OB FINAL STUDY GUIDE

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OB FINAL STUDY GUIDE
1. PREMONITORY SIGNS OF LABOR
a. Backache
b. Weight loss (1-3 lbs.)
c. Lightening
i. Fetal head descends into pelvis
ii. Around 14 days before labor
iii. Feeling that fetus has “dropped”
d. Easier breathing
e. Increased bladder pressure
i. Urinary frequency
ii. More pronounced w/ primigravida
f. Contractions
i. Starts w/ Braxton Hicks (irregular)
ii. Progresses in strength & regularity
g. Bloody show
i. Brownish, blood tinged mucus plug
1. Onset of cervical dilation & effacement
h. Energy burst
i. Gastrointestinal changes
j. Rupture of membranes
i. Can initiate labor or occur anytime during labor

2. FIVE FACTORS (“5 P’s”)
a. Affect & define labor & birth process
i. Passenger
1. Fetus & placenta
1. Fetal presentation
i. Part of the fetus that is entering pelvic inlet first
1. Occiput – back of the head
2. Mentum – chin
3. Scapula – shoulder
4. Breech – sacrum or feet
2. Lie
i. Relationship of maternal longitudinal axis (spine) to
fetal longitudinal axis (spine)
1. Transverse: Fetal long axis is horizontal
2. Forms right angle to maternal axis
3. Cannot have vaginal birth
4. Shoulder is presenting part
5. Cesarean required if fetus doesn’t rotate
3. Attitude

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i. Relationship of fetal body parts to one another
1. Fetal flexion
a. Chin flexed to chest
b. Extremities flexed into torso
2. Fetal extension
a. Chin extended away from chest
b. Extremities extended
4. Fetopelvic/Fetal position
i. Relationship of presenting part of fetus in reference
to its position as it relates to one of the 4 maternal
pelvic quadrants
1. Right (R) or left (L)
a. References either side of maternal
pelvis
2. Occiput (O), sacrum (S), mentum (M) or
scapula (Sc)
a. 2nd letter references presenting part
of fetus
3. Anterior (A), posterior (P) or transverse (T)
a. 3rd letter references part of maternal
pelvis
5. Station
i. Measurement of fetal descent in centimeters
1. Station 0 being level of imaginary line at
level of ischial spines
2. Minus stations superior to ischial spines
3. Plus stations inferior to ischial spines
ii. Passageway
1. Birth canal
1. Bony pelvis
i. Must be adequate to allow fetus to pass thru
2. Cervix
i. Must dilate & efface in response to contractions &
fetal decent
3. Pelvic floor
4. Vagina
5. Introitus (vaginal opening)
iii. Powers
1. Uterine contractions cause effacement during 1 st stage of labor
2. Dilation of cervix occurs once labor has begun & fetus is
descending
3. Involuntary urge to push
4. Voluntary bearing down in 2nd stage of labor

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5. Helps in expulsion of fetus
iv. Position
1. Client should engage in frequent position changes during labor
1. Increase comfort
2. Relieve fatigue
3. Promotes circulation
2. Position during 2nd stage is determined by:
1. Maternal reference
2. Provider preference
3. Condition of mother & fetus
v. Psychological response
1. Maternal stress
2. Tension
3. Anxiety
1. Can produce physiological changes that impair labor
progress

3. MECHANISM OF LABOR
a. Engagement
i. Presenting part passes pelvic inlet at level of ischial spines
ii. Usually biparietal (largest) diameter of fetal head
iii. Referred to as station 0
b. Descent
i. Progress of presenting part through pelvis
ii. Preferably occiput
iii. Measured by station during vaginal exam as either:
1. Negative (-) station: measured in centimeters if superior to station
0 & not yet engaged
2. Positive (+) station: measured in centimeters if inferior to station 0
c. Flexion
i. When fetal head meets resistance of cervix, pelvic wall or pelvic floor
ii. Head flexes, bringing chin close to chest
iii. Presenting smaller diameter to pass thru pelvis
d. Internal rotation
i. Fetal occiput ideally rotates to lateral anterior position as it progresses
from ischial spines to lower pelvis
ii. Corkscrew motion to pass thru pelvis
e. Extension
i. Fetal occiput passes under symphysis pubis
ii. Head is deflected anteriorly
iii. Born by extension of chin away from fetal chest
f. External Rotation “Restitution”


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i. After head is born, it rotates to position it occupied as it entered pelvic
inlet in alignment w/ fetal body
ii. Completes a ¼ turn to face transverse as anterior shoulder passes under
symphysis
g. Birth by Expulsion
i. After birth of head & shoulders, trunk of neonate is born by flexing
towards symphysis pubis

4. STAGES OF LABOR
a. First stage (12.5 hrs): onset of labor to complete dilation
i. Latent phase (4-6 hrs)
1. Onset of labor
2. Contractions
1. Irregular
2. Mild to moderate
3. Frequency: 5-30 min
4. Duration: 30-45 sec
3. Dilation: 0-3 cm
ii. Active phase (2-3 hrs)
1. Contractions
1. More regular
2. Moderate to strong
3. Frequency: 3-5 min
4. Duration: 40-70 sec
2. Dilation: 4-7 cm
iii. Transition (20-40 min)
1. Contractions
1. Strong to very strong
2. Frequency: 2-3 min
3. Duration: 45-90 sec
2. Dilation: 8-10 cm
1. Complete dilation (10 cm)
iv. Pain
1. Internal visceral pain
2. Back and leg pain
1. Caused by:
i. Dilation
ii. Effacement
iii. Stretching of the cervix
iv. Distention of the lower segment of the uterus
v. Contractions of the uterus with resultant uterine
ischemia
b. Second stage (5 min – 2 hrs)

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