Chapter 12: Process Of Birth Flashcards
What are the three phases of the contraction cycle?
- Increment
- Peak
- Decrement
Contraction Cycle: Increment
Occurs as the contraction begins in the fundus and spreads throughout the uterus.
Starts to incline and works its way up with strength.
Contraction Cycle: Peak
Or acme, is the period during which the contraction is most intense.
Patient feels the most intense pain.
Contraction Cycle: Decrement
The period of decreasing intensity as the uterine relaxes; decline of the contraction.
Patterns of contraction include what factors
- Frequency
- Duration
- Intensity
- Interval-resting tone
Frequency of contractions
The period from the beginning of one uterine contraction to the beginning of the next.
Frequency of contractions is expressed in
Minutes and fractions of minutes (i.e “contractions are 3 1/2 to 4 minutes apart”)
Resting tone needs to last how long for the baby to be reperfused?
Needs to last at least 60 seconds.
Duration of contractions
The length of each contraction from beginning to end.
How is duration of contractions expressed?
In seconds (i.e “her contractions last 55-65 seconds”)
What is the average duration of contractions?
About 2-4 minutes, lasting 60-90 seconds.
What is the purpose of contractions?
Is so that the cervix can dilate and she can deliver her baby.
Can’t deliver without contractions.
Intensity of contractions are described as
Mild, moderate or strong as palpated by the nurse.
Interval resting tone
- Period between the end of one contraction and the beginning of the next.
- Most fetal exchange of oxygen, nutrients and waste products occurs in the placenta at this time.
Uterine Body during labor: Upper 2/3
- The upper 2/3 of the uterus contracts actively to push the fetus down.
- Myometrial cells remain shorter at the end of each contraction.
Uterine Body during labor: Lower 1/3
- Remains less active, promoting downward passage of the fetus.
- Myometrial cells become longer with each contraction.
- Cervix is also passive.
Cervical changes during labor include
Effacement and dilation (occurs concurrently during labor but at different rates)
Cervical effacement in a nullipara
Completes most cervical effacement early in the process of cervical dilation
Cervical effacement in Paribus women
Cervix is usually thicker than that of a nullipara at any point during labor.
Nullipara
Woman who has never completed a pregnancy beyond a spontaneous or elective abortion.
Parous
Having given birth to one or more viable children.
Effacement
Thinning and shortening of the cervix.
Process of Effacement:
- Before labor the cervix is a cylindric structure about 2 cm long at the lower end of the uterus
- Labor contractions push the fetus downward against the cervix while pulling the cervix upward
- If the membranes are intact, hydrostatic (fluid) pressure of the amniotic sac adds to the force of the presenting part on the cervix
- As it is drawn over the fetus and amniotic sac the muscles of upper uterine segment shorten and cause cervix to thin and flatten
- The cervix merges with the thinning lower uterus rather than remaining a distinct cylindric structure
Effacement is estimated as
A percentage of the original cervical length.
A fully thinned cervix is
100% effaced
Effacement may also be documented as
The cervical length estimated during vaginal examination.
Dilation occurs as
The cervix is pulled upward and the fetus is pushed downward.
Full dilation is approximately
10 cm
What happens to HR during contraction?
- It increases.
- Also increase in CO d/t increased blood volume when blood flow is shunted back into mom’s circulation.
When is the best time to take vital signs in a woman during labor?
Between contractions because if you take VS during contraction, there is reduced blood flow to the uterus which temporarily increases maternal blood volume, CO and increases BP.
During each uterine contraction, blood flow to the placenta
Gradually decreases, causing a relative increase in the woman’s blood volume.
Respiratory system changes during labor
- Increase in oxygen demand and consumption
- Depth and rate of respiration increases, especially if the woman is anxious or in pain.
Respiratory system changes during the first stage of labor
Mom is going to hyperventilate as she starts to get a little bit uncomfortable d/t consistent, painful contractions -> leads to mild respiratory alkalosis**
What is important to do to help relieve mild respiratory alkalosis during the first stage of labor?
Calm the patient down and slow breathing.
