginal bleeding, hematuria, chest or shoulder tip pain, maternal hemodynamic shock, and loss of station of the presenting part. And if we detect a Uterine rupture, we need to call a cut one Caesarian section. Okay, so we've spoken a lot about Uterine rupture, but it's important to remember that the vast majority of women who have a V-back actually won't have a Uterine rupture. Roughly 99.5% of women trying for a V-back will not rupture their Uteris. However, if you are in that minority of women who do have a Uterine rupture as a complication, it is a massive deal, which is why we need to talk about it. Do we know how many women are actually choosing to have a V-back versus an elective Caesarian section? The latest data from the AIHW from 2021 shows that 12% of women who've had a Caesarian section for their first baby will have a vaginal birth for their second baby. An 88% will deliver by a Caesarian section. Unfortunately, this data doesn't tell us how many women are choosing to trial a V-back. So if you care, Victoria reports that up to 58% of women with one previous Caesarian section will attempt a V-back. These stats are very different in different countries, with up to 80% of those from the US choosing to have a repeat elective Caesar. And obviously, the numbers are likely to vary in different hospitals and different demographics. There's a famous quote in the literature, "Once a Caesar always a Caesar," and certainly the V-back rates in the early 1900s reflected this with the V-back rate of only 3%. But we've moved away from that a lot in recent years as a safety of V-back is becoming more and more established. In fact, V-back attempts climbed initially in the 1990s to 40% to 50% and then dropped to 10% in the early 2000, as guidelines became more cautious about the risk of uterine rupture. Nowadays, V-back is recognized as a safe and reasonable birth choice for most women, and so the V-back rates of V-back are again rising. And if a woman does choose to have a trial of labor after Caesar, how likely is she to actually go on to have a successful V-back? Again, success rates vary widely, but the most commonly quoted statistic is a success rate of 60 to 80%. Of those women who choose to a trial of labor after Caesar, 60 to 80% will have a successful vaginal birth, which means that 20 to 40% will go on to have an emergency cesarean section. Now, this might sound like a low success rate, but when you consider that the incidence of cesarean section in primips is about 35%, then the V-back success rate is actually quite similar to the success rate for the genal birth in primips. Now, this is a statistic quoted in the green top guidelines and the red core guidelines. However, an Australian study suggests that the V-back success rate in Australia may be closer to 56%. It's important that hospitals know their own V-back success rates in order to provide local data to their patient population. And is there any way we can predict who might be more likely to have a successful V-back? There's no way to be 100% sure about who will have a successful V-back and who won't. But there are some factors that are associated with the higher chance of success, and some factors that are associated with the higher chance of an eating and emergency cesarean. So first, factors that increase the chance of a successful V-back [BLANK_AUDIO]
include previous safe vaginal birth, previous successful fever, spontaneous onset of labor, age under 40, BMI under 30, gestation under 40 weeks, estimated feet away under 4 kilos, and an uncomplicated pregnancy without other risk factors. Previous vaginal birth, especially successful feedback, is the strongest predictor of success, and the V-back rates of 87 to 91% reported in that group. Factors that decrease the chances of a successful V-back include age over 40, BMI greater than 30, gestation over 41 weeks, short stature, fetal malpresentation, more than one previous cesarean section, a previous cesarean section for dystocia, induction of labor, fetal malchromyocrysomia greater than 4 kilos, and diabetes or hypertensive disorders. In fact, if you have a combination of a BMI greater than 30, a previous cesarean for dystocia, no previous vaginal births, and you have an induction, your chances of a successful V-back are only about 40%. Also, if you just have a BMI greater than 40, then your success rate is only about 60%. Ooh, and there is a V-back calculator available online that can help calculate a woman's individual chances of having a successful V-back. It uses parameters like maternal age, BMI, previous vaginal deliveries, previous V-back, and indication for previous Caesar, as well as the presence of chronic hypertension. It's quite easy to use, and it can be helpful with counseling. It's based off data derived from the maternal fetal medicine unit cesarean registry, which included over 11,000 women, and apparently has been validated. It is