breech presentation

breech presentation

Breech Presentation: A Comprehensive Guide

1. Introduction

As the complexity of obstetrics has increased, the management of breech presentations has been a source of controversy. Breech presentation is the most common abnormal presentation in the third trimester of pregnancy. In the 1950s, the cesarean section rate for breech presentation was 30%. In 2006, the Term Breech Trial was stopped early due to increased perinatal mortality and morbidity in the planned vaginal delivery group. This has resulted in a tendency for professionals to recommend cesarean section more often for breech presentation. However, cesarean section is not without risks to the mother and baby, and does not mean that complications will be avoided. An understanding of the potential complications of both vaginal delivery and cesarean section for breech presentation is essential to provide informed consent to a patient. This article will discuss the presentation of a normal singleton fetus, the risks, benefits, and potential complications of both cesarean section and vaginal delivery, and provide an evidence-based approach to the management of a term singleton breech. This will only address breech presentation diagnosed at term, as the management of preterm breech presentation varies.

2. Understanding Breech Presentation

What causes a baby to be in a breech presentation? The incidence of breech presentation was higher in the past, as high as 25% in the 1950’s. Since then, the incidence has decreased to 3-4%. This is largely because women often delivered with breech presentation rather than have a cesarean section. A breech presentation is described by the part of the fetus that is presenting in the pelvis. There are three types of breech presentation. The frank breech is the most common. The hips are flexed and the knees are extended so the baby is sitting with its legs in a pike position and the feet by the ears. In a complete breech, the hips and knees are both flexed so that the baby is sitting cross-legged. Lastly, in a footling breech, one or both of the baby’s feet will be presenting. This is the most unstable lie of the breech presentation and the most dangerous for the baby during delivery. There are many factors that will affect the position of the fetus in a pregnancy. Each woman will have a unique set of circumstances that lead to why she may have a baby in a breech presentation. The uterus is a big muscle and it is divided into different segments. The top segment is the fundus. This muscle has to stretch to allow the baby to move up towards term. If there is an abnormality such as a fibroid, shape distortions from a previous surgery, a congenital anomaly, or a mal-presentation such as a twin, this will mean that there is a restriction of space in the uterus. Any of these can be a reason why a baby is in a breech presentation.

3. Risks and Complications

Early and late preterm birth Preterm birth (before 37 weeks) can occur as either an early or late preterm birth. Early preterm birth refers to babies born before 32 weeks of gestation, moderate preterm is between 32-33 weeks, and late preterm is 34-36 weeks gestation. Infants who are born at under 37 weeks gestation in a breech position have a higher neonatal morbidity and mortality rate compared to those born in a vertex presentation, especially those who are born early or moderately preterm. Babies who are early or moderately preterm with a breech presentation have a greater risk of experiencing perinatal mortality, birth trauma, cerebral palsy, and low Apgar scores. The overall neonatal death or injury rate is much higher for term babies in vertex presentation. Late preterm neonates may not have the same risk of mortality and morbidity as their moderate and early preterm counterparts but still have a higher incidence rate of being admitted to special care baby units. The reason for the increased risk of adverse outcomes in preterm babies with a breech presentation is that currently, the optimal mode of delivery for preterm breech babies is unclear. The Term Breech Trial concluded that delivery by planned caesarean section, where possible, is the optimal mode of delivery for breech presentation, due to means of reducing the risk of neonatal death and short-term serious neonatal morbidity for the baby. However, a difficulty is that the trial only looked at babies of a gestational age of 36 weeks or more. With a lack of evidence of what the optimal mode of delivery should be for a preterm breech baby, and the risk of perinatal mortality increasing before 36 weeks, there is difficulty in making a decision on how to best deliver these babies. Opting for an earlier delivery does not necessarily reduce the risk of neonatal death or morbidity and carries the risk of iatrogenic prematurity, with an early preterm birth having the highest risk of CP and other neurological impairments. Although the rate of caesarean section increases with decreasing gestational age at term, and across all modes of delivery, there is a trend of less favorable outcomes for the baby compared to those born at term.

