Parturition

Question 1

_____ cells _____ in early pregnancy and _____ in later half of pregnancy

Answer 1

myometrial; proliferate; hypertrophy

Question 2

what are the biochemical steps of uterine contraction?

Answer 2

myometrial action potential –> increase in intracellular calcium –> calcium binds calmodulin –> myosin light chain kinase activated –> myosin is phosphorylated –> ATP is hydrolyzed –> myosin undergoes structural change –> myosin forms a crossbridge with actin leading to contraction

Question 3

labor phenotype: transition from the quiescent phase to labor phase involves a shift from _____ dominance to _____ dominance

Answer 3

progesterone; estrogen

Question 4

how does progesterone maintain quiescence before labor?

Answer 4

inhibits intracellular calcium entry, inhibits calcium release from sarcoplasmic reticulum, membrane hyperpolarization via K+ channels, inhibits expression of contraction-associated protein genes

Question 5

what is estrogen’s role during the labor phase?

Answer 5

increases gap junctions between myometrial cells allowing for contraction synchrony between cells, increases oxytocin receptor and prostaglandin receptor expression in myometrium (contraction-associated proteins)

Question 6

_____ and _____ upregulate contraction-associated proteins (CAP) in the myometrium

Answer 6

uterine stretch; estrogen

Question 7

what are the biochemical steps of labor?

Answer 7

oxytocin or prostaglandins bind to their respective G protein coupled receptors –> activates phospholipase C –> stimulates release of calcium from intracellular stores –> myosin light chain kinase activation –> myosin is phosphorylated –> ATP is hydrolyzed –> myosin undergoes structural change –> myosin forms a crossbridge with actin leading to contraction

Question 8

labor: oxytocin synthesized by _____ and stored in _____ increases _____ and ____ level

Answer 8

hypothalamus; posterior pituitary; prostaglandin; estrogen

Question 9

how does the fetal adrenal gland contribute to the trigger of labor cascade?

Answer 9

placental oxytocin, prostaglandins, placental CRH

Question 10

preterm labor: delivery before ___ weeks gestation

Answer 10

37

Question 11

how does infection lead to preterm labor?

Answer 11

toxins produced by bacteria stimulate cytokine production leading to prostaglandin release

Question 12

modifiable and non-modifiable risk factors for preterm labor

Answer 12

modifiable: infections and periodontal disease, smoking
non-modifiable: genetics, cervical shortening, decreased uterine space, low pre-pregnancy weight, socioeconomic disadvantage, ethnicity

Question 13

name 4 therapies used to STOP preterm contractions (tocolytics) and their mechanism of action

Answer 13

magnesium sulfate, beta-2 adrenergic receptor agonists, calcium channel blockers (nifedipine), prostaglandin synthesis inhibitors; all prevent intracellular calcium influx
indomethacin (COX inhibitor) is also used

Question 14

what therapy is used to PREVENT preterm delivery in patients with history of preterm delivery and for patients with a shortened cervix length by ultrasound?

Answer 14

progesterone

Question 15

postpartum hemorrhage: > _____ mL blood loss after vaginal delivery or > _____ mL blood loss after cesarean

Answer 15

500; 1000

Question 16

postparum hemorrhage: pathogenesis, treatment

Answer 16

uterine relaxation/atony during 4th stage of labor; uterine massage, oxytocin, prostaglandins, ergot alkaloid (ergonovine)

Question 17

medications used for labor induction

Answer 17

prostaglandins: dinoprostone (PGE2), misoprostol (synthetic derivative of PGE1), oxytocin (drug of choice)