Unit 6 L&D Part 1
Labor & Delivery Study Notes
What Causes Labor?
Research indicates that hormones play a major role in the onset of labor. The key hormones are:
Progesterone: Promotes uterine muscle relaxation. Its levels decrease towards the end of pregnancy, leading to stimulated contractions as estrogen levels rise.
Estrogen: Enhances uterine sensitivity, making the uterus more responsive to contractions.
Oxytocin: Stimulates uterine contractions, contributing to labor progression.
Prostaglandins: Levels increase towards the end of pregnancy; they stimulate contractions and help soften the cervix to prepare for delivery.
Premonitory Signs of Labor
These signs often precede labor:
Lightening: The fetus descends further into the pelvis, often relieving pressure on the diaphragm.
Braxton Hicks contractions: Irregular, mild contractions also known as false labor.
Cervical changes: Softening (ripening) of the bottom of the uterus occurs.
Bloody show: Expulsion of the mucous plug that was in the cervix.
Spontaneous rupture of membranes: Often referred to as water breaking.
Burst of energy (Nesting): Increased physical activity or a desire to prepare for the baby.
Weight loss of 1-3 lbs.: Likely due to loss of water weight.
The “4 P’s”: Critical Factors of Labor
The four critical factors affecting labor include:
Powers: Relates to the strength and effectiveness of contractions and maternal effort.
Passage: Refers to pelvic size, specifically the diameters of the pelvis.
Passenger: Refers to the fetus, including the fetal skull, position (attitude, lie, presentation), and station within the pelvis.
Psyche: Influences from parental preparation (e.g., childbirth classes), past labor experiences, emotional and physical factors, stress responses, support systems, and cultural influences.
Anatomy of the Uterus
Myometrium: The primary muscular layer of the uterus responsible for contractions.
Fundus: The uppermost part of the uterus.
Cervix: The lower opening of the uterus that dilates during labor, with dilatation measured from 0 to 10 cm.
Endometrium: The inner lining of the uterus that thickens during the menstrual cycle and is shed during menstruation.
Cervical canal: The passage leading from the cervix to the vagina.
Breakdown of Uterine Structure
The uterus is mainly composed of the myometrium, providing the contraction force necessary for labor.
The fundus (top of the uterus) is where contractions initiate, progressively tightening, peaking, and then relaxing.
The cervix, or the opening of the uterus, consists of an internal and external os, both of which need to dilate for labor to proceed.
Assessing Contractions
Contractions include three main phases:
Increment: The beginning phase of contraction.
Peak (Acme): The point of highest intensity.
Decrement: The relaxation phase after the peak.
Contraction Cycle Components
Frequency: Measured from the start of one contraction to the start of the next. Optimal frequency is every 2-3 minutes.
Duration: The length of a contraction measured from the start to the end of the contraction.
Intensity: The strength of the contraction felt by palpation on the fundus.
Interval (Resting Tone): The time between contractions, critical for fetal oxygen and nutrient exchange, ideally about one minute, allowing the uterus to rest.
Cervical Changes During Labor
Cervical dilation is measured in centimeters, with full dilation at 10 centimeters indicating that the cervix is open enough for the baby to pass through.
Effacement: The thinning and shortening of the cervix during labor, estimated in percentage from 0% (long and thick) to 100% (very thin).
Visualization of effacement can be imagined as a turtle neck sweater stretching to accommodate a head.
The 2nd “P”: Passage
Refers to the bony pelvis, where key measurements, such as the ischial spines, are defined. When the fetus’s head is at the ischial spine level, it is in “Zero station,” indicating descent in the pelvis.
Presentation and Station
When the fetus’s head is 1 cm above the ischial spines, it is in a -1 station; below is +1 station, indicating the descent of the fetus.
The 3rd “P”: Passenger (the fetus)
Fetal Lie: Orientation of the fetus in the uterus (longitudinal vs. transverse).
Attitude: The flexion of the fetal body parts to one another.
Fetal Presentation: The part of the fetus that is foremost in the birth canal.
Fetal Position: The location of the presenting part in relation to the maternal pelvis.
Passenger: Fetal Position
Fetal position is described using a three-letter system:
The first letter indicates the side of the pelvis (R for right, L for left).
The second letter specifies the reference point (O = occiput, S = sacrum).
The third letter indicates the location (A = anterior, P = posterior, T = transverse).
Leopold’s Maneuvers
Leopold’s Maneuvers consist of four steps to determine fetal position through abdominal examination:
Palpate fundus: Determine if the head or breech is present.
Palpate sides of uterus: Identify small parts (arms and legs) and the back’s location.
Palpate suprapubic: Determine if presenting part is engaged.
Palpate lower uterine segment: Assess fetal flexion or extension (sensitive to breech).
Auscultating Fetal Heart Rate
Fetal heart tones can be located during Leopold's maneuvers, typically ranging between 120-160 bpm.
Heartbeat will be loudest in specific areas based on fetal position (vertex vs. breech).
The 4th “P”: Psyche
Factors influencing maternal responses during labor include parental preparation, previous labor experiences, emotional and physical states, stress responses, support systems, and cultural influences.
Anxiety and fear may decrease coping abilities and inhibit uterine contractility and blood flow, creating a fear-tension-pain cycle.
Stages of Labor
Labor and delivery are divided into four stages:
Stage 1: Dilation Stage includes three phases (latent, active, and transition).
Stage 2: Pushing Stage, where the infant is born.
Stage 3: Placental Stage, from the birth of the baby to delivery of the placenta.
Stage 4: Recovery Stage, marking the beginning of the postpartum period.
Stage One: Dilation Stage
Latent Phase (0-3 cm): Mild contractions are felt, effacement gradually occurs, and the psychological state tends to be excited and talkative.
Active Phase (4-7 cm): Contractions are stronger; most effacement happens here, and the psychological state turns to anxious and restless.
Transition Phase (8-10 cm): Rapid dilation with a potential loss of control; characterized by strong, frequent contractions and an urge to push.
Stage Two: Pushing Stage
The mother pushes once completely dilated; cardinal movements of the fetus during delivery include descent, engagement, flexion, internal rotation, extension, external rotation, and expulsion.
Mnemonic: "Does every female in rural England eat red eggplant?"
Stage Three: Placental Stage
Starts with the baby’s birth and ends with the placenta being expelled, which can cause a gush of blood and a change in the shape of the uterus.
Stage Four: Recovery
The initial two hours postpartum are critical, marking the start of the recovery and postpartum period.
Possible Nursing Diagnoses Associated with Labor
Deficient Knowledge: Labor and delivery process understanding.
Acute Pain: Related to labor process.
Anxiety: Emotional state during labor.
Risk for Injury: Maternal and fetal risks during labor.
Learning Objectives:
1. Examine the common theories explaining the onset and continuation of labor.
2. Identify the premonitory signs of labor.
3. Differentiate between true and false labor.
4. Describe the critical factors that influence the laboring process: passenger, passage,
powers, and psychological impact.
5. Evaluate the progress of the woman in labor, identifying the stage /phases of labor
and critical events / nursing management in each stage.
6. Differentiate the maternal physiological and psychological changes occurring during
each stage of labor.