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66 Cards in this Set

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Factors affecting labor--remembered as the five "P's"
passenger (fetus and placenta)
passageway (birth canal)
powers (contractions)
position of the mother and psychological response
Passenger--the movement of the passenger, or fetus, through the birth canal is determined by several interacting factors:
the size of the fetal head
fetal presentation
fetal lie
fetal attitude
fetal position
Size of the fetal head
Because of its size and relative rigidity, the fetal head has a major effect on the birth process. During labor, after rupture of membranes, palpation of fontanels and sutures during vaginal examination reveals fetal presentation, position, and attitude.
Two most important fontanels: anterior and posterior
anterior fontanel, larger of the two is diamond shaped, about 3 cm by 2 cm and lies at the junction of the sagittal, coronal, and frontal sutures. It closes by 18 months after birth.
Posterior fontanel: lies at the junction of the sutures of the two parietal bones and the once occipital bone, is triangular, and is about 1 cm by 2 cm. It closes 6 to 8 weeks after birth.
Sutures and fontanels make the skull flexible to accomodate the infant brain, which continues to grow for some time after birth.
Fetal presentation
Presentation refers to the part of the fetus that enters the pelvic inlet first and leads through the birth canal during labor at term.
Three main presentations
cephalic (head first) 96% of births
breech (buttocks or feet first) 3% of births
shoulder presentation 1% of births
Presenting part
cepahlic presentation -- usually the occiput; in a breech presentation -- it is the sacrum; in a shoulder presentation -- it is the scapula
Factors that determine the presenting part
fetal lie
fetal attitude
extension or flexion of the fetal head
Fetal lie
Lie is the relation of the long axis (spine) of the fetus to the long axis (spine) of the mother.
Two primary lies
longitudinal, or vertical in which the long axis of the fetus is parallel with the long axis of the mother.
Transverse, horizontal or oblique, in which the long axis of the fetus is at a right angle diagonal to the long axis of the mother.
Fetal Attitude
Attitude is the relation of the fetal body parts to each other.
Attitude: general flexion
normally the back of the fetus is rounded so that the chin is flexed on the chest, the thighs are flexed on the abdomen, and the legs are flexed at the knees. The arms are crossed over the thorax, and the umbilical cord lies between the arms and the legs.
Fetal Position
Position is the relation of the presenting part (occiput, sacrum, mentum (chin), or sinciput [deflexed vertex]) to the four quadrants of the mother's pelvis
Critical factors in Labor
Power -- contraction
Passage -- pelvis shape and configuration
Passenger -- fetus, movements and position
Psyche -- emotional system involved
Power
Primary muscle is uterus, abdominal muscles secondary
Physiology of contraction
Increment, acme, decrement
Relationship to effacement and dilation of cervix
Powers
Involuntary and voluntary powers combine to expel the fetus and placenta from the uterus. Involuntary uterine contractions, called the primary powers, signal the beginning of labor. Once the cervix has dilated, voluntary bearing-down efforts by the woman, called the secondary powers, augment the force of the involuntary contractions.
Terms used to describe these involuntary contractions
Frequency--the time from the beginning of one contraction to the beginning of the next
Duration--(length of contraction)
Intensity--(strength of contraction)
Primary Powers
are responsible for the effacement and dilation of the cervix and descent of the fetus.
Effacement of the cervix
means the shortening and thinning of the cervix during the first stage of labor.
Only a thin edge of the cervix can be palpated when effacement is complete.
Dilation of the cervix
occurs by the drawing upward of the musculofibrous components of the cervix, caused by strong uterine contractions.
Stretch receptors in the posterior vagina cause release of endogenous oxytocin that triggers the maternal urge to bear down, or the Ferguson reflex.
Secondary powers
As soon as the presenting part reaches the pelvic floor, the contractions change in character and become expulsive. The laboring woman experiences an involuntary urge to push. She uses secondary powers (bearing-down efforts) to aid in expulsion of the fetus as she contracts her diaphragm and abdominal muscles and pushes.
Secondary powers
have no effect on cervical dilation, but they are of considerable importance in the expulsion of the infant from the uterus and vagina after the cervix is fully dilated. Studies have shown that pushing in the second stage is more effective and the woman is less fatigued when she begins to push only after she has the urge to do so rather than beginning to push when she is fully dilated without an urge to do so.