Respiratory changes during the second stage of labor
At this stage, mom is pushing.
Mother tends to hold breath while pushing which can lead to mild respiratory acidosis**
Fetal response to mom pushing and holding her breath for a prolonged period of time can result in
Temporary mild fetal metabolic acidosis (typically reversible when baby takes first respiratory gasp of air after brith)
In a baby with temporary mild fetal metabolic acidosis, the nurse needs to
- Stimulate/give a little O2 to baby to get him going
- Obtain cord pH and evaluate metabolic changes.
Blood loss during labor
- 500 mL as the maximum normal blood loss during vaginal birth
- Loss usually tolerated well because the blood volume increases during pregnancy by 1 to 2 L (30-40%)
Blood loss in women with anemia
Women with anemia at the beginning of labor has less reserve for normal blood loss.
Have poor tolerance for excess bleeding.
What is the adequate margin of safety for blood loss associated with normal birth?
Hgb: 10.5 g/dL
Hct: 33%
WBC changes during labor
Leukocyte count averages 14,000-16,000/mm3 but may be as high as 25,000/mm3 or more during active labor or with no other evidence of infection.
Changes in clotting factors during labor
- Clotting factors, especially fibrinogen, are elevated during pregnancy and continue to be higher during labor and after delivery.
- This provides protection from hemorrhage but also increases the mother’s risk for venous thrombosis during pregnancy and after birth.
Changes in the GI system during labor include
- Decreased motility (can result in N/V)
- Increased thirst and dry mouth (ice chips, small amounts of clear liquids, juices, popsicles and hard non-sugar candy can be given)
- Prolonged emptying
- Risk for aspiration
Changes in the urinary system during labor include
- Reduced sensation of a full bladder d/t contractions and effects of regional anesthesia
- Edema can occur at base of bladder d/t pressure from fetal head.
How can a full bladder effect labor?
- Fetal descent may be inhabited by full bladder because it occupies space in the pelvis.
- Can contribute to discomfort.
Hypervolemia during pregnancy is reversed
-During the first 5 days postpartum as large quantities of urine is excreted.
Fetal responses during labor
- May have no adverse effects
- May not tolerate labor contractions well in conditions associated with reduced placental function. (I.e HTN, diabetes, fetal anemia)
- Acidosis d/t decreased blood flow during peak of contraction and when mother holds breath during pushing.
- FHR may decrease as head pushes against cervix -> early deceleration
What are protective fetal mechanisms include
- Fetal hemoglobin (hemoglobin F which more readily takes on oxygen and releases carbon dioxide
- High hemoglobin and hematocrit levels that can carry 20% to 50% more oxygen than adult hemoglobin
- A high cardiac output of 250 mL/kg/min
The fetal hemoglobin level averages
14.5 to 22.5 g/dL
Average fetal hematocrit is
approximately 48% to 69%
Catecholamines
- Primarily epinephrine and norepinephrine.
- Produced by fetal adrenal glands in response to the stress of labor contributes to the infant’s adaptation to extrauterine life.
How do catecholamines help infants during labor?
- Stimulates cardiac contraction and breathing
- Quickens the clearance of remaining lung fluid
- Aids in temperature regulation.
What are the four P’s that interact during normal childbirth?
- Power
- Passage
- Passenger
- Psyche
Powers include
1st stage of labor: Uterine contractions
2nd stage of labor: Maternal pushing efforts
Powers: Uterine Contractions
Onset to full cervical dilation.
Contractions are the primary force that moves the fetus through the maternal pelvis.
Powers: Maternal Pushing Efforts
- Full cervical dilation to birth of the baby.
- Uterine contractions continue to propel the fetus through the pelvis as woman feels urge to push and bear down as the fetus distends her vagina and puts pressure on her rectum.
- She adds voluntary pushing efforts to the force of uterine contractions in second stage labor.
Passage
Consists of the maternal pelvis and soft tissues.
Why is the bony pelvis usually more important to the outcome of labor than the soft tissue?
Because of increased levels of the hormone relaxin.
Lines Terminalis
Pelvic brim that divides the pelvis into the false pelvis (top) and true pelvis (bottom).