also an Australian-based V-back calculator, which was derived from 22,000 women, and is available at vbaccalculator.com. It's also important to talk about contraindications to V-back. There are certainly some circumstances where the risk of rupture is significantly increased, and in these situations we would strongly advise against a V-back. Controindications to V-back include a previous uterine rupture. These women have a greater than 5% risk of recurrence, or put another way, or one in 20 chance of another uterine rupture. A previous classical caesarian, remember the rights of uterine rupture in this group are coited between 2 to 10%. Any of the uterine ruptures I've seen pre-labor have all been in women who've had previous classical caesarians. Where there's already other contraindications to have vaginal birth, for example, malpresentation or placenta-previous, and previous mymectomy involving the uterine cavity or extensive mymeasured section. You should also exercise caution with previous inverted T or J-Insigen, low vertical uterine Sigen, significant inadvertent uterine extension, and women who've had three or more previous cesarian sections. OK, so how do we actually put this into practice? Let's say I'm in the anti-natal clinic and I'm asked to see Larissa. Larissa is a G2P1 at 32 weeks gestation, and she's had one previous caesarian section. She wants to consider a view back for this pregnancy, but she'd like to know some more information. How do we approach this consultation? Well, firstly we want to explore Larissa's circumstances and particularly have a look at her birth records for her previous pregnancy. What was the indication for the first caesarian? As we mentioned before, if the caesar was for fetal distress, then Larissa is much more likely to have a successful birth than if the caesar was for dystocia. What happened in the operation? Was it a straightforward lower segment caesarian section? Or did she need a classical caesarian or an inverted T or J, which would significantly increase the risk of uterine rupture? And how long ago was the caesar? Ideally we want an interdelivery interval of 18 months. An interprognancy interval, which is the time of caesarian section, to conception of the next pregnancy, of less than 12 months is associated with an increased risk of uterine rupture, placenta-previa, placenta-lubruption and preterm birth. A short interprognancy interval is not in itself a contraindication to V back, but women need to be informed of the increased risk of uterine rupture. Next we need to review this current pregnancy. Where is the placenta? It's a placenta with anterior and low interpatient with a previous caesar, though we need to be attuned to the possibility of placenta-creator. If we suspect this, then we should arrange for further imaging, typically an MFM ultrasound or even an MRI. We also need some basic details like age, BMI, any pregnancy complications and an estimated fetal weight if available. Now just note we don't routinely arrange growth scans just because someone's considering a V back. But if she's having a scan for another reason, then the information can be useful. For example, if she's had an emergency cesare for labor distortion in the previous pregnancy, then if the estimated fetal weight of this baby is larger than the first baby, her chances of a successful V back are going to be reduced. For patients with no previous vaginal birth and an estimated fetal weight of 4 kilos, the success rate of V back drops to less than 50% and the risk of uterine ruptures also increased. Okay, so we've explored the current pregnancy. Located the birth records for the previous pregnancy, made sure the placenta is clear and excluded any contraindications to V back. With that information, we should be able to calculate the chances of a successful V back and discuss that with our patient. Now we need to have a chat about the risks and benefits of a trial of labor after Caesar versus the risks and benefits of an elective Caesar. It's important to present all of the information so Larissa can make an informed choice. Let's start with V back. Based with everything in obstetrics, we can divide these up into maternal benefits and neonatal benefits. The maternal benefits of a trial of V back include a 60 to 80% success rate of having a vaginal birth, less maternal morbidity for this and future pregnancies, avoidance of major surgery and the need for multiple caesareans in future pregnancies, remember one successful V back increases the likelihood of future vaginal births, earlier mobilization, shorter length of stay and shorter recovery and higher patient satisfaction if their goal is to achieve a vaginal birth and also reduced rates of DBT. The benefits for the baby include improved gut microbiota, which is linked with reduced risk of allergies, reduced transient respiratory morbidity and increased maternal fetal bonding. Now