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LABOR AND DELIVERY:

INTRAPARTUM COMPLICATIONS, TWINS, AND BREECH

NORMAL LABOR

Oxytocin

Posterior pituitary peptide hormone with increasing sensitivity atterm (100 times greater)

Released by nipple stimulation and possibly by Ferguson reflex

Ethanol suppression will decrease Braxton-Hicks contractions but not active

Fetal oxytocin production may be necessary to maintain (1) Spontaneous (cord blood) greater than (maternal) (2) C-section prior to (cord blood) equal to (maternal) (3) Induced (cord blood) less than (maternal)

Estrogen-progesterone ratio induction of estrogen stimulates uterine growth

Alters cell membrane permeability to Na+, K+, and CI-, thus changing the resting excitability of the cell.

Induces gap junction formation

Decreases b-adrenergic receptors

Increases a-adrenergic and oxytocin receptors

Progesterone

Blocks formation of estrogen receptors (3) Increases b-adrenergic receptors

Role for the estrogen-progesterone ratio (1) Placereal sulfatase deficiency (2) Animal models

Estrogen will initiate

Progesterone withdrawal will initiate

Progesterone will not stop

Historically, premature patients were thought to have low progesterone

An approximate progesterone:estrogen::8:1 ratio has been hypothesized as necessary to maintain pregnancy

Adrenocorticosteroid

a. In sheep, an intact hypophyseal-pituitary-adrenal axis is necessary twins, breech, Pitocin oxytocin, dystocia fetal monitoring for the normal initiation

If surgically interrupted in the fetus, the pregnancy is prolonged

Adrenoconicotropic hormone (ACTH) and cortisol can induce