The true pelvis has 3 divisions:
- Inlet/upper portion of the pelvic opening
- Mid pelvis
- Outlet/lower pelvic opening
Mid pelvis
Area where we have ischial spine.
Want baby to descend into midpelvis and stay down there.
Cephalopelvic Disproportion
Baby’s head is too big to get into pelvis.
Outlet/lower pelvic opening
Once baby has reached the outlet, it is ready to come out.
Passenger
Is the fetus, membranes and placenta.
Fetus enters the birth canal in what presentation?
Cephalic presentation
Anterior fontanel is connected by what four sutures?
2 coronal, 1 frontal and 1 saggital
The posterior fontanel is connected by what 3 sutures?
2 lambdoid and 1 sagittal
Variation in the passenger includes
- Fetal lie
- Attitude
- Presentation
Fetal lie
Orientation of the long axis of the fetus to the long axis of the woman.
Types of fetal lie
- Longitudinal (vertical)
- Transverse: long axis of fetus is at a right angle to the woman’s long axis.
- Oblique: some angle between longitudinal and transverse lie.
Attitude
The relation of fetal body parts to one another.
Normal fetal attitude is
- One of flexion with head flexed toward the chest and the arms and legs flexed over the thorax.
- Back is curved in a convex “C” shape.
Fetal presentation
The fetal part that first enters the pelvis .
Presentation falls into three categories:
- Cephalic
- Breech
- Shoulder
Cephalic Presentation
Most common and more favorable.
After the head is born, the smaller parts follow early as the extremities unfold.
Cephalic Presentation has four variations:
- Vertex/occiput
- Military: neither flexed nor extended
- Brow: head is partly extended
- Face: head is extended
Breech Presentation
Fetal buttocks enter the pelvis first
Breech position is more common in
- preterm births
- hydrocephalus (prevents the head from entering the pelvis)
- placenta previa (placenta in the lower uterus)
In breech position, because the umbilical cord can be compressed after the fetal chest is born,
The head must be delivered quickly to allow the infants to breathe.
Breech Presentation has 3 variations
- Frank breech: legs are extended across the abdomen toward the shoulders
- Full (complete) breech: head, knees, hips are flexed but buttocks are presenting.
- Footling breech: occurs eh one or both feet are presenting
Shoulder Presentation
Shoulder presentation is a transverse.
Occurs more often with preterm birth, high parity, PROM, hydramnios and placenta previa.
Compound presentation
Where the head and the hands are together.
Difficult to deliver and can’t deliver as a result.
Fetal Position
- 4 Quadrants: Right anterior, left anterior, left posterior, right posterior.
- First letter represents right or left; if neither, than first letter is omitted.
- Second later refers to the fixed fetal reference point.
Fixed fetal reference points
O: occiput=vertex presentation M: mentum=chin S: sacrum=breech presentation F: fronto=brow Sc: scapula=shoulder representation
Psyche
Response to labor and birth influenced by anxiety, culture, expectation, life experience and support.
Psyche can include
- Anxiety
- Culture
- Expectations/life experiences
- Support
How can anxiety affect labor?
- Maternal catecholamines secreted in response to anxiety and fear can inhibit uterine contractility and placental blood flow
- Relaxation augments the natural process of labor
How can expectations/life experiences affect a woman’s labor?
● Woman’s past experience w/ childbirth, pain, personal success and failure will influence her expectations for this birth.
● Woman’s sense of control and mastery during birth help her perceive the birth as a positive event.
Support during labor
includes physical comfort measures, providing information, advocacy, praise and reassurance, presence, and the maintenance of a calm and comfortable environment.
The cephalic presentation is more favorable than others for several reasons:
- The fetal head is the largest single fetal part, although the breech (buttocks), with the legs and feet flexed on the abdomen, is collectively larger than the head. After the head is born, the smaller parts follow easily as the extremities unfold.
- During labor, the fetal head can gradually change shape, molding to adapt to the size and shape of the maternal pelvis.
- The fetal head is smooth, round, and hard, making it a more effective part to dilate the cervix, which is also round.
