- Breech presentation occurs when the fetal pelvis or lower extremities engage the maternal pelvic inlet.
- Breech presentation may be suspected based on clinical examination, either by palpating fetal parts over the maternal abdomen or by pelvic examination.
- The diagnosis can be confirmed via ultrasound.
Breech presentation, which complicates 3–4% of all pregnancies, occurs when the fetal pelvis or lower extremities engage the maternal pelvic inlet. Three types of breech are distinguished, according to fetal attitude (Fig. 19–1). In frank breech, the hips are flexed with extended knees bilaterally. In complete breech, both hips and knees are flexed. In footling breech, 1 (single footling breech) or both (double footling breech) legs are extended below the level of the buttocks.
Types of breech presentations. (Reproduced, with permission, from Pernoll ML. Benson and Pernoll's Handbook of Obstetrics and Gynecology. 10th ed. New York, NY: McGraw-Hill; 2001.)
In singleton breech presentations in which the infant weighs less than 2500 g, 40% are frank breech, 10% complete breech, and 50% footling breech. With birth weights of more than 2500 g, 65% are frank breech, 10% complete breech, and 25% footling breech. The incidences of singleton breech presentations by birth weight and gestational age are listed in Table 19–1.
Table 19–1. Incidence of Singleton Breech Presentations by Birthweight and Gestational Age. ||Download (.pdf)
Table 19–1. Incidence of Singleton Breech Presentations by Birthweight and Gestational Age.
|Birthweight (g)||Gestational Age (weeks)||Incidence (%)|
Fetal position in breech presentation is determined by using the fetal sacrum as the point of reference to the maternal pelvis. This is true for frank, complete, and footling breeches. Eight possible positions are recognized: sacrum anterior (SA), sacrum posterior (SP), left sacrum transverse (LST), right sacrum transverse (RST), left sacrum anterior (LSA), left sacrum posterior (LSP), right sacrum anterior (RSA), and right sacrum posterior (RSP). The station of the breech presenting part is the location of the fetal sacrum with regard to the maternal ischial spines.
Before 28 weeks, the fetus is small enough in relation to intrauterine volume to rotate from cephalic to breech presentation and back again with relative ease. As gestational age and fetal weight increase, the relative decrease in intrauterine volume makes such changes more difficult. In most cases, the fetus spontaneously assumes the cephalic presentation to better accommodate the bulkier breech pole in the roomier fundal portion of the uterus.
Breech presentation occurs when spontaneous version to cephalic presentation is prevented as term approaches or if labor and delivery occur prematurely before cephalic version has ...