Click here to view next page of this article
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