let's discuss the risks. Remember there are pros and cons to everything. The maternal risk of V back include uteroin rupture, like we've already said, typically quoted at a rate of 1 in 200 or 5 to 7 in a thousand. If a uteroin rupture occurs there's a 1 in 7 chance of a neonatal death, severe hypoxia or of mum requiring a hysterectomy. A 20 to 40% risk of an emergency caesare, which carries a high rate of complications than an elective caesare, and then there's the general risks of vaginal birth. Like a pelvic floor trauma, 5% risk of oasis, risk of instrumental, sorry, that was if this is a first for general birth and risk of instrumental delivery, about 40%. The fetal risk of V back include an increased risk of stillbirth compared to elective caesare at 39 weeks, 1.8 in a thousand pregnancies. Now this is mainly due to a background increased risk of stillbirth after 39 reeks, justation, rather than actually just people having a V back. The remainder of the fetal risks of V back are typically related to uteroin rupture, so these include intratratum death or neonatal death, 0.25% increased risk of perinatal mortality, 0.08% risk of HIE, which is hypoxic ischemic in kephalopathy, and of course there are the general risks to the baby of a vaginal birth, including fetal trauma, shoulder to toe-shab, like brachial plexus injury and fracture. So obviously we have to compare the risks and benefits of a V back to the risks and benefits of an elective repeat caesare at 39 weeks. Again, these can be divided into maternal and fetal risks and benefits. The maternal benefits of an elective caesare include reduced maternal risks associated with emergency caesare, it avoids perennial trauma and associated urinary problems, the convenience of a planed date of birth, reduced risk of scar rupture, and the option for triple lagation of fertility is not desired. Fatal benefits include avoiding late stillbirth, and as Anne said, this is purely because the rate of stillbirth is lowest at 39 weeks gestation, not because the cether itself lowers the risk of stillbirth, and remembering that that risk is still incredibly low at 1.8 per thousand. Reduced perinatal morbidity and mortality from HIE related to labor, delivery and scar rupture, and reduced risk of traumatic fetal injury from birth. The risk of fetal injury at elective caesare in section is 5,000 and 1,000, with the majority over 71% being just a superficial skin laceration. The risk of fetal intercranial injury is also lowest at caesare in section, as is the risk of brachial plexus injury from shoulder to stoksia. And the maternal risks. Longer recovery and length of stay in hospital, recommendation for repeat caesare in the future, an increased risk of placenta, prior and accretar and subsequent pregnancies which may require a caesare in hysterectomy, surgical complications including bleeding, infection, hysterectomy, an increased risk of complications and subsequent pregnancies. The fetal risks include low rates of initiating breastfeeding, fetal injury of 1 in 200, again, mostly superficial and an increased risk of TTN, succinctant to fish.
impolinary hypertension, although after 40 weeks there's no difference in this incidence. Now obviously this is a lot of information to take in. It can be really helpful to provide women with a written information leaflet, which outlines the risks and benefits of both elective Caesar and V-back. It's also important to have this discussion in the context of the woman's individual circumstances, including her personal motivation and preferences for motive delivery, her attitudes towards the risks of rare but serious adverse outcomes, her plans for future pregnancies and her chances of a successful V-back. So back to Larissa. Larissa is given some written information on V-back vs. elective caesarian section, and she's had some time to consider her options and ask questions. She decides she wants to go ahead with a V-back or a trial of labor after Caesar. Tollack or trial of labor after Caesar is probably the more appropriate terminology, since we can't guarantee that a trial of labor after a Caesar will actually lead to a vaginal birth. Are there any special considerations we need to have for Larissa's labor? So ideally we'd aim for spontaneous labor, since the use of oxytocin increases the risk of uterine rupture, and the highest chance of success for a trial of labor after Caesarian section comes with spontaneous onset of labor. However, it's not always possible to await spontaneous labor, as there are some circumstances where an induction of labor might be recommended for the safety of the mother or the baby. It's important to have a discussion with Larissa early about what a preference has might be if an induction is indicated. There's an increased risk of uterine rupture with oxytocin used in induction, which is as we said before, quite at about 1 in 80 to 1 in 100. Induction is