4. Management and Treatment Options

Management of breech presentation should be individualized and counselling of the mother should be carried out to facilitate an informed decision. The option of external cephalic version should be discussed at around 36-37 weeks. This is a safe and effective procedure for selected patients, which reduces the chance of non-cephalic presentation at delivery and the risk of caesarean section, especially in nulliparous women. A Cochrane review found that women who had a planned caesarean section for a term singleton breech presentation had a reduced risk of perinatal or neonatal death and the risk of the baby having a low Apgar score [less than 7] at one minute. The outcome for the term baby was better with a planned caesarean section as there was also a reduced risk of the baby having birth trauma and a fractured skull. There are also reports of babies born by caesarean section having a reduced risk of transient tachypnoea. The safety of vaginal breech delivery relies heavily on clinical skills that are becoming increasingly rare. A Canadian study found that perinatal mortality and morbidity was increased for women who had a trial of vaginal breech delivery when the attending physician was inexperienced in this skill. With the Term Breech Trial only suggesting that delivery by elective caesarean section reduces the risk of the baby dying or suffering serious injury around the time of birth, it is still not possible to ignore the potential benefit for some women of an experienced practitioner performing a trial of vaginal breech delivery. A detailed explanation and discussion of the risks and benefits should be carried out and may suffice to appropriately allow informed consent. A recently published study comparing planned caesarean section with planned vaginal birth for breech presentation at term has added weight to the argument that the delivery by caesarean should be chosen for this clinical scenario due to the relative safety and to reduction of neonatal morbidity. This should avoid a blanket policy being adopted for all women which may be seen by some as a defensive medicine.

5. Conclusion

During the 35 years since the Term Breech Trial was published in 2000, the favorable outcome for planned cesarean section (CS) established this as the preferred mode of delivery for a breech fetus. The skill required to safely assist a singleton breech delivery with forceps or vacuum was still being taught at that time, so it is not surprising that the subsequent dramatic decrease in the skill and experience in vaginal breech delivery has been accompanied by an increase in the already significant risk. Planned CS may be the safest and most efficient mode for the average practitioner, but it is safe vaginal delivery that is safer than delivery by any other operative mode. Recognizing this, there is now a significant movement of women who seek skilled providers to facilitate a trial of labor. For these women, offering a safe alternative to planned cesarean section requires developing mechanisms to identify optimal candidates and a training system for those willing to provide the service. Ideal candidates are women in whom the risk of vaginal delivery is less than the combined risks of prelabor CS and failed attempt at VBAC. A newly published multivariate regression analysis offered an equation by which the probability of successful vaginal delivery may be estimated with reasonable accuracy. Continuing work in this direction will have to include development of predictive models with improved accuracy and ultimately a prospective randomized trial of planned vaginal delivery vs. planned CS. The common theme throughout these articles is the skill and experience of the provider. This plays a critical role in the safety of a breech delivery, such that an incompetent provider may put the mother and baby at unnecessary risk regardless of the mode of delivery. Indicative of the skill required is a Canadian study of over 6000 women that was terminated early due to concern about increased perinatal mortality in the group randomized to planned vaginal delivery. In a subsequent analysis, the authors revealed that none of the 144 deaths in the vaginal arm were directly related to the mode of delivery. Rather, the deaths were possibly preventable by CS due to suboptimal practitioner skills and a lack of the knowledge regarding which fetuses were at highest risk for adverse outcome. Such findings invoke an ethical concern about the proposed mode of delivery in ongoing randomized trials. Ideally, patients will be presented with an accurate, unbiased, complete picture of the risks and benefits of each mode of delivery. Current data does not fulfill this criterion, but as indicated by the new movement toward optimizing candidate selection, continued research holds promise for a clearer understanding with more specific recommendations. Continuation of this research will also allow a more accurate assessment of patient preferences. An informed consent process must offer more than the common assurance that the delivery method decision is at the discretion of the patient’s personal obstetrician. Women deserve information about the preferences and biases of their provider, and the ability to select a setting in which their preferences are most likely to be honored.