Week 7 Flashcards
Labor normally begins when a fetus is ———to cope with extrauterine life yet not too large to cause __________with birth.
sufficiently mature
mechanical difficulty
results in release of prostaglandins
Uterine muscle stretching
which stimulates the release of oxytocin from the posterior pituitary
Pressure on the cervix
which works together with prostaglandins to initiate contractions
Oxytocin stimulation
(increasing estrogen in relation to progesterone, which is interpreted as progesterone withdrawal)
Change in the ratio of estrogen to progesterone
which triggers contractions at a set point
Placental age,
which reduces progesterone formation and increases prostaglandin formation
Rising fetal cortisol levels,
which stimulates contraction
Fetal membrane production of prostaglandin
woman often experiences subtle signs that signal labor is imminent. It is important to review these with women during the last trimester of pregnancy so they can more easily recognize beginning signs.
PRELIMINARY SIGNS OF LABOR
lightening, or descent of the fetal presenting part into the pelvis, occurs approximately 10 to 14 days before labor begins.
primiparas
related to an increase in epinephrine release initiated by a decrease in progesterone produced by the placenta. This additional epinephrine prepares a woman’s body for the work of labor ahead.
Increase in Level of Activity
As___________ level falls, body fluid is more easily excreted from the body. This increase in urine production can lead to a weight loss between 1 and 3 pounds.
progesterone
the cervix becomes still softer (described as “butter-soft”), and it tips forward.
Ripening of the cervix
an internal announcement that labor is very close at hand.
Ripening of the cervix
Signs of true labor involve_____ and______ changes.
uterine
cervical
The surest sign that labor has begun
involuntary and come without warning, their intensity can be frightening in early labor
Uterine Contraction
Helping a woman appreciate that she can predict when her next one will occur and therefore can control the degree of discomfort she feels by using ____________________offers her a sense of well-being.
breathing exercises
As the cervix softens and ripens, the mucus plug that filled the cervical canal during pregnancy(operculum) is expelled.
Show
This blood, mixed with mucus, takes on a pink tinge and is referred to as
show or bloody show.
Labor may begin with_____________________, experienced either as a sudden gush or as scanty, slow seeping of clear fluid from the vagina.
rupture of the membranes
Two risks associated with ruptured membranes are
which could cut off the oxygen supply to the fetus
intrauterine infection and prolapse of the umbilical cord
successful labor depends on four integrated concepts:
Passage
Passenger
Power
Psychological
the passage
woman’s pelvis
passenger
fetus
The powers of labor
uterine factors
psychological outlook
positive experience.
refers to the route a fetus
must travel from the uterus through the cervix and vagina to the external perineum.
passage
Two pelvic measurements are important to determine the adequacy of the pelvic size:
diagonal conjugate
transverse diameter
part least likely to be able to pass through the pelvic ring.
head
change in the shape of the fetal skull produced by the force of uterine contractions pressing the vertex of the head against the not-yet-dilated cervix.
Molding
refers to the settling of the presenting part of a fetus far enough into the pelvis to be at the level of the ischial spines, a midpoint of the pelvis.
Engagement
refers to the relationship of the presenting part of a fetus to the level of the ischial spines.
Station
When the presenting fetal part is at the level of the___ spines, it is at a 0 station
ischial
If the presenting part is above the spines, the distance is measured and described as_________ stations, which range from 1 to 4 cm.
minus
If the presenting part is below the ischial spines, the distance is stated as______ stations (+1 to +4)
plus
describes the degree of flexion a fetus assumes during labor or the relation of the fetal parts to each other
Fetal Attitude
A fetus in good attitude is in(1):
the spinal column is bowed (2)
, the head is flexed forward so much that the chin touches the(3)
, the arms are flexed and folded on the chest, the thighs are flexed onto the abdomen, and the calves are pressed against the (4) aspect of the thighs.
- complete flexion
- forward
- sternum
- posterior
This normal “fetal position” is advantageous for birth because it helps a fetus present the smallest anteroposterior diameter of the skull to the pelvis and also because it puts the whole body into an____________ shape, occupying the smallest space possible.
ovoid
A fetus is in moderate flexion if the chin is not touching the chest but is in an alert
military position”.
means that the widest part of the fetus (the biparietal diameter in a cephalic presentation; the intertrochanteric diameter in a breech presentation) has passed through the pelvis inlet or the pelvic inlet has been proved adequate for birth.
