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GENERAL CONSIDERATIONS

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Definition

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Breech presentation is a longitudinal lie with a variation in polarity. The fetal pelvis is the leading pole. The denominator is the sacrum. A right sacrum anterior (RSA) is a breech presentation where the fetal sacrum is in the right anterior quadrant of the mother's pelvis and the bitrochanteric diameter of the fetus is in the right oblique diameter of the pelvis (Fig. 25-1).

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FIGURE 25-1.

Positions of breech presentation. LSA, left sacrum anterior; LSP, left sacrum posterior; LST, left sacrum transverse; RSA, right sacrum anterior; RSP, right sacrum posterior; RST, right sacrum transverse.

Graphic Jump Location
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Incidence

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Breech presentation at delivery occurs in 3 to 4 percent of pregnancies. However, before 28 weeks of gestation, the incidence is about 25 percent. As term gestation approaches, the incidence decreases. In most cases, the fetus converts to the cephalic presentation by 34 weeks of gestation.

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Etiology

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As term approaches, the uterine cavity, in most cases, accommodates the fetus best in a longitudinal lie with a cephalic presentation. In many cases of breech presentation, no reason for the malpresentation can be found and, by exclusion, the cause is ascribed to chance. Some women deliver all their children as breeches, suggesting that the pelvis is so shaped that the breech fits better than the head.

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Breech presentation is more common at the end of the second trimester than near term; hence, fetal prematurity is associated frequently with this presentation.

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Maternal Factors
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Factors that influence the occurrence of breech presentation include (1) the uterine relaxation associated with high parity; (2) polyhydramnios, in which the excessive amount of amniotic fluid makes it easier for the fetus to change position; (3) oligohydramnios, in which, because of the small amount of fluid, the fetus is trapped in the position assumed in the second trimester; (4) uterine anomalies; (5) neoplasms, such as leiomyomata of the myometrium; (6) while contracted pelvis is an uncommon cause of breech presentation, anything that interferes with the entry of the fetal head into the pelvis may play a part in the etiology of breech presentation.

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Placental Factors
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Placental site: There is some evidence that implantation of the placenta in either cornual-fundal region tends to promote breech presentation. There is a positive association of breech with placenta previa.

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Fetal Factors
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Fetal factors that influence the occurrence of breech presentation include multiple pregnancy, hydrocephaly, anencephaly, chromosomal anomalies, and intrauterine fetal death.

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Notes and Comments

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  1. The patient commonly feels fetal movements in the lower abdomen and may complain of painful kicking against the rectum, vagina, and bladder

  2. Engagement before the onset of ...

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