also associated with hyarates of failed V-back. If that risk is acceptable to Larissa, then it's a reasonable to proceed with an induction. However, if Larissa is uncomfortable with that risk profile, then she may choose to have an elective Caesarian instead of an induction. If we are going ahead with an induction of labor, it's important to consider previous Caesarian section in our method of induction. For cervical ripening, prostaglendants are known to increase the risk of uterine rupture compared to mechanical methods. For this reason, we would recommend mechanical cervical ripening with the balloon catheter or a follies. One study demonstrated rates of uterine rupture of 1.4 to 2.45% when labor had been induced with prostaglendants. That's not to say that prostaglendants are absolutely contraindicated, just that if they are used, they're being used against the manufacturers' instructions and should only be used in certain clinical situations after maintaining informed consent from the woman. We also know that oxytocin uses associated with an increased risk of uterine rupture, and so some women might choose to delay the onset of oxytocin after their ARM in the hopes that their contractions might start spontaneously. Typically, some facilities might offer a delay of 2 to 4 hours after ARM to allow contractions to establish prior to static centrosanone. Remember, the use of oxytocin almost doubles the risk of uterine rupture, an induction of labor is less likely to result in V back than spontaneous labor. Some women may be uncomfortable with the risk and therefore might choose a trial of labor in the event of spontaneous labor or a cesarean section if an induction is required. It's also important to differentiate the use of oxytocin for induction and the use of oxytocin for augmentation. FriendsCock recommends that augmentation for lack of progress in labor for a planned V back should involve a discussion with an obstetrician and the risks and benefits discussed with the patient. Augmenting a V back is associated with an increased risk of uterine rupture, especially in the case of obstructed labor, but a decreased risk of needing a cesarean section. If you're considering V back augmentation, then you really want a thorough assessment of why there's a lack of progress in labor. If every reason is inadequate contractions, then oxytocin might be useful, but it's important to exclude obstructed labor, fetal malpresentation, CPD, and rupture first. One Australian study demonstrated a 14 times difference in the odds ratio for uterine rupture in planned V back patients with spontaneous labor versus those augmented with oxytocin. The total rate was 1.9% of rupture, although the odds ratio in various studies ranged from 2.3 to 14. That's a good point about assessing why you're augmenting, because remember one of the signs of uterine rupture is an alteration to contraction, so if you've got someone who's laboring along normally and they're contracting well, and suddenly they're not contracting well, you really need to consider why before you just throw a centaur in the mix there. Absolutely, always think it in the back of your mind. And the moral of the story is that you can augment a V back, but you need to be cautious about it. If you need to be especially cautious with the rate of centaur. One study demonstrated a uterine rupture rate of 2.07% with centaur doses of 21 to 30 million units per minute. And I would definitely involve your consultant, always, always. Our next recommendation is to have a cannula in labor. This is because in the event of an emergency, like a uterine rupture, the patient would need urgent fluid resuscitation and transfer to theatre. If a woman chooses to not have a cannula in labor, then she should be informed that inserting a cannula in an emergency can lead to multiple mist attempts at cannulation and delay in administering treatment. Interestingly, the nice clinical guidelines and also the Queensland clinical guidelines suggest that routine siting of a cannula for V back is not required, unless difficult cannulation is anticipated or there are additional risk factors. However, the RANs caught guidelines and several other hospital guidelines still support the recommendation for cannula in labor. We also recommend a CTG in labor. The reason for this is that an abnormal CTG, maybe one of the earliest signs that a uterine rupture is occurring. It's interesting that the Queensland guidelines don't suggest having a cannula in. But if you work in a small unit, and there's not many people inside, and you have a uterine rupture, you don't really have the manpower to waste by putting someone's cannula in. I think that's why you really. Yeah. What a cool judgment. Yeah, and every Queensland hospital I've worked at has had a cannula in labor for V back. Yeah, I know, yes, I know. Interestingly, the nice guideline changes in a recommendation for