Physiology of Normal Labor
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Questions and Answers

What gestational age is considered to define premature labor?

  • 38-40 weeks
  • 28-37 weeks (correct)
  • 41 weeks or more
  • 20-27 weeks

Which theory suggests that a decrease in progesterone and an increase in estrogen lead to the onset of labor?

  • Oxytocin stimulation theory
  • Uterine distention theory
  • Progesterone withdrawal theory (correct)
  • Prostaglandin production theory

What hormone's increase is associated with stimulating uterine contractions during labor?

  • Prolactin
  • Oxytocin (correct)
  • Estrogen
  • Luteinizing hormone

Which theory posits that an increase in intra-abdominal pressure initiates labor?

<p>Mechanical uterine distention theory (D)</p> Signup and view all the answers

What physiological substance promotes cervical ripening in preparation for labor?

<p>Prostaglandins (D)</p> Signup and view all the answers

Which factor is NOT part of the 5Ps affecting labor progression?

<p>Pain management (C)</p> Signup and view all the answers

The gradual increase of which hormone during pregnancy peaks in the second stage of labor?

<p>Oxytocin (B)</p> Signup and view all the answers

Which factor does NOT directly affect the mother's ability to progress in labor?

<p>Gestational age of the fetus (B)</p> Signup and view all the answers

Which part of the fetal head is known for overlapping at the suture line to facilitate delivery?

<p>Molding (B)</p> Signup and view all the answers

What is the significance of the anterior fontanelle in the fetal skull?

<p>It is diamond-shaped and located at the junction of the sagittal, coronal, and frontal sutures. (C)</p> Signup and view all the answers

Which factor does NOT affect the progress of labor?

<p>Maternal age (C)</p> Signup and view all the answers

In which type of delivery does engagement occur during labor?

<p>Only in multipara (B)</p> Signup and view all the answers

What term describes the relationship of body parts of the fetus?

<p>Fetal lie (A)</p> Signup and view all the answers

What does fetal engagement refer to?

<p>The settling of the presenting part in the pelvis (D)</p> Signup and view all the answers

Which statement about fetal sutures is incorrect?

<p>There are six main sutures in the fetal head. (D)</p> Signup and view all the answers

Which structure facilitates the assessment of fetal engagement during examination?

<p>Ischial spines (D)</p> Signup and view all the answers

What is the site of pain during true labor pains?

<p>Lower back and abdomen (B)</p> Signup and view all the answers

Which phase of uterine contraction is characterized by maximal pressure?

<p>Acme (D)</p> Signup and view all the answers

What happens to cervical dilatation during true labor?

<p>It is progressive. (C)</p> Signup and view all the answers

What term describes the time between the start of one contraction to the start of the next?

<p>Frequency (D)</p> Signup and view all the answers

Which of the following is a characteristic of false labor pains?

<p>Relieved by sedatives (A)</p> Signup and view all the answers

During which phase of uterine contraction does intra-uterine pressure start to increase?

<p>Increment (D)</p> Signup and view all the answers

What is the primary role of uterine contractions during labor?

<p>To efface and dilate the cervix (A)</p> Signup and view all the answers

What is the range of pressure (in mmHg) at which pain is typically felt during uterine contractions?

<p>20-25 mmHg (A)</p> Signup and view all the answers

What is the definition of normal labor?

<p>A spontaneous delivery of a full-term, viable fetus without complications. (B)</p> Signup and view all the answers

What characterizes prolonged labor?

<p>Labor that lasts more than 24 hours. (D)</p> Signup and view all the answers

What is one of the factors that affects labor as mentioned in the content?

<p>Maternal age and health. (D)</p> Signup and view all the answers

Which theory relates to the onset of labor?

<p>Hormonal changes theory. (C)</p> Signup and view all the answers

Which of the following signifies true labor?

<p>Regular uterine contractions leading to cervical changes. (B)</p> Signup and view all the answers

What is the duration of labor for a primigravida?

<p>12 to 18 hours. (A)</p> Signup and view all the answers

What distinguishes precipitate labor from normal labor?

<p>It lasts less than 3 hours. (B)</p> Signup and view all the answers

Which stage of labor involves signs of the placental separation?

<p>Third stage of labor. (D)</p> Signup and view all the answers

What is the duration of the latent phase of the first stage for a primipara?

<p>10-15 hours (B)</p> Signup and view all the answers

How much cervical dilation is expected during the transitional phase?

<p>8-10 cm (A)</p> Signup and view all the answers

What is the frequency of uterine contractions during the active phase?

<p>3/10 to 4/10 (D)</p> Signup and view all the answers

What maternal behavior is typically observed during the active phase?

<p>Uncooperative (B)</p> Signup and view all the answers

How often do uterine contractions occur in the second stage of labor?

<p>Every 2 to 3 minutes (A)</p> Signup and view all the answers

What is the expected duration of contractions in the second stage of labor?

<p>60 to 90 seconds (D)</p> Signup and view all the answers

What is a sign that the bag of water should have ruptured by the end of the first stage?

<p>Dilated cervix (D)</p> Signup and view all the answers

Which type of maternal behavior indicates the transitional phase of labor?