Descent
the relationship between the long (cephalocaudal) axis of the fetal body and the long (cephalocaudal) axis of a woman’s body; in other words, whether the fetus is lying in a horizontal (transverse) or a vertical (longitudinal) position
Fetal Lie
the most frequent type of presentation, occurring as often as 95% of the time. With this type of presentation, the fetal head is the body part that will first contact the cervix
Cephalic Presentation
The four types of cephalic presentation
vertex, brow, face, and mentum
The four types of cephalic presentation
vertex, brow, face, and mentum
means that either the buttocks or the feet are the first body parts that will contact the cervix
occur in approximately 3% of births and are affected by fetal attitude.
Breech Presentation
Three types of breech presentation
complete, frank, and footling
In a transverse lie, a fetus lies horizontally in the pelvis so that the longest fetal axis is perpendicular to that of the mother.
Shoulder Presentation
Leg folded with feet at the level of the baby’s bottom
Complete breech
One or both feet point down so the legs would emerge first
Footling breech
Legs point up with feet by the baby’s head so the bottom emerges first
Frank breech
Position is the relationship of the presenting part to a specific quadrant of a woman’s pelvis.
FETAL POSITION
Passage of a fetus through the birth canal involves several different position changes to keep the smallest diameter of the fetal head (in cephalic presentations) always presenting to the smallest diameter of the pelvis.
MECHANISM OF LABOR
Passage of a fetus through the birth canal involves several different position changes to keep the smallest diameter of the fetal head (in cephalic presentations) always presenting to the smallest diameter of the pelvis.
MECHANISM OF LABOR
These position changes are termed the cardinal movements of labor:
descent, flexion, internal rotation, extension, external rotation, and expulsion.
the downward movement of the
biparietal diameter of the fetal head to within the pelvic inlet.
occurs when the fetal head extrudes beyond the dilated cervix and touches the posterior vaginal floor.
occurs because of pressure on the fetus by the uterine fundus. The pressure of the fetal head on the sacral nerves at the pelvic floor causes the mother to experience a pushing sensation.
may be aided by abdominal muscle contraction as the woman pushes.
Descent
As descent occurs and the fetal head
reaches the pelvic floor, the head bends forward onto the chest, making the smallest anteroposterior diameter (the suboccipitobregmatic diameter) present to the birth canal.
Flexion
During descent, the head enters the pelvis
with the fetal anteroposterior head diameter (suboccipitobregmatic, occipitomental, or occipitofrontal, depending on the amount of flexion) in a diagonal or transverse position. The head flexes as it touches the pelvic floor, and the occiput rotates to bring the head into the best relationship to the outlet of the pelvis (the anteroposterior diameter is now in the anteroposterior plane of the pelvis). This movement brings the shoulders, coming next, into the optimal position to enter the inlet, putting the widest diameter of the shoulders,
Internal Rotation
As the occiput is born, the back of the neck stops beneath the pubic arch and acts as a pivot for the rest of the head.
Extension
almost immediately after the head of the infant is born, the head rotates (from the anteroposterior position it is assumed to enter the outlet) back to the diagonal or transverse position of the early part of labor. This brings the aftercoming shoulders into an anteroposterior position, which is best for entering the outlet. The anterior shoulder is born first, assisted perhaps by downward flexion of the infant’s head.
External Rotation
Once the shoulders are born, the rest of the baby is born easily and smoothly because of its smaller size. This movement,
Expulsion
This is the force supplied by the fundus of the uterus, implemented by uterine contractions, a natural process that causes cervical dilatation and then expulsion of the fetus from the uterus. After full dilatation of the cervix, the primary power is supplemented by use of the abdominal muscles. It is important for women to understand they should not bear down with their abdominal muscles until the cervix is fully dilated. Doing so impedes the primary force and could cause fetal and cervical damage
effective powers of labor
A contraction consists of three phases:
increment, when the intensity of the contraction increases;
the acme, when the contraction is at its strongest;
and the decrement, when the intensity decreases
Even more marked than the changes in the body of the uterus are two changes that occur in the cervix: effacement and dilatation
Cervical Changes
is shortening and thinning of the cervical canal. Normally, the canal is approximately 1 to 2 cm long. With effacement, the canal virtually disappears.
Effacement
refers to the enlargement or widening of the cervical canal from an opening a few millimeters wide to one large enough (approximately 10 cm) to permit passage of a fetus.
Dilatation
psychological state or feelings that a woman brings into labor. For many women, this is a feeling of apprehension or fright. For almost everyone, it includes a sense of excitement or awe.
PSYCHE