management of labor with Vijana Birth after V back in 2019. The guideline initially said that an IVC in CTG monitoring are not required, but they've self-disoccurately changed their recommendation back again to recommend a CTG. I mean, it makes sense since that the early sign of uterine rupture is fetal distress. Having a CTG would allow uterine rupture to be detected in a timely manner, and a hanging in cannula would allow for rapid maternal resuscitation and delivery in the event that a uterine rupture occurred. Orel intake should be restricted to clear fluids because of the greater than normal probability of needing an immediate season to GA. Other recommendations from the RANSCA guideline include four hourly for general examinations in the active phase of labor, and more frequently as full dilatation approaches. Two hourly assessments from seven centimeters dilatation can help to detect a secondary arrest of labor. Now, these are important because you really wanted to detect obstructed labor early, because if you persist in labor with obstruction, you are much more likely to lead to a rupture. So then what about the management of early labor? What should we be telling these women when they ring up the maternity assessment unit or birth suite and let us know they're contracting regularly? I would recommend that patients attend hospital at the onset of contractions. As we mentioned before, the highest risk of rupture is at 4 to 5 centimeters, so we really want these women to come in so we can monitor them with a CTG. RANSCA recommends that women should be advised to have continuous electronic fetal monitoring following the onset of uterine contractions and for the duration of the planned feedback. If a uterine rupture does happen, then we want to diagnose it early and provide an urgent caesarian section in resuscitation for both mother and baby. Okay, so to summarize the key points of our V-Back consultation, review previous operative notes and the indication for delivery. Exclude contraindications to V-Back, identify current placental location and their risk of a creatile, determine future pregnancy plans and their motivations for either a V-Back or caesarian section. I like to ask women how many babies they're planning on having as well, to see how many caesars they would have in the future. Review obstetric and medical history. Use a V-Back calculator to provide individualized counseling on V-Back success rates. Discuss the risks and benefits of both a V-Back and elective caesare and provide written information on this. Discuss management plan if a patient wants a caesare but presents in labor. Discuss a management plan if the patient wants a V-Back but needs an induction and discuss intrapart of management. Recommend to present early in labor. There's a cannula in labor and continuous CTG monitoring. Yeah, you might remember from our previous episode that we said that 10% of book elective caesareans at 39 weeks will present in labor beforehand on Anne's night shifts. Yes, definitely. And it did happen. Okay, so let's do a bit of troubleshooting here. What about if we can't find the notes from the previous Caesar? It was done overseas or it's back on paper records from 20 years ago. So this can be tricky. I mean, if you can't see the opnets, then how do you know they didn't have a classical caesarian section or an inverted T or a J or some other contraindication? Well, you'd be forgiven for thinking that the safest option here is to recommend an elective repeat caesarean since you can't technically exclude any contraindications to V-Back. However,
They actually have been a few studies looking into the rates of uterine rupture and those with a known prior low transverse uterine incision versus those with an unknown type of uterine incision. And guess what? The rupture rate is actually the same. Acorgan up to date both suggests that if you don't know where the prior uterine incision was, then you can reasonably assume that it was a lower segment transverse incision since the vast majority of patients with a previous cesarean will have had that incision type. Obviously, if the patient had a preterm cesarean or has a known lower segment fibroid or was told that she is not suitable for V back, then we would have a higher suspicion that the prior uterine incision might have been made into the upper segment of the uterus in which case we would not recommend V back. What about single-verse double-layer uterine closure? Does that matter? As long we thought that a single-lay closure has a higher rate of uterine rupture. However this has not been shown to be true in studies. A retrospective Danish cohort study of 7,600 patients found no association between single-layer closure and uterine rupture when compared with double-layer closure. These findings are also consistent with the prior matter analysis. Therefore, a single-layer uterine closure is not a contraindication