Labor and delivery

Question 1

What vitamin (?) plays a role in controlling uterine muscle contraction

Answer 1

Calcium!
Ca flows into cytoplasm w/ transporters through channels
Ca-ATPase and Na/Ca exchangers maintain IC calcium homeostasis

Question 2

Uterine contractions depend on

Answer 2

formation of contractile protein actomysin and hydrolysis of ATP to produce motion

Question 3

What has an inhibitory effect on uterine contraction

Answer 3

ATP sensitive potassium channel stimulation AKA open K channels
(hyperpolarization of myometrial cells)

Question 4

Why do we have uterine contractions in labor

Answer 4

Promote cervical ripening (soft, thin cervix)
Control post-partum hemorrhage (MCC of perinatal maternal death)
Terminate pregnancy

Question 5

What drugs promote uterine contractions

Answer 5

Oxytocin: induce labor (contractions), promote cervical ripening
PGE2: promote cervical ripening and contractions
Carboprost: control postpartum hemorrhage
Mifepristone: terminate pregnancy
Methylergonovine: control postpartum hemorrhage

Question 6

How does oxytocin work

Answer 6

opens non-specific cation channels= open L type Ca channels= release of Ca from sarcoplasmic reticulum and decrease Ca efflux

Question 7

How do you dose oxytocin

Answer 7

Start low and gradually increase to desired effect

Question 8

Excessive uterine contractions can lead to

Answer 8

Uterine rupture

Fetal distress

Question 9

How do you use the PGE2 (dinoprostone) gel and how does it work (prepidil)

Answer 9

Place in cervical canal= cervical ripening
promotes uterine contractions
*Place in cervix when you plan on inducing labor w/ oxytocin in 1-2 days

Question 10

How do you place PGE2 (dinoprostone) vaginal insert (cervidil)

Answer 10

insert into posterior fornix of vagina

remove just before delivery

Question 11

Vaginal suppository of PGE2 can be used to

Answer 11

Terminate pregnancy 2/2 missed abortion, IU fetal death, and benign hydatiform mole); it is basically a stronger version (20mg) of Cervidil (10mg) and Prostadil (1/2 mg)
Can be used from week 12-20 of gestation

Question 12

ADE for all PGE2 include

Answer 12

nausea
vomiting
+/- fever
HTN and hypotension have been reported

Question 13

How does Carboprost work

Answer 13

Methylated analogue of PGF2a given IM; causes strong uterine contractions that is good for postpartum hemorrhage
Can induce uterine emptying at 13-20 weeks gestation, but NOT for elective abortions with a viable infant

Question 14

ADE of carboprost include

Answer 14

Bronchospasm (DO NOT use in asthma!) 
Hypertension 
Diarrhea 
Vomiting 
"Choking"

Question 15

How does Mifepristone work

Answer 15

Progesterone antagonist used to terminate pregnancy through 49 day of gestation
-Also used off label for cushing’s

Question 16

Why can Oxytocin be given postpartum

Answer 16

To enhance uterine contraction
given as a single IV infusion over several minutes
Must give after delivery of placenta

Question 17

How does Methylergonovine work

Answer 17

Causes uterine contractions and vasoconstriction

given IM postpartum (IV use discouraged 2/2 severe HTN and CVA)

Question 18

What are “tocolytic” agents

Answer 18

Agents that suppress uterine contractions, used MC to suppress labor that would result in a premie infant AKA women24-34 weeks at risk for delivering in the next 7 days
Prolong labor 48 hrs-1 week

Question 19

Tocolytic agents allow for use of other drugs to

Answer 19

accelerate fetal lung maturity!
Betamethasone IM q24 hrs, 2 doses
Dexamethasone IM q12 hrs, 4 doses

Question 20

What drugs suppress uterine contractions

Answer 20

Terbutaline (beta-2 agonist)
Nifedipine (inhibit calcium entry)
NSAIDs
MgSO4 (magnesium sulfate)

Question 21

What is an antidote to excess calcium

Answer 21

Magnesium sulfate!

Question 22

How does Terbutaline prolong labor (off label)

Answer 22

Causes uterine smooth muscle relaxation (like beta2 agonists do!) in airways and peripheral vasculature
Oral, subQ, or IV

Question 23

ADE of Terbutaline include

Answer 23

Tachycardia 
Pulmonary edema 
hypokalemia 
metabolic acidosis 
hypotension

Question 24

Black box warning for Terbutaline is

Answer 24

Do not oral dose or prolong parenteral use beyond 48-72 hours; risk of maternal cardiotoxicity an death!

Question 25

How long can MgSO4 be used to prolong pregnancy

Answer 25

5-7 days MAX!
Longer use can lead to hypocalcemia and increased risk of osteopenia and bone fractures in newborns
FDA not changed MgSO4 to a category D drug 2/2 evidence of human fetal risk

Question 26

IV mag sulfate CAN be used for

Answer 26

neuroprotection!

When used during preterm labor, incidence of moderate to severe cerebral palsy was reduced 50%

Question 27

ADE of Magnesium sulfate include

Answer 27

High serum magnesium= weakness, paralysis, respiratory failure, hypotension

Question 28

Because Mg is renally eliminated…

Answer 28

Renalinsufficiency impairs Mg elimination and can lead to toxicity

Question 29

In severe Mg toxicity, use

Answer 29

Hemodialysis to lower Mg levels

-In moderate cases IV calcium shots can be used

Question 30

How does nifedipine work

Answer 30

CCB; relaxes uterine smooth muscle and vascular muscle

Question 31

ADE of nifedipine include

Answer 31

Constipation

Question 32

How do NSAIDs help in prolonging labor

Answer 32

inhibit PG release= no uterine contractions! also inhibit platelet aggregation
They are 2/3 line and should only be used as tocolytics

Question 33

ADE of NSAIDs include

Answer 33

decreased GFR in baby

Narrowing or closure of fetal ductus arteriosus

Question 34

Hydroxyprogesterone caproate is given IM weekly to

Answer 34

maintain pregnancy in women with a Hx of recurrent miscarriage at >20 weeks
Begin weekly injection at 16 weeks
(these women are not progesterone deficient, but you can give progesterone to enhance uterine relaxation)