<p>Fatigued and irritable (C)</p> Signup and view all the answers

What occurs during the extension of the fetal head as it reaches the perineum for birth?

<p>The occiput emerges first, followed by the face and chin. (A)</p> Signup and view all the answers

What is the purpose of external rotation of the fetal head after birth?

<p>To allow the shoulders to rotate internally and fit the maternal pelvis. (C)</p> Signup and view all the answers

Which sequence describes the order of emergence of the fetal head during birth?

<p>Occiput, face, chin. (D)</p> Signup and view all the answers

What does internal rotation of the fetal head accomplish?

<p>Aligns the head with the anteroposterior diameter of the pelvic outlet. (D)</p> Signup and view all the answers

During which phase does the expulsion of the fetal body primarily occur?

<p>Immediately following external rotation of the head. (B)</p> Signup and view all the answers

What initiates the external rotation of the fetal head post-delivery?

<p>The position of the fetal shoulders. (B)</p> Signup and view all the answers

What is the anteroposterior diameter in relation to fetal delivery?

<p>The widest portion of the maternal pelvis. (A)</p> Signup and view all the answers

What marks the beginning of the third stage of labor?

<p>Delivery of the fetus. (D)</p> Signup and view all the answers

Flashcards

Normal Labor

A complete and spontaneous process of delivering a full-term, single, viable fetus through the natural birth canal, without assistance, and without complications within 24 hours of the onset of true labor pains.

Prolonged Labor

A labor lasting more than 24 hours.

Precipitate Labor

A labor lasting less than 3 hours.

Viability

A reasonable chance of the fetus surviving outside the uterus, typically after 28 weeks of pregnancy.

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Labor duration (primigravida)

Typically lasts 12-18 hours for first-time mothers.

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Labor duration (multigravida)

Usually shorter, lasting about 6-10 hours for subsequent pregnancies.

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Labor

Regular uterine contractions that result in cervical effacement and dilation leading to delivery of a viable fetus and placenta.

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Normal labor conditions

Full-term, single, viable fetus, vertex presentation without assistance and without complications.

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Premature labor

Labor that occurs between 28 and 37 weeks of gestation, resulting in a premature fetus.

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Progesterone withdrawal theory

Progesterone normally slows uterine contractions. As progesterone levels decrease, causing increased estrogen and oxytocin receptor sensitivity, leading to uterine contractions; triggering labor.

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Prostaglandins

Hormones that stimulate uterine contractions and cervical ripening, preparing for childbirth.

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Uterine distention theory

The growing fetus puts pressure on the uterus. This pressure, increases intra-abdominal pressure, triggering the onset of labor.

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Placental ischemia

Reduced blood flow to the placenta causing its degeneration and the release of oxytocin-inducing agents causing or promoting labor

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Oxytocin

A hormone that stimulates uterine contractions and increases during labor, especially in the second stage.

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Passenger in labor

The baby's size, position, and attitude during childbirth.

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Labor factors (5Ps)

Key elements affecting labor's progress: Passenger (baby), Passage (birth canal), Power (contractions), Position (mother), and Psyche (mother's mental state).

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Fetal Head Sutures

Fibrous bands connecting fetal skull bones.

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Fetal Head Molding

Overlapping of fetal skull bones to ease birth.

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Fetal Engagement

Fetal presenting part reaching pelvic ischial spines.

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Fetal Fontanelle

Junction points of fetal skull sutures, soft spots.

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Anterior Fontanelle

Diamond-shaped soft spot on top of head.

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Posterior Fontanelle

Triangular soft spot on back of head.

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Fetal Station

Fetal position relative to maternal ischial spines.

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Fetal Presentation

First body part of the baby entering the pelvis.

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True Labor Pains

Regular contractions in the abdomen and lower back, increasing in frequency, strength, and duration, with progressive cervical dilation and bulging membranes.

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False Labor Pains (Braxton Hicks)

Irregular contractions in the abdomen, without progressive cervical change, often relieved by rest or sedation.

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Uterine Contraction Phases

Uterine contractions are in three phases: Increment (pressure builds), Acme (peak pressure), Decrement (pressure fades).

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Uterine Contraction Frequency

The time between the start of one contraction and the start of the next.

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Uterine Contraction Duration

The time from the beginning of the contraction's increase (increment) to the end of its decrease (decrement).

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Uterine Contraction Intensity

The strength of the uterine contraction at its peak (acme).

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Labor's Role of Membranes

Membrane integrity optimizes fetal oxygen supply and prevents intrauterine infection.

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Uterine Contraction Functions

Uterine contractions cause cervical effacement and dilation, fetal engagement and rotation, placental separation, and uterine tone return.

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Internal Rotation (Head)

The fetal head rotates so that its longest diameter aligns with the widest part of the pelvis, enabling it to pass effectively through the birth canal.

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Extension (Head)

As the head descends, the occiput emerges first, followed by the face and chin, as the head extends under the pubic bone.

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Restitution (Head)

After birth, the head briefly rotates back to its original position at engagement, allowing the shoulders to align for delivery.