Four basic types of pelvis
Gynecoid (the classic female type)
Android (resembling the male pelvis)
Anthropoid (resembling the pelvis of anthropoid apes
Platypelloid (the flat pelvis)
Gynecoid Pelvis
The gynecoid pelvis is the most common (50% of all women)
Best opportunity for vaginal birth
Android Pelvis
Sacrum is prominent less chance for vaginal birth (23% of all women)
Usual mode of birth -- cesarean
Anthropoid
24% of all women -- Fair chance of vaginal birth
Platypelloid
3% of all women -- poor chance of vaginal birth
Passenger -- Station
Station is the relation of the presenting part of the fetus to an imaginary line drawn between the maternal ischial spines and is a measure of the degree of descent of the presenting part of the fetus through the birth canal. The placement of the presenting part is measured in cm above or below the ischial spines.
Birth is imminent when the presenting part is at +4 to +5 cm. The station of the presenting part should be determined when labor begins so that the rate of descent of the fetus during labor can be accurately determined.
Passenger -- Engagement
Engagement is the term used to indicate that the largest transverse diameter of the presenting part (usually the biparietal diameter) has passed through the maternal pelvic brim or inlet into the true pelvis and usually corresponds to station 0. Engagement often occurs in the weeks just before labor begins in nulliparas and may occur before or during labor in multiparas. Engagement can be determined by abdominal or vaginal examination.
Leopolds's Maneuvers (Abdominal Palpation)
Leopold's maneuvers are performed with the woman lying on her back. These maneuvers help identify the following: (1) number of fetuses; (2) presenting part, fetal lie, and fetal attitude; (3) defree of the presenting part's descent into the pelvis; and (4) expected location of the PMI of the fetal heart rate (FHRs) on the woman's abdomen.
Leopold's Maneuvers
Wash hands
Ask woman to empty bladder
Position woman supine with one pillow under her head and with her knees slightly flexed.
Place small rolled towels under woman's right or left hip to displace uterus off major blood vessels (prevents supine hypotensive syndrome)
Leopold's Maneuvers--If right-handed, stand on woman's right, facing her.
1. Identify fetal part that occupies the fundus. The head feels round, firm, freely movable, and palpable by ballottement; the breech feels less regular and softer. This maneuver identifies fetal lie (longitudinal or transverse) and presentation (cephalic or breech).
Leopold's Maneuvers
2. Using palmar surface of one hand, locate and palpate the smooth convex contour of the fetal back and the irregularities that identify the small parts (feet, hands, elbows). This maneuver helps identify fetal presentation.
Leopold's Maneuvers
3. With right hand, determine which fetal part is presenting over the inlet to the true pelvis. Gently grasp the lower pole of the uterus between the thumb and fingers, pressing in slightly. If the head is presenting and not engaged, determine the attitude of the head (flexed or extended).
Leopold's Maneuvers
4. Turn to face the woman's feet. Using both hands, outline the fetal head with the palmar surface of the fingertips. When the presenting part had descended deeply, only a small portion of it may be outlined. Palpation of the cephalic prominence helps identify the attitude of the head. If the cephalic prominence is bound on the same side as the small parts, this means that the head must be flexed and the vertex is presenting. If the cephalic prominence is on the same side as the back, this indicates that the presenting head is extended and the face is presenting.
Document fetal presentation, position, and lie and whether presenting part is flexed or extended, engaged, or free floating,
Examples of fetal vertex (occiput)
Occiput defined -- The back part of the skull. On the fetal head, it is used to determine the position of cephalic presentations in relation to the front, back, or side of the maternal pelvis.
Examples of fetal vertex (occiput)
ROP -- Right occipitoposterior
LOP -- Left occipitoposterior
ROT -- Right occipitotransverse
LOP -- Left occipitotransverse
ROA -- Right occipitoanterior
LOA -- Left occipitoanterior
Stages of Labor
premonitory
first stage
second stage
third stage
fourth stage
Stages of Labor
Labor is considered "normal" when the woman is at or near term, no complications exist, a single fetue presents by vertex, and labor is completed within 18 hours. The course of normal labor, which is remarkably constant, consists of (1) regular progression of uterine contractions, (2) effacement and progressive dilation of the cervix, and (3) progress in descent of the presenting part. Four stages of labor are recognized.
The first stage of labor
The first stage of labor is considered to last from the onset of regular uterine contractions to full dilation of the cervix. Commonly the onset of labor is difficult to establish because the woman may be admitted to the labor unit just before birth, and the beginning of labor may be only an estimate. The first stage is much longer than the second and third combined.
