Chapter 8 The Labor Process

Four Essential Components of Labor The Four Ps of Labor Passageway Passenger Powers Psyche Problematic areas influence labor negatively

Passageway Consists of bony pelvis, soft tissues Bony pelvis False pelvis The flared upper portion of the bony pelvis Not part of the bony passageway True pelvis The portion of the pelvis below the linea terminalis Consists of the inlet, midpelvis, and outlet

Passageway (cont.) Pelvic shape Gynecoid Most favorable for a vaginal birth Rounded shape Anthropoid Elongated shape Android Heart-shaped

Passageway (cont.) Pelvic shape (cont.) Platypelloid Flat in its dimensions Pelvic dimensions Most important is obstetric conjugate Soft tissues Cervix Vagina

Question State whether the following statement is true or false. The gynecoid pelvis is the most favorable for a vaginal birth.

Answer True Rationale: The gynecoid pelvis is most favorable for a vaginal birth.

Passenger Fetal skull Most important in relation to labor and birth Molding is overlap of bones Fetal accommodation to the passageway Fetal lie Longitudinal lie: Long axis of the fetus is parallel to maternal long axis Oblique lie: Between longitudinal and transverse lie

Passenger (cont.) Fetal lie (cont.) Transverse lie Long axis of fetus is perpendicular to maternal long axis

Passenger (cont.) Fetal presentation Foremost part of the fetus that enters the pelvic inlet Three main presentations Head: Cephalic presentation Feet or buttocks: Breech presentation Shoulder: Shoulder presentation

Passenger (cont.) Fetal attitude Relationship of fetal parts to one another Flexion (ovoid shape) Most favorable for vaginal delivery Military (no flexion or extension) Brow or frontum (partial extension) Face (full extension)

Passenger (cont.) Fetal position Relationship of reference point on presenting part to quadrants of maternal pelvis First letter/designation: Refers to side of maternal pelvis toward which presenting part is facing Second letter/designation: Reference point on presenting part Third letter/designation: Specifies direction presenting part is facing Anterior; posterior; transverse

Passenger (cont.) Fetal station: Relationship of presenting part to ischial spines Zero station Presenting part is at the level of the ischial spines Minus station Presenting part is above the ischial spines Plus station Presenting part is below the ischial spines

Powers Phases of involuntary uterine contraction Increment Building up of the contraction – longest phase Acme Peak of the contraction Decrement Letting-up phase Relaxation period Rest period between contractions

Powers (cont.) Descriptors of contractions Frequency: How often the contractions are occurring Measured by counting time interval from beginning of one contraction to beginning of following contraction Duration: Interval from beginning of a contraction to its end Intensity: Strength of the contraction

Question Fetal attitude refers to the relationship of fetal parts to each other. Which fetal attitude is most favorable to a vaginal birth? a. Extension b. Flexion c. Military d. Hyperextension

Answer b. Flexion Rationale: The most common, most favorable attitude for a vaginal birth, is an attitude of flexion, also called a vertex presentation.

Psyche Factors impacting the psyche of a laboring woman Current pregnancy experience Previous birth experiences Expectations for current birth experience Preparation for birth Presence and support of birth companion Culture

Process of Labor Onset of labor Theories regarding labor onset Progesterone withdrawal theory Oxytocin theory Prostaglandin theory Maternal and fetal factors Cascade effect

Process of Labor (cont.) Anticipatory signs of labor Lightening or sense that the baby has “dropped” Increased frequency, intensity of Braxton Hicks contractions Gastrointestinal disturbances Expelling the mucus plug Feeling a burst of energy Clinical signs Ripening (softening) and effacement (thinning) of the cervix

Process of Labor (cont.) Differences between false and true labor False (prodromal) labor Increase in Braxton Hicks contractions without cervical changes Can be uncomfortable True labor Progressive dilation and effacement of cervix

Mechanisms of a Spontaneous Vaginal Delivery Cardinal movements (mechanisms of delivery) Engagement Descent Flexion Internal rotation Extension External rotation Expulsion

Stages and Duration of Labor First stage: Dilation Early labor (latent phase) Active labor (active phase) Transition (transition phase) Second stage: Birth Third stage: Delivery of placenta Fourth stage: Recovery

Question Which stage of labor is birth? a. First stage b. Second stage c. Third stage d. Fourth stage

Answer b. Second stage Rationale: The second stage begins when the cervix is dilated fully and ends with the birth of the infant.

Maternal and Fetal Adaptation to Labor Maternal physiologic adaptation Increased demand for oxygen during the first stage of labor Increased heart rate Increased cardiac output Increased respiratory rate Gastrointestinal and urinary systems are affected Laboratory values impact

Maternal and Fetal Adaptation to Labor (cont.) Maternal psychological adaptation Early stage of labor – excited and talkative Active labor More introverted Focusing energies on coping with stress of contractions Transition: Feels out of control Pushing phase: Feels more in control

Maternal and Fetal Adaptation to Labor (cont.) Increase in intracranial pressure Placental blood flow temporarily interrupted at peak of uterine contractions Stresses cardiovascular system; results in slowly decreasing pH throughout labor Passing through the birth canal is beneficial in two ways Stimulates surfactant production; helps clear respiratory passageways

Maternal and Fetal Adaptation to Labor (cont.) Ecchymosis Edema Caput succedaneum Cephalohematoma