Breech presentation refers to the fetus in the longitudinal lie with the buttocks or lower extremity entering the pelvis first. The three types of breech presentation include frank breech, complete breech, and incomplete breech. In a frank breech, the fetus has flexion of both hips, and the legs are straight with the feet near the fetal face, in a pike position. The complete breech has the fetus sitting with flexion of both hips and both legs in a tuck position. Finally, the incomplete breech can have any combination of one or both hips extended, also known as footling (one leg extended) breech, or double footling breech (both legs extended).
Clinical conditions associated with breech presentation include those that may increase or decrease fetal motility, or affect the vertical polarity of the uterine cavity. Prematurity, multiple gestations, aneuploidies, congenital anomalies, Mullerian anomalies, uterine leiomyoma, and placental polarity as in placenta previa are most commonly associated with a breech presentation. Also, a previous history of breech presentation at term increases the risk of repeat breech presentation at term in subsequent pregnancies. These are discussed in more detail in the pathophysiology section.
Breech presentation occurs in 3% to 4% of all term pregnancies. A higher percentage of breech presentations occurs with less advanced gestational age. At 32 weeks, 7% of fetuses are breech, and 28 weeks or less, 25% are breech.
Specifically, following one breech delivery, the recurrence rate for the second pregnancy was nearly 10%, and for a subsequent third pregnancy, it was 27%. Prior cesarean delivery has also been described by some to increase the incidence of breech presentation two-fold.
As mentioned previously, the most common clinical conditions or disease processes that result in the breech presentation are those that affect fetal motility or the vertical polarity of the uterine cavity.
Conditions that change the vertical polarity or the uterine cavity, or affect the ease or ability of the fetus to turn into the vertex presentation in the third trimester include:
The risk of cord prolapse varies depending on the type of breech. Incomplete or footling breech carries the highest risk of cord prolapse at 15% to 18%, while complete breech is lower at 4% to 6%, and frank breech is uncommon at 0.5%.
During the physical exam, using the Leopold maneuvers, palpation of a hard, round, mobile structure at the fundus and the inability to palpate a presenting part in the lower abdomen superior to the pubic bone or the engaged breech in the same area, should raise suspicion of a breech presentation.
During a cervical exam, findings may include the lack of a palpable presenting part, palpation of a lower extremity, usually a foot, or for the engaged breech, palpation of the soft tissue of the fetal buttocks may be noted. If the patient has been laboring, caution is warranted as the soft tissue of the fetal buttocks may be interpreted as caput of the fetal vertex.
Any of these findings should raise suspicion and ultrasound should be performed.
Diagnosis of a breech presentation can be accomplished through abdominal exam using the Leopold maneuvers in combination with the cervical exam. Ultrasound should confirm the diagnosis.
On ultrasound, the fetal lie and presenting part should be visualized and documented. If breech presentation is diagnosed, specific information including the specific type of breech, the degree of flexion of the fetal head, estimated fetal weight, amniotic fluid volume, placental location, and fetal anatomy review (if not already done previously) should be documented.
Expertise in the delivery of the vaginal breech baby is becoming less common due to fewer vaginal breech deliveries being offered throughout the United States and in most industrialized countries. The Term Breech Trial (TBT), a well-designed, multicenter, international, randomized controlled trial published in 2000 compared planned vaginal delivery to planned cesarean delivery for the term breech infant. The investigators reported that delivery by planned cesarean resulted in significantly lower perinatal mortality, neonatal mortality, and serious neonatal morbidity. Also, there was no significant difference in maternal morbidity or mortality between the two groups. Since that time, the rate of term breech infants delivered by planned cesarean has increased dramatically. Follow-up studies to the TBT have been published looking at maternal morbidity and outcomes of the children at two years. Although these reports did not show any significant difference in the risk of death and neurodevelopmental, these studies were felt to be underpowered.
Since the TBT, many authors since have argued that there are still some specific situations that vaginal breech delivery is a potential, safe alternative to planned cesarean. Many smaller retrospective studies have reported no difference in neonatal morbidity or mortality using these specific criteria.
The initial criteria used in these reports were similar: gestational age greater than 37 weeks, frank or complete breech presentation, no fetal anomalies on ultrasound examination, adequate maternal pelvis, and estimated fetal weight between 2500 g and 4000 g. In addition, the protocol presented by one report required documentation of fetal head flexion and adequate amniotic fluid volume, defined as a 3-cm vertical pocket. Oxytocin induction or augmentation was not offered, and strict criteria were established for normal labor progress. CT pelvimetry did determine an adequate maternal pelvis.
Despite debate on both sides, the current recommendation for the breech presentation at term includes offering external cephalic version (ECV) to those patients that meet criteria, and for those whom are not candidates or decline external cephalic version, a planned cesarean section for delivery sometime after 39 weeks.
Regarding the premature breech, gestational age will determine the mode of delivery. Before 26 weeks, there is a lack of quality clinical evidence to guide mode of delivery. One large retrospective cohort study recently concluded that from 28 to 31 6/7 weeks, there is a significant decrease in perinatal morbidity and mortality in a planned cesarean delivery versus intended vaginal delivery, while there is no difference in perinatal morbidity and mortality in gestational age 32 to 36 weeks. Of note, due to lack of recruitment, no prospective clinical trials are examining this issue.
In light of the decrease in planned vaginal breech deliveries, thus the decrease in expertise in managing this clinical scenario, it is prudent that policies requiring simulation and instruction in the delivery technique for vaginal breech birth are established to care for the emergency breech vaginal delivery.