Components of Labor 4Ps in Labor A. Passage- pelvis of the mother -2 pelvic measurements1.diagonal conjugate- anterior-posterior dm of the inlet
-narrowest dm outlet -normal 10.5- 12 cm 2.transverse diameter - anterior dm of the outlet
-narrowest dm inlet -normal 8.5-10cm
B. Passenger- fetus -widest diameter of the fetus is HEAD
STRUCTURE OF THE FETAL SKULL Cranium- the uppermost of the skull -composed of 8 bones:
4 Important Bones: 1 frontal 2 parietal 1 occipital Frontal bone- referred to as the SINCIPUT Occipital bone- referred to as the OCCIPUT
4 Other bones of the skull: 1 sphenoid 1 ethmoid bone 2 temporal bones
SUTURE LINES- lines where bones of the skull meet. -is important in the birth because they allow the crania l bones to move & overlap, thus molding/diminishing molding/diminishing the size of the skull so it i t can pass through the birth canal more r eadily.
3 Kinds Sutures: 1.
Sagittal suture-joins the 2 parietal bones
2.
C oronal suture-joins the frontal bone and the 2 parietal bones
3.
Lambdoid suture-joins the occipital bone and the 2 pa rietal bones
FONTANELLES- a membrane-covered spaces -found at the junction of the main suture lines. -fontanelle spaces compress during birth to aid in molding of the manual e xamination of the cervix after it has dilated during labor.
2 kinds of Fontanelles: 1. Anterior fontanelle(sometimes referred to as the bregma)
- bet. The coronal &sagittal sutures - anteroposterior dm measures approx. 3-4cm& its transverse dm 2-3 cm 2. Posterior fontanelle- lies at the junction of the lambdoidal & sagittal sutures.
-it is smaller than the anterior fontanelle measuring approx. 2cm across its widest part. VERTEX- is
the space between the 2 fontanelles.
DIAMETER OF THE FETAL SKULL Transverse diameter- smaller dm of the maternal pelvis *Suboccipitobregmatic diameter - the narrowest dm (approx. 9.5cm) from the inferior aspect of the occiput to the center of the anterior fontanelle.
*Occipitofrontal diameter - (approx. 12cm) from the bridge of the nose to the occipital prominence. *Occipitomental diameter - the widest anteroposterior dm
(approx. 13.5cm) from the chin to the
posterior fontanelle. *Biparietal
diameter- (approx. 9.25cm) the narrowest diameter.
MOLDING- is the change in shape of the fetal skull produced by the force of uterine contractions pressing the vertex against the not yet dilated cervix.
FETAL PRESENTATION AND POSITION Attitude- describes the degree of flexion the fetus assumes during labor/ the relation of the fetal parts to each other. 1. Complete/ full flexion- chin touches the sternum -vertex cephalic presentation 2. Moderate flexion- the chin is not touching the chest but is in an alert or military position. 3. Partial extension- presents the brow of the head to the birth canal 4. Poor flexion - the back is arched, the neck extended & the fetus is in complete e xtension, presenting the occipitomental dm of the head to the b irth canal.
Engagement- refers to the settling of the presenting part of the fetus far enough into the pelvis to be at the ischial spines a midpoint of the pelvis.
Station- refers to the relationship of the presenting part of the fe tus to the level of the ischial spines. -station 0 level of the head of the fetus is in the ischial spine -above the ischial spine (-) - below the ischial spine (+)
Lie- is the relationship bet. the long axis of the womens body & the long axis of t he fetal body
Types of Fetal Presentation 1. Cephalic presentation- the head is the body part that is contact the cervix. st
2. Breech presentation- either the buttocks/ feet are the 1 body parts to contact the cervix. 3. Shoulder presentation- in a transverse lie,the fetus is lying horizontally in the pelvis so that its long axis is perpendicular to that of the mother.
Possible Fetal Presentations Vertex presentation(occiput)
LOA, left occipitoanterior LOP, left occipitoposterior LOT, left occipitotransverse ROA, right occipitoanterior
ROP, right occipitoposterior ROT, right occipitotransverse
Breech presentation(sacrum) LSaA, left sacroanterior LSaP, left sacroposterior LSaT, left sacrotransverse RSaA, right sacroanterior RSaP, right sacroposterior RSaT, right sacrotransverse
Face presentation(mentrum) LMA, left mentoanterior LMP, left mentoposterior LMT, left mentotransverse RMA, right mentoanterior RMP, right mentoposterior RMT, right mentotransverse
Shoulder presentation(acromion process) LAA, left scapuloanterior LAP, left scapuloposterior RAA, right scapuloanterior RAP, right scapuloposterior
Mechanism of Labor- also known as the cardinal movement of labor. 1. Descent- the downward movt of the biparietal diame ter of the fetal head within the pelvic inlet. 2. Flexion- fetal head bend forward on to the chest. 3. Internal rotation- head enters the pelvis with the fetal anteroposterior head diameter is in a diagonal or transverse position. 4. Extension- the back of the neck stops beneath t he pubic arch & acts as a pivot for the rest of the head. 5. External rotation-head rotates to the diagonal or transverse position. 6. Expulsion- once the shoulder are born, the re st of the fetal body is easily & smoothly born.
C. Powers of Labor- supplied by the fundus of the uterus, are implemented by uteri ne contractions, a process that causes cervical dilatation & then expulsion of the fetus from the uterus.
Uterine contractions a.Origins-like cardiac contractions, labor contraction be gin at a pacemaker point located in
the myometrium near one of the uterotubal junctions.
3 Phases of Uterine contractions 1. Increment- intensityof contraction increases. 2. Acme- strongest contraction. 3. Decrement- intenstityof contraction decreases.
b. C ontour changes- as the labor contractions progress and become r egular & strong, the
uterus gradually differentiates itself into two distinct functioning areas. -the upper portion becomes thicker & active, preparing it to exert the strength necessary to expel the fetus when the expulsion phase of labor is reached. - the lower segment becomes thin-walled,supple,and passive, so the fetus can be pushed out of the uterus easily. Physiologic retraction ring- the boundary bet. the 2 portions becomes marked by a ri dged on the inner uterine surface. Pathologic retraction ring/ Bandls ring- it is a danger sign that signifies impending rupture of the lower uterine segment if the obstruction to labor is not re lieved. c. C ervical changes 1.
Effacement - shortening & thinning of the cervical canal
2.
dilatation- enlargement of the cervical canal fromthe opening of the few millimetres
wide to one large enough (approx. 10cm) to permit passage of the fetus.
D. Psyche- refers to the psychological state/ feelings that women bring into labor with them.