The first stage of labor
The first stage of labor has been divided into three phases: a latent phase, an active phase, and a transition phase.
The first stage of labor
During the latent phase, there is more progress in effacement of the cervix and little increase in descent.
The first stage of labor
During the active phase and the transition phase, there is more rapid dilation of the cervix and increased rate of descent of the presenting part.
The second stage of labor
The second stage of labor lasts from the time the cervix is fully dilated to the birth of the fetus. The second stage takes an average of 20 minutes for a multiparous woman and 50 minutes for a nulliparous woman.
The third stage of labor
The third stage of labor lasts from the birth of the fetus until the placenta is delivered. The placenta normally separates with the third or fourth strong uterine contraction after the infant has been born. After it has separated, the placenta can be delivered with the next uterine contraction. The duration of the third stage may be as short as 3 to 5 minutes, although up to 1 hour is considered within normal limits. The risk of hemorrhage increases as the length of the third stage increases.
The fourth stage of labor
The fourth stage of labor arbitrarily lasts about 2 hours after delivery of the placenta. It is the period of immediate recovery, when homeostasis is reestablished. It is an important period of observation for complications, such as abnormal bleeding.
The Seven Cardinal Movements of the Mechanism of Labor
The seven cardinal movements of the mechanism of labor that occur in a vertex presentation are engagement, descent, flexion, internal rotation, extension, external rotation (restitution), and finally birth by expulsion. Although these movements are discussed separately, in actuality, a combination of movements occurs simultaneously. For example, engagement involves both descent and flexion.
Engagement
When the biparietal diameter of the head passes the pelvic inlet, the head is said to be engaged in the pelvic inlet. In most nulliparous pregnancies, this occurs before the onset of active labor because the firmer abdominal muscles direct the presenting part into the pelvis. In multiparous pregnancies, in which the abdominal musculature is more relaxed, the head often remains freely movable above the pelvic brim until labor is established.
Descent
Descent refers to the progress of the presenting part through the pelvis. Descent depends on at least four forces: (1) pressure exerted by the amniotic fluid, (2) direct pressure exerted by the contracting fundus on the fetus, (3) force of the contraction of the maternal diaphragm and abdominal muscles in the second stage of labor, and (4) extension and straightening of the fetal body.
Degree of descent
The degree of descent is measured by the station of the presenting part. As mentioned, little descent occurs during the latent phase of the first stage of labor. Descent accelerates in the active phase when the cervix has dilated to 5 to 7 cm. It is especially apparent when the membranes have ruptured.
In a first-time pregnancy, descent is usually slow but steady; in subsequent pregnancies descent may be rapid.
Progress in descent
Progress in descent of the presenting part is determined by abdominal palpation (Leopold maneuvers) and vaginal examination until the presenting part can be seen at the introitus.
Flexion
As soon as the descending head meets resistance from the cervix, pelvic wall, or pelvic floor, it normally flexes, so that the chin is brought into closer contact with the fetal chest. Flexion permits the smaller suboccipitobregmatic diameter (9.5 cm) rather than the larger diameter to present to the outlet.
Internal Rotation
The maternal pelvic inlet is widest in the transverse diameter; therefore the fetal head passes the inlet into the true pelvis in the occipitotransverse position. The outlet is widest in the antereoposterior diameter, however; therefore for the fetus to exit, the head must rotate. Internal rotation begins at the level of the ischial spines but is not completed until the presenting part reaches the lower pelvis. As the occiput rotates anteriorly, the face rotates posteriorly.
Extension
When the fetal head reaches the perineum for birth, it is deflected anteriorly by the perineum. The occiput passes under the lower border of the symphysis pubis first, and then the head emerges by extension: first the occiput, then the face, and finally the chin.
Restitution and External Rotation
After the head is born, it rotates briefly to the position it occupied when it was engaged in the inlet. This movement is referred to as restitution. The 45-degree turn realigns the infant's head with her or his back and shoulders. The head can then be seen to rotate further. This external rotation occurs as the shoulders engage and descend in manuevers similar to those of the head. As noted earlier, the anterior shoulder descends first. When it reaches the outlet, it rotates to midline and is delivered from under the pubic arch. The posterior shoulder is guided over the perineum until it is free of the vaginal introitus.
