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Flashcards in Parturition Deck (45)
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1

4 clinical stages of labor

1. Effective contractions to complete dilation of the cervix
2. Complete dilation (10cm) to delivery of the fetus
3. Delivery of the fetus to delivery of the placenta (30 min)
4. First 6 hours after delivery

2

myometrial activation (phase 1)

1

3

Mechanism of myometrial quiescence (phase 0)

1

4

Progesterone in quiescence and parturition

Myometrial inhibitors:

Quiescence mid- trimester

Reduced activity MAY contribute to labor last trimester
- progesterone withdrawal activates mitogen-associated protein kinase and increases contractility

5

CRH in quiescence and parturition

Myometrial inhibitors:
- maintains quiescence mid trimester

Myometrial stimulants:
- Signal for parturition, last trimester
- Change in receptors

6

Cortisol in quiescence and parturition

1

7

Oxytocin in quiescence and parturition

Myometrial stimulants

- Stimulates contractions
- Differential distribution on uterus, highest at fundus

8

Contraction activated proteins (CAPS) and their contribution to contractility

CAPS protein synthesis
1. Gap jxns
2. Calcium channels
3. Oxytocin receptors
4. Prostaglandin receptors

- act within the uterus, to initiate powerful rhythmic contractions

Three types of CAPs:
1. Those that enhance the intxns betwn actin + myosin --> muscle contraction
2. Those that increase excitability of myometrial cells
3. Those that promote the intercellular connectivity that permits the development of synchronous contractions

9

How do myometrial calcium increases near term

1

10

Role of fetal HPA axis in partuition

1

11

Labor

effective uterine contractions leading to dilation and effacement of the cervix and delivery of the fetus

12

In between contraction

During contraction

blood flow in and blood flow out is good

Blood flow in and out is stopped

13

Carries deoxygenated blood

umbilical arteries

14

5 fxns of cervix

1. Baby in
2. Baby out
3. Endometrium out
4. Sperm in
5. Bugs out (keep infxns from ascending)

15

Structure of cervix

1. Stroma is collagen I & II
2. Collagen has linked strands
3. Proteases degrade collagen
4. Edema in later pregnancy
5. Dilates passively with contractions

16

Power
Myometrial expulsive efforts
+
Maternal expulsive efforts

Phase 0 - Quiescence
Phase 1 - Activation
Phase 2 - Stimulation
Phase 3 - Involution

Maternal expulsive efforts
- Push push push!

17

Myometrial phase 2

Stimulation
involves:
1. Contraction to dilation
2. Dilation to baby
3. Baby to Placenta

18

Myometrial phase 3

6 hours post partum

19

Uterus changes during pregnancy

1. 50g --> 1000g

2. Growth primarily cellular hypertrophy
3. Increased connectivity
4. Increased oxytocin receptors 100-200x
5. Receptors most highly [ ] in fundus

20

Synchronicity theory
- Action potential propagation in regions

1. EMG's of the abdomen in labor
2. Estimated 20-30 of these
3. Myofibril Cells connected by gap jxns
4. Think Goldberg polyhedron *soccer

Mechano-transduction across the uterus
- one region contract --> P rises
- Triggers stretch initiated contractions elsewhere
- Synchrony is achieved by electrical conduction through connecting myofibrils --> transmits electrical activity to nearby muscle fibers --> activated myocytes produce prostaglandins --> act in paracrine fashion to depolarize neighboring myocytes

21

Prostaglandins

fxn: stimulates contraction

Mechanisms:
1. Act in a paracrine fashion
2. Increase intracellular calcium levels
3. Facilitates weakening of amnion and chorion

22

CRH
*see slide

fxn:
Early pregnancy - Quiescence
Late pregnancy - Contraction (stim labor)

Mechanisms:
1. Early pregnancy - blocks myosin light chain kinase
2. Late pregnancy - Protein kinase C pathway

Positive feedback system on maternal side

Pulmonary maturation on fetal side

23

Term labor weeks

37-42 weeks

24

How does CRH help with fetal pulmonary maturity?

CRH stimulates labor

CRH induce fetal pulmonary maturity

*less morbidity with labor than with C section
- absence of above

25

Oxytocin
Fxn
Mech

Fxn: stimulates contraction

Mechanisms:
1. Binds membrane receptors
2. Increases intracellular calcium levels
3. Activates myosin light chain kinase
4. Activate prostaglanding E & F2 alpha production
5. Increases intracellular calcium lvls
6. activates myosin light chain kinase

26

Progesterone at term

- Blocks myosin light chain kinase
- Inactivates prostaglandins

1. Progesterone lvls high
2. reduced receptor number
3. different receptor types
4. less progesterone activity

27

Preterm birth occurs in how many pregnancies?

5-15%
*rising in developed countries
- esp in black Americans
- birth b4 37 weeks of gestation assoc. w/ 70% of neonatal deaths

*black women have lower maternal CRH [ ] than others that correlate with timing of birth

28

The timing of birth is associated with the development of what?

maternal CRH - which is made by the placenta (syncytiotrophoblast)

29

Diff between release of maternal plasma CRH lvls at term and preterm, and after term.

term: CRH lvls increase exponentially

preterm: CRH exponential increase is super rapid

After term: rise is slower

30

What stimulates expression of the CRH gene and production of CRH by the placenta?

Glucocorticoids

GC --> CRH --> stim pituitary to produce corticotropin --> stim adrenal cortex to produce cortisol + DHEAS