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Flashcards in The Powers Deck (15):
1

Powers: Uterine Contractions cause (4)

1) Uterine Contractions cause effacement and dilation of cervix2) Descent of fetus3) Involuntary urge to push4) Voluntary bearing down in 2nd stage of labor helps with expulsion of fetus(ATI 121)

2

Powers: PRIMARY Contractions ( 4 phases)Primary and Secondary forces of labor

1) Build-up phase2) Acme (peak)3) Decrement (letting up phase)4) Resting phase (nadir)

3

Powers: PRIMARY Contractions: FREQUENCY (2)Primary and Secondary forces of labor

Frequency1) time or minutes2) onset of one contraction to the onset of the next contraction

4

Powers: PRIMARY Contractions: INTENSITYPrimary and Secondary forces of labor

Intensity1) Strength of contraction at the acme (peak), which can be palpated as mild, moderate, strong, or detected with a fetal monitor externally or measured internally in mmHG(Hogan 161)

5

Powers: PRIMARY Contractions: DURATIONPrimary and Secondary forces of labor

DurationLength of contraction measured in seconds from beginning of increment to end of decrement

6

Powers: SECONDARY Contractions: (3)

1) Voluntary use of abd muscles2) During second stage of labor3) To facilitate fetal descent and delivery

7

Powers: PRIMARY Contractions: Effacement (4)

1) With each contraction muscles of upper uterine segment shorten2) Drawing up of internal os and cervical canal into uterine sides3) Measure 0-100% 4) Multigravidas effacement and dilation normally occur simultaneously

8

Powers: PRIMARY Contractions: Dilatation

1) As uterus elongates with contractions2) Fetal body straightens and exerts pressure against lower uterine segment and cervix3) Measure 0-10 cm

9

Powers: Maternal Factor Theories (3)
1) Uterus
2) Oxytocin Stimulation Theory
3) Progesterone Withdrawal Theory

(Gray ppt)

Maternal Factor Theories
1) Uterus is stretched to threshold point
Synthesis and release of prostaglandin

2) Oxytocin stimulation theory
Oxytocin known to stimulate myometrial contractions
Progesterone inhibits myometrical response throughout pregnancy
Estrogen at term enhances myometrial sensitivity to oxytocin
A surge of oxytocin may be released by the stretching of the cervix at term (Ferguson’s reflex)

3) Progesterone withdrawal theory
Progesterone-estrogen ratio leads to increased myometrical contractility

10

Powers: Fetal Factor Theories
1) Placental aging
2) Fetal Cortisol Theory
3) Prostaglandin Synthesis Theory

(Gray ppt)

Fetal Factor Theories
1) Placental aging triggers initiation of contractions
2) Fetal Cortisol Theory
Normal fetal adrenal glands produce a steroid, cortisol, which stimulate the onset of labor
3) Prostaglandin synthesis Theory
Present in increased quantities in blood and amniotic fluid during labor

11

Power of Labor: Physiology of Contractions
1) Myometrium
2) Contractions

(Gray ppt)

1) Myometrium
Alpha-receptors stimulate uterine contractions
Beta-receptors stimulate uterine relaxation

2) Contraction
The shortening of a muscle in response to the stimulate
Increment – building up, longest phase of contraction
Acme – peak
Decrement – letting up

12

Power of Labor: Physiology of Contractions
1) Retraction
2) Tonus

(Gray ppt)

1) Retraction
Uterine contraction
Upper segment of uterus becomes shorter and thicker
Lower segment of uterus becomes longer, thinner and more distended
Shortening and thickening of the upper segment leads to fetal descent

2) Tonus
Degree of pressure exerted by the uterine musculature as measured by intrauterine pressure

-Normal baseline between contractions is 8 to 12 mm Hg
-Pressure at peak of a contraction ranges from 35 to 75 mm Hg

13

Power of Labor: Physiology of Contractions
1) Intensity
2 Pacemaker

(Gray ppt)

1) Intensity
The difference between peak pressure and baseline pressure
30 to 50 mm Hg intensity for effective labor

2) Pacemaker – located fundus of the uterus
Contraction begins in the fundus then proceeds downward to the rest of the uterus (descending gradient)
Intensity of the contraction diminishes from top to bottom, so that the upper segment contracts more strongly than the longer segment

14

Power of Labor: Physiology of Contractions
Contraction Strength
1) Myometrial activity is responsible?
2) Uterine contractions create?
3) Myometrial effectiveness is improved by?
4) Lateral positions?
5) Walking and activity increases?
6) Relaxation mitigates?

(Gray ppt)

1) Contraction Strength
Myometrial activity is responsible for effacement and dilation of the 1st stage of labor
2) Uterine contractions create increased intrauterine pressure, which exerts tension on the cervix and pressure on the descending fetus.
3) Myometrial effectiveness is improved by good uterine blood flow
4) Lateral positions, avoid the vena caval syndrome
5) Walking and activity increases circulating blood to the uterus
6) Relaxation mitigates fight-or-flight response, avoiding diminished blood flow to uterus

15

Power of Labor: Physiology of Contractions
Contraction Strength
1) Effacement
2) Dilation

(Gray ppt)

Effacement
With each contraction, muscles of upper segment shorten, exerting longitudinal traction on cervix causing thinning and drawing up of internal os and cervical canal into uterine side walls
Measured from 0 to 100 %

Dilation
As uterus elongates with contractions, fetal body straightens out and exerts pressure against lower uterine segment and cervix. Cervix opens as a result, allowing for birth of fetus
Measured from 0 to 10 cm

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