021815 parturition

Question 1

how do uterine contractions occur?

Answer 1

myometrial cells contract spontaneously (spontaneous action potential, so no hormonal or nervous input is needed)

Question 2

uterine contractions-biochemical basis?

Answer 2

action potential causes Ca influx into myometrial cell. activates Ca calmodulin complex. activates myosin light chain kinase. phosphorylates myosin, ATP is hydrolyzed, myosin undergoes structural change, and myosin interacts with actin

Question 3

labor phenotype

Answer 3

transition from quiescence phase to labor phase involves shift from progesterone dominance to estrogen dominance

uterine stretch and estrogen upregulate CONTRACTION ASSOCIATED PROTEINS in myometrium

Question 4

how does estrogen dominance at the end of pregnancy help the uterus?

Answer 4

increases gap jxns btwn myometrial cells

increases oxytocin receptor and PG receptor expression in myometrium

(progesterone during pregnancy inhibits expression of contraction associated proteins)

Question 5

contraction associated proteins-ex

Answer 5

gap jxn protein connexin
oxytocin receptor
corticotropin releasing hormone receptor
COX-2 enzyme

Question 6

oxytocin’s role

Answer 6

increases PG and estrogen level in labor phenotype

Question 7

stages of labor

Answer 7

first stage-latent phase and active phase. latent phase is contraction w slow cervical dilation. active phase is contractions with fast cervical dilation.

secondstage-complete dilation until delivery of fetus

third stage-post delivery to delivery of placenta

fourth stage-lasts one hr after delivery of placenta. constant myometrial contrac that limits blood loss

Question 8

preterm labor–mechanism?

Answer 8

the same as normal labor, but what leads to the labor is likely different

Question 9

risk factors for preterm labor

Answer 9

infections
smoking
genetics
cercial shortening/decreased uterine space
low pre-pregnancy weight, socioeconimic disadvantage

Question 10

tx for stopping preterm labor

Answer 10

magnesium
calcium channel blockers
beta 2 adrenergic receptor agonist
PG synthesis inhibitors (indomethacin-COX inhibitor)

these primarily act by preventing intracellular Ca influx

Question 11

what can be used to PREVENT preterm delivery?

Answer 11

progesterone

Question 12

tx for inducing labor

Answer 12

dinoprostone
misopristol
oxytocin

Question 13

atony

Answer 13

uterine relaxation during 4th stage of labor leading to excessive blood loss

Question 14

how do you tx post partum hemorrhage

Answer 14

uterine massage

oxytocin, PGs, ergot alkaloid ergonovine

Question 15

Sheehan syndrome

Answer 15

hypovolemia from obstetrical blood loss leads to pituitary infarction or necrosis

can hv amenorrhea for ex