Classification and variants
In obstetrics practice, several main types of fetal positioning are distinguished:
- Frank breech (incomplete): only the buttocks present to the pelvic inlet, the legs are flexed at the hips and extended at the knees (stretched along the torso). This is the most frequent variant, accounting for 64%.
- Complete breech (mixed): buttocks along with feet present to the inlet, the legs are flexed at both joints ("squatting" pose).
- Footling presentations: form already during labor after rupture of membranes. They can be complete (both feet present) or incomplete (one foot presents, while the other is extended at the knee joint).
- Knee presentations: legs are flexed at the knee joints, occurring extremely rarely (0.3%).
Causes of formation
The general mechanism of development is associated with the creation of obstacles to the engagement of the head into the pelvic inlet. All etiological factors are divided into three groups:
- Maternal: uterine developmental anomalies (bicornuate, septate/subseptate), myoma (especially nodes in the lower segment), pelvic tumors and bone deformations, anatomically narrow pelvis, as well as decreased uterine tone in multiparous women.
- Fetal: multiple pregnancy, prematurity, fetal growth restriction, congenital anomalies (anencephaly, hydrocephaly), amniotic fluid pathology (oligohydramnios or polyhydramnios), abnormal fetal lie/attitude, and immaturity of the vestibular apparatus.
- Placental: placenta previa (placenta praevia), which prevents the correct engagement of the head.
Diagnostics
Diagnosis is established comprehensively using external examination, auscultation, vaginal examination, and ultrasound:
- External examination (Leopold's maneuvers): a dense balloting head is palpated in the uterine fundus, and the fundus itself is located higher than normal. A large, slightly soft presenting part without the ability to ballot is palpated above the pelvic inlet.
- Auscultation: fetal heartbeat is best heard above the umbilicus or at its level.
- Ultrasound examination: allows precise determination of the presentation variant, fetal mass, amount of fluid, and the degree of head extension by the angle between the spine and the occiput (from a flexed state to excessive extension of less than 90°).
Briefly: answers to topical questions
What degrees of fetal head extension on ultrasound are distinguished in breech presentation?
According to ultrasound data, three degrees of fetal head extension are distinguished, which are evaluated by the angle between the spine and the occiput.
- Grade I — mild extension (angle from 100° to 110°, "military attitude").
- Grade II — moderate extension (angle from 90° to 100°).
- Grade III — excessive extension (angle less than 90°, "star-gazing").
At an angle greater than 110°, the head is considered flexed.
What classical manual aids are used for delivering the shoulder girdle and arms in breech presentation?
To deliver the shoulder girdle and arms, a classical manual aid is used, based on the rule of the homonymous hand. The right arm is delivered by the obstetrician's right hand, and the left arm by the left hand.
- Release of the posterior arm — the arm facing the perineum is always delivered first, extracting it by the elbow crease with a "washing motion".
- Release of the anterior arm — to transfer it toward the perineum, the fetal torso is rotated by 180°, after which it is extracted with a similar motion.
The aid is indicated for delayed birth of the shoulder girdle, nuchal arm, or head extension.
What maneuvers are used to deliver the aftercoming fetal head?
To deliver the aftercoming fetal head, classical manual aids are used to ensure its flexion and traction along the pelvic axis.
- Mauriceau–Levret–Lachapelle method — the fetal torso is placed on the obstetrician's forearm, fingers are inserted into the mouth or placed on the upper jaw to flex the head, while the other hand fixes the shoulders and occiput.
- Mauriceau-Smellie-Veit maneuver (Mauriceau-Smellie-Veit) — a similar method in which the index and middle fingers of the lower hand are placed on the upper jaw on both sides of the nose, and the middle finger of the upper hand presses on the occipital tuberosity.
What is the essence of Tsovyanov I manual maneuver in frank breech presentation?
Tsovyanov I manual maneuver consists of maintaining the normal fetal attitude to prevent nuchal arms and head extension.
- Grip — after crowning of the buttocks, the thumbs are placed on the fetal thighs, and the other four fingers on the sacrum.
- Advancement — the obstetrician's hands are kept at the vulvar ring. As the torso is born, the thumbs press the extended legs against the abdomen, and the other fingers move upward along the back.
This allows the legs to press the crossed arms against the chest, turning the fetal body into a cone expanding upward.
What are the indications for elective Cesarean section in breech presentation?
Indications for elective Cesarean section in breech presentation include a combination of the presentation with a number of complicating factors.
- Fetal weight — less than 2000 g or more than 3600–3800 g.
- Head position — Grade III head extension according to ultrasound data.
- Presentation variant — mixed breech presentation in primiparas.
- Multiple pregnancy — breech presentation of the first twin in primiparas.
- Maternal factors — primipara age over 30 years, contracted pelvis, uterine scar, genital malformations.
- Fetal factors — Grade III fetal growth restriction, signs of hypoxia, post-term pregnancy.
Frank breech — buttocks "cleanly" alone at the pelvic inlet (legs extended). Mixed — buttocks "mixed" with the feet (squatting).
Class and exam questions
Why is breech presentation dangerous for the fetus?
The less voluminous part (pelvic end) is born first, followed by the larger head. This creates serious mechanical difficulties during its birth, and the brain structures of such fetuses often have a lower degree of maturity.
At what gestational ages is breech presentation commonly observed?
At 24–26 weeks, it is observed in approximately 33% of cases due to the physiological immaturity of the fetal vestibular apparatus. The presentation is finally formed by 35–37 weeks of gestation.
How is the fetal heartbeat auscultated in breech presentation?
The fetal heartbeat is most clearly auscultated above the umbilicus (or at its level), to the right or left depending on the fetal position.
What else to study on this topic
- Anatomical and functional features of the fetal central nervous system in breech presentation
- Dynamics of fetal rotation in the third trimester of gestation
- Ultrasound assessment of the degree of flexion and extension of the fetal head
- Features of the biomechanism of labor at the beginning of the first stage
- Influence of the state of amniotic fluid and placenta on fetal position
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