Normal Labor and Its Types

Normal Labor

• Theories on the onset of labor are not required for the exam.
• Estrogen stimulates uterine muscle softening, stretching, and thinning.
• Progesterone relaxes uterine smooth muscle, preventing contractions.
• Oxytocin and prostaglandins have a role in labor.
• Fetal cortisol increases near term.
• Uterine distention triggers labor.

Types of Labor

• False labor (Braxton Hicks): Irregular contractions, no cervical changes, intensity does not increase.
• True labor: Progressive contractions, cervical changes (effacement and dilation), back pain radiating to the front, rupture of membranes (ROM). Contractions are not easily stopped and occur on a regular interval. Presenting part descends.
• Bloody show usually precedes true labor.

Critical Factors in Labor (Four P's)

• Passage: Pelvic dimensions impact labor. Gynecoid pelvis is the most favorable for vaginal delivery.
• Passenger: Fetal presentation (vertex = head first, breech = buttock/feet first, shoulder), attitude, lie, and station.
• Powers: Uterine contractions (frequency, duration, intensity) and maternal pushing efforts
• Psyche: Psychological state of the laboring woman influences labor.

Fetal Presentation

• Determined by the body part of the fetus that enters the pelvis first.
  • Cephalic (head first) is the most common. Different types of cephalic presentations include (vertex, brow, face)

Fetal Lie & Attitude

• Lie: Relationship of the spine of the fetus to the maternal spine
  • Longitudinal: fetal spine parallel to maternal spine (most favorable)
  • Transverse: fetal spine at right angle to maternal spine (not favorable).
• Attitude: Relationship of fetal body parts to each other (Flexion).
  • Flexion: General flexion (optimum), and deviations from flexion can create a harder labor.

Fetal Station

• Relationship of the presenting part to maternal ischial spines.
• Negative station means the presenting part is above the ischial spines.
• Positive station means the presenting part is below the ischial spines.

Fetal Position

• Relationship of the presenting part to the maternal pelvis's four quadrants.

Fetal Monitoring:

• External monitoring uses a tocodynamometer and ultrasound to measure frequency, duration, and intensity of contractions.
• Internal monitoring uses an intrauterine pressure catheter (IUPC) to measure intrauterine pressure to measure intensity, and a fetal scalp electrode to measure FHR (more accurate).

Premonitory Signs/Symptoms

• Lightening - fetus descending into pelvis
• Braxton Hicks contractions
• Cervical changes (softening)
• Bloody show

Stages of Labor

• First stage: Onset of true labor to complete cervical dilation (10 cm)
  • Latent phase: early dilation (0-3 cm), contractions mild
  • Active phase: dilation continues, contractions increase in frequency, duration, and intensity(4-7 cm)
  • Transitional phase: dilation is near completion (8-10 cm), contractions intense.
• Second stage: Complete dilation to delivery of the baby
• Third stage: Delivery of the placenta to separation of the placenta
• Fourth stage: 1-4 hours after delivery, focusing on maternal recovery

Complications

• Preterm Labor: Onset of labor between 20 and 37 completed weeks of pregnancy.
• Premature Rupture of Membranes (PROM): Rupture of membranes prior to the onset of labor.
• Placenta Previa: Placental implantation in the lower uterine segment, potentially covering the cervix.
• Abruptio Placenta: Premature separation of the placenta from the uterine wall.
• Incompetent Cervix: Premature dilation of the cervix, requiring a cerclage (stitch).
• Gestational diabetes: Carbohydrate/glucose intolerance, often requiring increased glucose monitoring and control.