to V back. Ranscox states that there is conflicting evidence as to whether a single-layer can be made into a double-layer closure increases the risk of scar rupture. I also remember from our previous episode on the evidence-based cesarean section that a single-layer closure resulted in a reduced myometrial thickness compared to a double-layer closure. So why don't we just measure the myometrial thickness to assess the risk of uterine rupture? Unfortunately, ultrasound measurement of myometrial thickness has not been demonstrated to be sufficiently predictive or protective of uterine rupture to be useful in clinical practice. While it seems logical that a thinnest scar would have an increased risk of rupture, we don't actually have enough data to say what a safe myometrial thickness is. A thin myometrium actually has a low positive predictive value for rupture, and patients with normal lower uterine segment thickness have gone on to rupture their uterus when in labor. Despite the limitations in evidence, some clinicians consider a lower segment thickness of less than 2 mm to be predictive of an increased risk of rupture and incorporate this into clinical counseling overseas. Australia does not seem to use myometrial thickness in anti-natal counseling. And will an epidural mask of uterine rupture? Essentially no. There's no evidence that an epidural masks uterine rupture, or that it increases the risk of uterine rupture or failed feedback. In fact, an epidural might even be helpful in the event of a uterine rupture since it can facilitate a faster cesarean section. The Queensland clinical guidelines state that an epidural use during attempted feedback is associated with higher rates of feedback, higher rates of incidental birth, and similar rates of uterine rupture. Women should be allowed to utilize whichever pain manager at options they desire. Okay, and then what about if we have twins? So Ranskog states that a cautious approach is advocated in twin pregnancies who are considering feedback. However, this guideline was published in March 2019. A subsequent meta-analysis published in May 2019 showed no increased risk of uterine rupture, hemorrhage, morbidity, or neonatal mortality compared to singleton feedback. The pooled success rate was 72.2%, and the rate of uterine rupture was 0.87%. Therefore, twins should not be considered a contraindication to feedback. This year is also supported by the Queensland clinical guidelines. And what about a water birth or water immersion? A previous cesarean section is not a contraindication to water immersion, provided there's adequate fetal monitoring. Although keep in mind that every hospital has their own policy and water immersion and water birth, and so it's important to follow your local hospital guidelines, which is designed to keep both moms and babs safe. What about if you've heard more than one Caesar? So the main concern with attempting a V-back after two previous cesarean sections, or a V-back 2, is lower success rates, higher rates of uterine rupture, and increased maternal morbidity compared to a V-back 1. Queensland clinical guidelines suggest that V-back 2 is a reasonable option for women with a history of two or more priors as area sections, following counseling with an experienced obstetrician. This is based on a systematic review that reported a V-back rate of 71%, compared with 77% for V-back 1, a uterine rupture rate of 1.36%. And the fact that maternal morbidity for women undergoing a V-back 2 is actually similar to that of women undergoing their third cesarean section. There were no significant differences in neonatal morbidity, although the data was too limited to draw valid conclusions. Counseling and situation of a V-back 2 should definitely still be individualized. It's also really important to consider the service capabilities of the birthing facility when having discussions about V-back, especially in those cases where there is a higher chance of uterine rupture. Ideally, you need access to an emergency theater for cesarean, a blood-bedding area, and a bank and skilled staff in the event of a uterine rupture. A V-back in a tertiary centre is likely to be much safer than a V-back in a rural Australia where there's no access to emergency theater, for example. For these reasons, different hospitals may have different guidelines on what they consider to be acceptable and safe. Some hospitals might do their facilities inadequate to support a V-back 1, for example. These guidelines are there for a reason and it's important that you follow your local hospital guidelines. Okay folks, well that wraps up this week's episode on V-back. You'll find our study notes up on Instagram later in the week. If you have any feedback or opinions on anything we've discussed today, please contact us through our Instagram @TheUniranSound or on Facebook or email us at
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