Expulsion
After birth of the shoulders, the head and shoulders are lifted up toward the mother's pubic bone and the trunk of the baby is born by flexing it laterally in the direction of the symphysis pubis. when the baby has completely emerged, birth is complete, and the second stage of labor ends.
Physiological adaptations of pregnancy: Cardiovascular changes
During each contraction, an average of 400 mL of blood is emptied from the uterus into the maternal vascular system. This increases cardiac output by about 12% to 31% in the first stage and by about 50% in the second stage. The heart rate increases slightly. Changes in the woman's blood pressure also occur. Blood flow, which is reduced in the uterine artery by contractions, is redirected to peripheral vessels. As a result, peripheral resistance increases, and blood pressure increases. During the first stage of labor, uterine contractions cause systolic readings to increase by about 10 mm Hg; assessing blood pressure between contractions therefore provides more accurate readings. During the second stage, contractions may cause systolic pressures to increase by 30 mm Hg and diastolic readings to increase by 25 mm Hg, with both systolic and diastolic pressures remaining somewhat elevated even between contractions. Therefore the woman already at risk for hypertension is at increased risk for complications such as cerebral hemorrhage.
Valsalva maneuver
The woman should be discouraged from using the Valsalva maneuver (holding one's breath and tightening abdominal muscles) for pushing during the second stage. This activity increases intrathoracic pressure, reduces venous return, and increases venous pressure. The cardiac output and blood pressure increase and the pulse slows temporarily. During the Valsalva maneuver, fetal hypoxia may occur. The process is reversed when the woman takes a breath.
Physiological adaptations of pregnancy: Cardiovascular changes
Some peripheral vascular changes occur, perhaps in response to cervical dilation or to compression of maternal vessels by the fetus passing through the birth canal. Flushed cheeks, hot or cold feet, and eversion of hemorrhoids may result.
Physiological adaptations of pregnancy: Respiratory changes
Increased physical activity with greater oxygen consumption is reflected in an increase in the respiratory rate. Hyperventilation may cause respiratory alkalosis (an increase in pH), hypoxia, and hypocapnia (decrease in carbon dioxide). In the unmedicated woman in the second stage, oxygen consumption almost doubles. Anxiety also increases oxygen consumption
Physiological adaptations of pregnancy: Renal changes
During labor, spontaneous voiding may be difficult for various reasons: tissue edema caused by pressure from the presenting part, discomfort, analgesia, and embarrassment. Proteinuria of +1 is a normal finding because it can occur in response to the breakdown of muscle tissue from the physical work of labor.
Physiological adaptations of pregnancy: Gastrointestinal changes
During labor, gastrointestinal motility and absorption of solid foods are decreased, and stomach-emptying time is slowed. Nausea and vomiting of undigested food eaten after onset of labor are common. Nauses and belching also occur as a reflex response to full cervical dilation. The woman may state that diarrhea accompanied the onset of labor, or the nurse may palpate the presenceof hard or impacted stool in the rectum.
Physiological adaptations of pregnancy: Endocrine changes
The onset of labor may be triggered by decreasing levels of progesterone and increasing levels of estrogen, prostaglandins, and oxytocin. Metabolism increases, and blood glucose levels may decrease with the work of labor.
Accurate assessment of the mother and fetus during labor and birth depends on knowledge of these expected adaptations so that appropriate interventions can be implemented.
Physiological adaptations of pregnancy: Renal changes
During labor, spontaneous voiding may be difficult for various reasons: tissue edema caused by pressure from the presenting part, discomfort, analgesia, and embarrassment. Proteinuria of +1 is a normal finding because it can occur in response to the breakdown of muscle tissue from the physical work of labor.
Physiological adaptations of pregnancy: Gastrointestinal changes
During labor, gastrointestinal motility and absorption of solid foods are decreased, and stomach-emptying time is slowed. Nausea and vomiting of undigested food eaten after onset of labor are common. Nauses and belching also occur as a reflex response to full cervical dilation. The woman may state that diarrhea accompanied the onset of labor, or the nurse may palpate the presenceof hard or impacted stool in the rectum.
Physiological adaptations of pregnancy: Endocrine changes
The onset of labor may be triggered by decreasing levels of progesterone and increasing levels of estrogen, prostaglandins, and oxytocin. Metabolism increases, and blood glucose levels may decrease with the work of labor.
Accurate assessment of the mother and fetus during labor and birth depends on knowledge of these expected adaptations so that appropriate interventions can be implemented.