Breech presentation

For other uses, see Breech (disambiguation).
Breech birth
Classification and external resources
10 9 DiseasesDB MedlinePlus eMedicine MeSH D001946

A breech birth is the birth of a baby from a breech presentation, in which the baby exits the pelvis with the buttocks or feet first as opposed to the normal head-first presentation. In breech presentation, fetal heart sounds are heard just above the umblicus.

The bottom-down position presents some hazards to the baby during the process of birth, and the mode of delivery (vaginal versus Caesarean) is controversial in the fields of obstetrics and midwifery.

Though vaginal birth is possible for the breech baby, certain fetal and maternal factors influence the safety of vaginal breech birth. The majority of breech babies born in the United States are delivered by Caesarean section.

Etiology

Certain factors, such as premature birth, can encourage a breech presentation. Approximately 25 percent of fetuses are in the breech position 32 weeks into gestation; this drops to about 3 percent at term.[1] Towards term, the fetal buttocks and legs increase in size, causing a tendency for these parts to move towards the more distended top of the uterus, reducing the incidence of breech presentation. Pregnancies ending in preterm birth simply recruit more breeches before they can turn to head down. Factors predisposing to term breech presentation include:

It is postulated that the baby normally assumes a head down presentation because of the weight of the baby's head. As the mass of the fetal head is the same as that of the pelvis, it is more likely that the enlarging fetus is more and more restricted in its movements, and simply becomes entrapped. The shape of the uterus is a more likely determinant of the final fetal presentation as uterine shape anomalies are strong predictors of breech presentation and other malpresentations.

Epidemiology

Researchers generally cite a breech presentation frequency at term of 3–4%[3][4] at the onset of labour though some claim a frequency as high as 7%.[5] When labour is premature, the incidence of breech presentation is higher. At 28 weeks' gestation 25% of babies are breech, and the percentage decreases approaching term (36 weeks' gestation).

Categories

There are either three or four main categories of breech births, depending upon the source:

  • Frank breech – the baby's bottom comes first, and his or her legs are flexed at the hip and extended at the knees (with feet near the ears); 65–70% of breech babies are in the frank breech position
  • Complete breech – the baby's hips and knees are flexed so that the baby is sitting crosslegged, with feet beside the bottom
  • Footling breech – one or both feet come first, with the bottom at a higher position; this is rare at term but relatively common with premature fetuses
  • Kneeling breech – the baby is in a kneeling position, with one or both legs extended at the hips and flexed at the knees; this is extremely rare, and is excluded from many classifications

In addition to the above, breech births in which the sacrum is the fetal denominator can be classified by the position of a fetus. Thus sacro-anterior, sacro-transverse and sacro-posterior positions all exist, but left sacro-anterior is the commonest presentation. Sacro-anterior indicates an easier delivery compared to other forms.

Process of breech birth

As in labour with a baby in a normal head-down position, uterine contractions typically occur at regular intervals and gradually cause the cervix to become thinner and to open. In the more common breech presentations, the baby’s bottom (rather than feet or knees) is what is first to descend through the maternal pelvis and emerge from the vagina.

At the beginning of labour, the baby is generally in an oblique position, facing either the right or left side of the mother's back. The baby's bottom is the same size in the term baby as the baby's head. Descent is thus as for the presenting fetal head and delay in descent is a cardinal sign of possible problems with the delivery of the head.

In order to begin the birth, descent of podalic pole along with compaction and internal rotation needs to occur. This happens when the mother's pelvic floor muscles cause the baby to turn so that it can be born with one hip directly in front of the other. At this point the baby is facing one of the mother's inner thighs. Then, the shoulders follow the same path as the hips did. At this time the baby usually turns to face the mother's back. Next occurs external rotation, which is when the shoulders emerge as the baby’s head enters the maternal pelvis. The combination of maternal muscle tone and uterine contractions cause the baby’s head to flex, chin to chest. Then the back of the baby's head emerges and finally the face.

Due to the increased pressure during labour and birth, it is normal for the baby's leading hip to be bruised and genitalia to be swollen. Babies who assumed the frank breech position in utero may continue to hold their legs in this position for some days after birth.

Risks

Umbilical cord prolapse may occur, particularly in the complete, footling, or kneeling breech. This is caused by the lowermost parts of the baby not completely filling the space of the dilated cervix. When the waters break the amniotic sac, it is possible for the umbilical cord to drop down and become compressed. This complication severely diminishes oxygen flow to the baby and the baby must be delivered immediately (usually by Caesarean section) so that he or she can breathe. If there is a delay in delivery, the brain can be damaged. Among full-term, head-down babies, cord prolapse is quite rare, occurring in 0.4 percent. Among frank breech babies the incidence is 0.5 percent, among complete breeches 4 to 6 percent, and among footling breeches 15 to 18 percent.

Head entrapment is caused by the failure of the fetal head to negotiate the maternal midpelvis. At full term, the fetal bitrochanteric diameter (the distance between the outer points of the hips) is about the same as the biparietal diameter (the transverse diameter of the skull)—simply put the size of the hips are the same as the size of the head. The relatively larger buttocks dilate the cervix as effectively as the head does in the typical head-down presentation. In contrast, the relative head size of a preterm baby is greater than the fetal buttocks. If the baby is preterm, it may be possible for the baby’s body to emerge while the cervix has not dilated enough for the head to emerge.

