laboranddelivery Mr. Schmidt
Summit Career College

Theories of Labor Mechanical and hormonal changes

Mechanical theory (involves uterine stretching) When a hollow organ reaches it s maximum capacity it will spontaneously contract/empty.

Hormonal theories (based on an increase or decrease in hormones) An incease in hormones triggers labor/decrease hormones triggers labor.

Signs of impending labor

Lightening 2 weeks before onset of labor, fetus "drops" into true pelvis; patient is able to breath easier, also encounters frequent urination.

Burst of energy backache and contraction of uterus (false labor aka Braxton Hicks)irregular.

Leakage sudden outflow of fluid from vagina, may be urine or amniotic sac, the nurse needs to chek with nitrazine paper if paper turns blue + for amniotic fluid. If fuptures before labor --> increase in chance of infection. If not in labor within 24 hur afrter the bag of waters (BOW) rupture, monitor for infection

An increased vaginal drainage --> blood tinged mucus (bloody show) is observed. (The show is the mucous which has occluded the opening of the cervix during pregnancy.

Comparison of false labor to true labor

False Duration of contraction remains the same, the contractions vary in length and intensity. the periods between contractions are long/irregular. stops with ambulation or position change. Contractions are felt in the back; the cervix may soften, thee is no change in dilation/effacement.

True labor Contractions are regular, closer together, increase in intensity and last longer. They also become stronger with ambulation. Cervix softens, effaces, dilates. Show is present in true labor.

The 4 P's of the Pregnancy Process

Passageway -  pelvis and soft tissue
Passenger - fetus/placenta
Powers - contraction/voluntary effort
Position - standing, walking, side lying

Female pelvis
Passaweway Functions to suport uterus/fetus during late months of pregnancy. Two sections with iomaginary lines. Linea terminalis or pelvic inlet. The head has to pass through for delivery.

Means of evaluating size of true pelvis
Palpation - externally MD uses pelvimeter to determine distance between ischial tuberosities.
Internally - palpate bony prominences to determine how adequate the pelvis is.
ultrasonography - shows the fetal grwowth/multiple births/placental location/abnormal presentation.
Soft tissues that comprise the passageway - Uterine tissues, cervical tissues, vagina (increased blood supply), perineum.

Fetal skull - Largest part of body, the bones are not figidly joined (fused), so they move and overlap.
Molding (reshaping of skull bones in response to pressure against the maternal pelvis)occurs. The major pones are: FRONTAL (2) PARIETAL (2) TEMPORAL (2) AND OCCIPUT(1). These are joined together by fontanels.
The anterior fontanel (bregma) is larger and diamond shape and is formed by 4 bones. The posterior fontanel is smaller and formed by 3 bones.

Fetal attitude This is the relationship of body parts one to another. The ideal attitude is flexion.

fetal lie The relationship of the cephalocaudal(head to buttocks) axis of fetus to cephalocaudal axis of mother.

Fetal presentation The cephalic presentation occurs approximately 96% of the time. The other potential presentations include the vertex (region between the fontanels), brow, face, and mentus (chin).

The fetal position is determined by inspection, palpation (Leopold's maneuver). The most common position is the left occiput anterior (LOA), where the back points toward the left anteror segment of the pelvis.
the ideal position is the longitudinal lie. This is due to the fact that the fetal skull bones must be able to mold to the maternal pelvis.

The normal range for the fetal cardiac rate is from 120-160 bpm. Any increase or decrease of 30 beats/minute,from these parameters can be interpreted as fetal distress which can lead to fetal demise.

Powers - involuntary and voluntary maternal contractions.
Uterine contractions - in early labor contractions occur 15-30 minutes apart and last for approximatly 20-35 seconds. In the most active stag the contractions occur 2-3 minutes apart and last approximatly 60-80 seconds.
EDach contraction has 3 parts - the increment, Apex (where optimal force is exerted and the decrement (muscular relaxation occurs).
A contractijon occurs when the uterine cavitgy decreases in size and forces the BOW against the cervix. This combination of actions efface and dilates the cervix.
The term Nulliparous means that effacement preceds dilation. Multiparas is when the effacement and dilation occurs at the same time. When the patient fees the urge to push or dear down and states that the she has the urge to defecate, this is the voluntary  pushing step.

Process Mechanism of labor

Engagement - the descent (downard progress of presenting part).
Station - the relationship of presenting part to ischial spines of the pelvis (measured in cm above or below the spines).
Flexion - is the internal rotation, extension (occiput passes under symphysis pubis). Moves to realign with body and shoulders, external rotation(shoulders and body moves through); expulsion.


Frist stage - Starts with onset of REGULAR contractons, ends with complete dilation and has 3 phases:
Early latent phase - Pt is alert/talkative/pain mild/receptive to coaching on breathing techniqes.
Mid (active) phase - Less talkative/focus on breathing techniques. Pain intensity increases, pain management without pain meds.
Transition Time of deep focus/no communication.

Second stage - Complete dilation at 10 cm and ends with birth.
Anesthesia and an episiotomy (midline incision) are common. Airway is established and the umbilical cord is clamped.

Third stage Begins with delivery and ends with expulsion of placenta.

Separation of placenta/expulsion. When the placenta detaches, there is a sudden outporing of blood, and the cord lengthens. The uterus becomes round and firm. Ocytocin(pitocin) may be given --> uterus to contract.

Fourth stage - Stabilization
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OB lecture 1
Last updated  2008/09/28 05:18:04 PDTHits  185