Chapter 8 The Labor Process Copyright 2014 Wolters

Four Essential Components of Labor • The Four Ps of Labor – Passageway – Passenger – Powers – Psyche • Problematic areas influence labor negatively Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Passageway (cont. ) – Pelvic shape • Gynecoid ‒ Most favorable for a vaginal birth ‒ Rounded shape • Anthropoid ‒ Elongated shape • Android ‒ Heart-shaped Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Passageway (cont. ) – Pelvic shape (cont. ) • Platypelloid ‒ Flat in its dimensions – Pelvic dimensions • Most important is obstetric conjugate – Soft tissues • Cervix • Vagina Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Question State whether the following statement is true or false. The gynecoid pelvis is

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

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Passenger (cont. ) ‒ Fetal lie (cont. ) • Transverse lie ‒ 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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) Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Answer b. Flexion Rationale: The most common, most favorable attitude for a vaginal birth, is an attitude of flexion, also called a vertex presentation. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Process of Labor • Onset of labor – Theories regarding labor onset • Progesterone withdrawal theory • Oxytocin theory • Prostaglandin theory – Maternal and fetal factors • Cascade effect Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Mechanisms of a Spontaneous Vaginal Delivery • Cardinal movements (mechanisms of delivery) – Engagement – Descent – Flexion – Internal rotation – Extension – External rotation – Expulsion Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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

Answer b. Second stage Rationale: The second stage begins when the cervix is dilated

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Maternal and Fetal Adaptation to Labor (cont. ) • Fetal adaptation to labor – Increase in intracranial pressure – Placental blood flow temporarily interrupted at peak of uterine contractions • Stresses cardiovascular system; results in slowly decreasing p. H throughout labor – Passing through the birth canal is beneficial in two ways • Stimulates surfactant production; helps clear respiratory passageways Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Maternal and Fetal Adaptation to Labor (cont. ) • Fetal adaptation to labor (cont. ) – Ecchymosis – Edema – Caput succedaneum – Cephalohematoma Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins