LC Exam 2: Parturition

Question 1

Pressure changes during labor and blood flow

Answer 1

Uterine smooth muscle at rest: 25mmHg
Contraction: up to 120mmHg
Pain is ischemic from spiral arteries (placenta is transiently hypoxic, but Wharton’s jelly maintained baby perfusion)

Question 2

Structure of the cervix and dilation

Answer 2

Mostly collagen 1 and 3
Dilates with contractions, proteases degrade
Internal portion is the part that needs to be dilated (melts away)
Dilation easier in multi-pardous women

Question 3

Cervical insufficiency

Answer 3

Painless delivery early - miscarrage

Disorganized cervical collagen, can’t hold baby

Question 4

Stages of labor

Answer 4

1: Contractions to obtain dilation of cervix
2: Complete dilation to delivery of fetus
3: Delivery of fetus to delivery of placenta
4: First 6 hours post

Question 5

Myometrial phases of labor

Answer 5

0: Quiescence
1: Activation
2: Stimulation (marks 1st stage of labor)
3: Involution (4th stage of labor)

Question 6

Hormonal keys of myometrial phases

Answer 6

0: Progesterone
1: Estrogen, progesterone (receptor switching), uterine stretch, fetal signal (CRH)
2: Prostaglandins, oxytocin, CRH
3: Oxytocin, inflammatory cells

Question 7

Uterus growth during pregnancy

Answer 7

Lots of growth
Increased oxytocin receptor density
Becomes synctyal electrical system (synchonicity):
Increased connexon density/gap jxns
Mechanotransmission as well

Question 8

Myometrial inhibtors

Answer 8

Progesterone (blocks myosin light chain, PG inhibitor)

CRH (quiescence in early pregnancy)

Question 9

Myometrial stimulators

Answer 9

CRH (later)
Oxytocin (receptor increase in labor)
Prostoglandins (receptor increase in labor)
Ca2+ (channel increase in labor)

Question 10

Oxytocin

Answer 10

Stimulates contraction
Increases Ca2+
Activates myosin LC kinase
Increases PG

Question 11

Prostaglandins

Answer 11

Source: myometrium, placenta
Increases Ca2+
Weakens amnion and chorion
Membrane PG DH decreases during labor, which increases PG levels

Question 12

CRH

Answer 12

Switches fxn
Early: quiesence, blocks myosin LC kinase (cAMP, NO)
Late: contraction, activates PKC
Receptor switching
CRH levels increase late (fetus production)
CRHBG goes down at end of preg

Question 13

Preterm labor treatments

Answer 13

Can only delay up to 48 hours, give course of steroids
Calcium antag
Oxytocin antag
PG inhibitors
NO donors
Beta-mimetics
Mg2+

Question 14

Ligand - receptor - action:
Prostaglandin
Oxytocin
Epi

Answer 14

PGE2/PGE1 - EP1: Gq - myometrial contraction
PGE2/PGE1 - EP2-4: Gs - cervical ripening/dilation
PGF2a - FP: Gq - myometrial contaction
Oxytocin - OXT: Gq - myometrial contaction
Epi - ß2: Gs - myometrial RELAXATION

Question 15

Stages and hormones

Answer 15

Stage 1: cervical dilation = prostaglandin
Stage 2: uterine contaction = PG/oxytocin via L-type Ca and ß2 for relaxation
Stage 3: placental delivery = oxytocin hemostasis

Question 16

Misoprostol

Dinoprostone

Answer 16

M: PGE1 - EP1R in myometrium (better systemically)
D: PGE2 - EP1R in myometrium (lots of AR systemically, can do locally for cervical effect as well)
Note: EP2-4 in cervix

Question 17

Pitocin

Answer 17

Oxytocin analoge
Milk letdown
Labor induction (no effect on cervix, needs to be dilated)
Useful for postpartum bleeding

Question 18

Tocolytic agent use and agents

Answer 18

Delay pregnancy up to 48 hours
Betamethasone for lung development
Can’t use cortisol -> placenta inactivates

Terbutaline, indomethacin, ethanol, Mg, Nifedipine

Question 19

Terbutaline

Answer 19

ß2-agonist
Suppresses contractions, not after 48-72 hours
No affect on PG - less effective is dilated and ruptured
Maternal side effects

Question 20

Indomethacin

Answer 20

COX 1 and 2 blocker, inhibits PG’s
Used 24-32 weeks
PG -> maintain patent DA

Question 21

Ethanol

Answer 21

Theoretical. Not used.

Question 22

MgSO4

Answer 22

Older medication, not used unless anticonvulsant for pre-ecamplsia/ecamplisia
Compete with Ca2+

Question 23

Nifedipine

Answer 23

Ca channel blocker
Used 32-34 weeks (can use 24-32 if CI to indo.)
Fewer side effects than Mg or ß-ag

Question 24

17 a hydroxyprogeterone caporate

Answer 24

Progesterone metabolite
Prevent preterm labor
Given 1 week/IM at 16/20 wks pregnant until 36 wks
Hx of >/=1 previous spontaneous preterm birth

Question 25

Mifepristone

Answer 25

Progesterone antagonist
Early termination
Followed 36-48 hours by prostaglandin to contract rest of contents
(Uterus insensitive to oxytocin until 20-36 weeks)