Because the umbilical cord—the baby’s oxygen supply—is significantly compressed while the head is in the pelvis during a breech birth, it is important that the delivery of the aftercoming fetal head not be delayed. The head only just fits through the pelvis, and if the arm is extended alongside the head, delivery will not occur. If this occurs, the Løvset manoeuvre may be employed, or the arm may be manually brought to a position in front of the chest. The Løvset manoeuvre involves rotating the fetal body by holding the fetal pelvis. Twisting the body such that an arm trails behind the shoulder, it will tend to cross down over the face to a position where it can be reached by the obstetrician's finger, and brought to a position below the head. A similar rotation in the opposite direction is made to deliver the other arm. In order to present the smallest diameter (9.5 cm) to the pelvis, the baby’s head must be flexed (chin to chest). If the head is in a deflexed position, the risk of entrapment is increased. Uterine contractions and maternal muscle tone encourage the head to flex. If the birth attendant pulls on the baby’s body, this action may deflex the head.

Oxygen deprivation may occur from either cord prolapse or prolonged compression of the cord during birth, as in head entrapment. If oxygen deprivation is prolonged, it may cause permanent neurological damage (for instance, cerebral palsy) or death.

Injury to the brain and skull may occur due to the rapid passage of the baby's head through the mother's pelvis. This causes rapid decompression of the baby's head. In contrast, a baby going through labor in the head-down position usually experiences gradual molding (temporary reshaping of the skull) over the course of a few hours. This sudden compression and decompression in breech birth may cause no problems at all, but it can injure the brain. This injury is more likely in preterm babies. The fetal head may be controlled by a special two-handed grip call the Mariceau-Smellie-Veit manoeuvre or the elective application of forceps. This will be of value in controlling the rate of delivery of the head and reduce decompression. Related to potential head trauma, researchers have identified a relationship between breech birth and autism.[6]

Squeezing the baby’s abdomen can damage internal organs. Positioning the baby incorrectly while using forceps to deliver the aftercoming head can damage the spine or spinal cord. It is important for the birth attendant to be knowledgeable, skilled, and experienced with all variations of breech birth. In the United States, because Cesarean section is increasingly being used for breech babies, fewer and fewer birth attendants are developing these skills.

Factors influencing the safety

  • Type of breech presentation – the frank breech has the most favorable outcomes in vaginal birth, with many studies suggesting no difference in outcome compared to head down babies. (Some studies, however, find that planned caesarean sections for all breech babies improve outcome. The difference may rest in part on the skill of the doctors who delivered babies in different studies.) Complete breech presentation is the next most favorable position, but these babies sometimes shift and become footling breeches during labour. Footling and kneeling breeches have a higher risk of cord prolapse and head entrapment.
  • Parity – Parity refers to the number of times a woman has given birth before. If a woman has given birth vaginally, her pelvis has "proven" it is big enough to allow a baby of that baby's size to pass through it. However, a head-down baby's head often molds (shifts its shape to fit the maternal pelvis) and so may present a smaller diameter than the same-size baby born breech. Research on the issue has been contradictory as far as whether vaginal breech birth is safer when the mother has given birth before, or not.
  • Fetal size in relation to maternal pelvic size – If the mother's pelvis is roomy and the baby is not large, this is favorable for vaginal breech delivery. However, prenatal estimates of the size of the baby and the size of the pelvis are unreliable.
  • Hyperextension of the fetal head – this can be evaluated with ultrasound. Less than 5% of breech babies have their heads in the "star-gazing" position, face looking straight upwards and the back of the head resting against the back of the neck. Caesarean delivery is absolutely necessary, because vaginal birth with the baby's head in this position confers a high risk of spinal cord trauma and death.
  • Maturity of the baby – Premature babies appear to be at higher risk of complications if delivered vaginally than if delivered by caesarean section.
  • Progress of labor – A spontaneous, normally progressing, straightforward labor requiring no intervention is a favorable sign.
  • Second twins – If a first twin is born head down and the second twin is breech, the chances are good that the second twin can have a safe breech birth.
  • Birth attendant's skill (and experience with breech birth) – The skill of the doctor or midwife and the number of breech births previously assisted is of crucial importance. Many of the dangers in vaginal birth for breech babies come from mistakes made by birth attendants.

Turning the baby to avoid a breech birth

There are many methods which have been attempted with the aim of turning breech babies, with varying degrees of success:

  • External cephalic version where a midwife or doctor turns the baby by manipulating the baby through the mother's abdomen. ECV has a success rate between 40–70% depending on practitioner.[7] The fetal heart is monitored after the turn attempt, usually in the context of an institutional protocol. Studies show that turning the baby at term (after 36 weeks) is effective in reducing the number of babies born in the breech position.[8] Complications from external cephalic version are rare. Studies have also shown that attempting to turn the baby prior to this point has no impact on the presentation at term.[9]

Using hypothetical scenarios, a small study in the Netherlands found that few obstetric practitioners would attempt ECV in the presence of oligohydramnios.[10] A case report of treating oligohydramnios with amnioinfusion, followed by ECV, was successful in turning the fetus.[11]

Various maneuvers are suggested to assist spontaneous version of a breech presenting pregnancy. These include maternal positioning or other exercises. A study has shown that there is insufficient evidence as to the benefit of maternal positioning in reducing the incidence of breech presentation.[9]

Breech birth versus Caesarean section

Caesarean section is the most common way to deliver a breech baby in Australia, the United Kingdom, and the United States. Like any major surgery, it involves risks. Maternal mortality is increased by a Caesarean section, but still remains a rare complication in developed countries. Third World statistics are dramatically different, and mortality is increased significantly. There is remote risk of injury to the mother's internal organs, injury to the baby, and severe hemorrhage requiring hysterectomy with resultant infertility.

One large study has confirmed that elective Cesarean section has lower risk to the fetus and a slightly increased risk to the mother than planned vaginal delivery of the breech.[12] However, elements of the methodology used have undergone some criticism.[13][14]

See also

References

External links

  • Breech birth controversies in Great Britain
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.