Any hollow body organ when stretched to capacity will necessarily contract and empty
Oxytocin theory
Labor, being considered a stressful event, stimulates the hypophysis to produce oxytocin from the posterior pituitary gland. Oxytocin causes contraction of the smooth muscles of the body, e.g., uterine muscles
Progesterone Deprivation theory
Progesterone, being the hormone designed to promote pregnancy, is believed to inhibit uterine motility. Thus, if its amount decreases, labor pains occur
Prostaglandin theory
Initiation of labor is said to result from the release of arachidonic acid produced by steroid action on lipid precursors. Arachidonic acid is said to increase prostaglandin synthesis which, in turn, causes uterine contractions
Theory of Aging Placenta
Because of the decrease in blood supply, the uterus contracts
Essential Factors of Labor (5Ps)
Passages
Power
Passenger
Person
Position
Passages
Serves as birth canal
Proves attachment to muscles, fascia and ligaments
Supports uterus during pregnancy
Provides protection to the organs found within the pelvic cavity
Types of Pelvis
Gynecoid
Android
Platypelloid
Anthropoid
Gynecoid pelvis
Normal female type of pelvis, most ideal for childbirth, round shape, found in 50% of women
Android pelvis
Male pelvis, presents the most difficulty during childbirth, found in 20% of women
Platypelloid pelvis
Flat pelvis, rarest, occurs to 5% of women
Anthropoid pelvis
Apelike pelvis, deepest type of pelvis found in 25% of women
Division of Pelvis
False Pelvis
True Pelvis
False Pelvis
Provides and directs
True Pelvis
The tunnel
Inlet or Pelvic Brim
Entrance to true pelvis
Anteroposterior Diameters of Pelvis
Diagonal Conjugate
Obstetric Conjugate
True Conjugate
Diagonal Conjugate
Midpoint of sacral promontory to the lower margin of symphysis pubis (12.5 cm)
Obstetric Conjugate
Midpoint of sacral promontory to the midline of symphysis pubis (11 cm)
True Conjugate
Midpoint of sacral promontory to the upper margin of symphysis pubis (11.5 cm)
Pelvic Canal
Situated between inlet and outlet, designed to control the speed of descent of the fetal head
Outlet
Most important diameter of the outlet
Powers (3I's)
Involuntary - not within the control of the parturient
Intermittent - alternating contraction and relaxation
Involves discomfort (compression, stretching and hypoxia)
Phases of Uterine Contractions
Increment/Crescendo
Acme/Apex
Decrement/Decrescendo
Intensity
Strength of uterine contraction
Intensity Levels
Mild - slightly tensed fundus
Moderate - firm fundus
Strong - rigid, board like fundus
Frequency
Rate of uterine contraction, measured from the beginning of a contraction to the beginning of the next contraction
Duration
Length of uterine contraction, measured from the beginning of a contraction to the end of the same contraction
Interval
Measured from the end of contraction to the beginning of the next contraction
Blood Pressure
Should not be taken during a contraction as it tends to increase. Because no blood supply goes to the placenta during a contraction, all the blood is in the periphery that is why there is increased BP during uterine contractions.
BP readings should be taken at least every half hour during active labor
When a woman in labor complains of a headache, the first nursing action is to take BP. If it is normal, it is only stress headache; if the BP is increased, refer immediately to the doctor (it could be a sign of toxemia)
Fetal Heart Rate (FHR)
Should not be mistaken for uterine soufflé (synchronizes with maternal pulse rate)
Normally 120 to 160 per minute
Should not be taken during a uterine contraction because it tends to decrease. Compression of the fetal head when the uterus contracts stimulate the vagal reflex which, in turn, causes bradycardia
Should be taken every hour during the latent phase of labor, every half hour during the active phase and every 15 minutes during the transition period
For any abnormality in FHR, the initial nursing action is to change the mother's position
Signs of fetal distress: Bradycardia (FHR less than 100/minute) or tachycardia (FHR more than 180/minute), Meconium - stained amniotic fluid in non - breech presentation, Fetal thrashing - hyperactivity of the fetus as it struggles for more oxygen
Head
Biggest part of the fetal body
Always the presenting part
Turn to present smallest diameter
Cranial Bones
1 frontal bone
2 parietal bone
1 occipital bone
2 temporal bone
1 sphenoid bone
1 ethmoid bone
Suture Lines
Allow skull bones to overlap (molding) and for further brain development
Suture Lines
Sagittal Suture
Frontal Suture
Coronal Suture
Lambdoidal Suture
Anterior Fontanel or Bregma
Intersection of suture lines, diamond shaped, closes between 12 - 18 months, 3 x 4 cm
Most important transverse diameter, greatest diameter presented to the pelvic inlet's AP and at the outlet's TD, average measurement is 9.5 cm
Suboccipitobregmatic Diameter
Smallest anteroposterior diameter, fully flexed (presenting part), measured from the inferior aspect of occiput to the anterior fontanel, average measurement is 9.5 cm