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Internal Rotation (Shoulders)

Similar to the head, the shoulders rotate to align with the widest diameter of the pelvis, allowing the anterior shoulder to emerge first.

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External Rotation (Head)

After the shoulders are born, the head rotates to its final position, aligning with the baby's body.

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Expulsion (Body)

The anterior shoulder emerges first under the pubic bone, followed by the posterior shoulder. The rest of the body is then delivered.

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Third Stage of Labor

This stage begins with the delivery of the baby and ends with the delivery of the placenta.

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Placental Stage

The third stage of labor, specifically focusing on the detachment and delivery of the placenta.

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Cervical Dilation

The opening of the cervix, measured in centimeters, during labor. It progresses from 0 cm (fully closed) to 10 cm (fully dilated) to allow the baby to pass through.

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Cervical Effacement

The thinning of the cervix, measured as a percentage, during labor. It progresses from 0% (thick) to 100% (completely thinned) to allow the baby to move down the birth canal.

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Phases of the First Stage of Labor

The first stage of labor divided into three phases: Latent, Active, and Transitional.

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Involuntary Bearing Down

The natural urge to push during labor, as the baby descends into the birth canal. Usually occurs in the transition phase of the first stage.

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Rupture of the Membranes

The breaking of the amniotic sac, releasing amniotic fluid. It can occur naturally or be broken by a healthcare provider.

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Study Notes

Physiology of Normal Labor

  • Labor: The process of regular uterine contractions, cervical effacement and dilation, resulting in the delivery of a viable fetus and placenta.
  • Viability: A reasonable chance of the fetus to live outside the uterus, usually at 28 weeks of pregnancy.
  • Normal Labor: A complete and spontaneous delivery of a full-term, single, viable fetus through the natural birth canal within 24 hours of true labor pain onset, without assistance or complications for the mother or newborn.
  • Duration of Normal Labor:
    • Primigravida (first pregnancy): Typically 12-18 hours.
    • Multigravida (subsequent pregnancies): Usually shorter, around 6-10 hours.
  • Prolonged Labor: Labor lasting more than 24 hours.
  • Precipitate Labor: Labor lasting less than 3 hours.
  • Premature Labor: Results in a premature fetus, occurring between 28-37 weeks of gestation.

Content Outline

  • Definition of terms (labor, viability, normal labor, etc.)
  • Theories of labor onset (progesterone withdrawal, prostaglandin production, uterine distention, placental ischemia, oxytocin stimulation)
  • Factors affecting labor (5Ps: Passenger, Passage, Power, Position, Psyche)
  • Prodromal stage (premonitory signs of labor)
  • Signs of true labor (differentiation from false labor pains)
  • Nature of uterine contraction (phases: increment, acme, decrement)
  • Stages of labor (first stage, second stage, third stage, fourth stage)
  • Phases of the First Stage (latent, active, transitional)
  • Signs of the Second Stage of Labor
  • Mechanism of labor (descent, flexion, internal rotation, extension, external rotation, expulsion)
  • Signs of Placental Separation
  • Mechanisms of placental separation (Schultze's and Duncan's mechanisms)
  • Fourth stage of labor (restorative stage)

Factors Affecting Labor (5Ps)

  • Passenger: Fetus, placenta, membranes, umbilical cord, blood, amniotic fluid, fetal head (size, molding, attitude, lie, presentation, position, station, engagement)
  • Passage: Birth canal (bony pelvis)
  • Power: Uterine contractions (frequency, duration, intensity)
  • Position: Maternal position during labor.
  • Psyche: Maternal psychological response (emotional state, anxiety, stress, fear, pain tolerance)

Signs of Normal Labor

  • Premonitory Signs:
    • Lightening (uterine descent)
    • Frequency of urination
    • Cervical effacement (shortening and thinning of the cervix)
    • Cervical ripening and softening.
    • Braxton Hicks contractions
    • Bloody show
    • Rupture of membranes (water breaking)
  • True Labor Signs:
    • Progressive cervical dilation
    • Regular uterine contractions with increasing frequency, duration, and intensity
    • Discomfort that includes lower back pain; abdominal pain, or pain in the abdomen and lower back.

Mechanism of Labor

  • Descent: The progress of the presenting part through the pelvis (measured by the station).
  • Flexion: The chin of the fetal head flexes toward the chest to encounter resistance.
  • Internal Rotation: The fetal head rotates as it descends and engages.
  • Extension: The head extends as it passes through the pelvic outlet.
  • External Rotation (Restitution): The head rotates to its original position, allowing the shoulders to rotate.
  • Expulsion: The complete birth of the baby.

Placental Separation

  • Two mechanisms: Schultze's method and Duncan's method.

Stages of Labor

  • First Stage: Cervical dilatation and effacement (latent phase, active phase, transitional phase).
  • Second Stage: Expulsion of the fetus.
  • Third Stage: Delivery of the placenta.
  • Fourth Stage: Recovery (1-2 hours)

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Description

Explore the essential concepts related to the physiology of normal labor, including definitions of labor, viability, and normal labor. Learn about the durations of labor for primigravida and multigravida pregnancies and the distinctions among prolonged, precipitate, and premature labor.

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