Podcast
Questions and Answers
What is the primary factor that triggers the onset of labor?
What is the primary factor that triggers the onset of labor?
Maturity of the fetus and mechanical considerations for birth
Which of the following theories explain the onset of labor? (Select all that apply)
Which of the following theories explain the onset of labor? (Select all that apply)
What are preliminary signs of labor?
What are preliminary signs of labor?
Lightening, increase in activity, slight loss of weight, Braxton Hicks contractions, and ripening of the cervix
What is the surest sign that labor has begun?
What is the surest sign that labor has begun?
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True or False: The mucus plug is expelled during the early stages of labor.
True or False: The mucus plug is expelled during the early stages of labor.
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What changes in the cervix occur as labor approaches?
What changes in the cervix occur as labor approaches?
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Labor may begin with rupture of the membranes, experienced as a _____ or slow seeping of clear fluid.
Labor may begin with rupture of the membranes, experienced as a _____ or slow seeping of clear fluid.
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Study Notes
Theories of Labor Onset
- Labor typically starts when a fetus is mature enough for extrauterine life but not too large to cause birth complications.
- Several theories explain why labor begins, including combined factors from both mother and fetus:
- Uterine muscle stretching: Triggers release of prostaglandins.
- Pressure on the cervix: Stimulates oxytocin release from the posterior pituitary.
- Oxytocin stimulation: Works with prostaglandins to initiate contractions.
- Change in estrogen to progesterone ratio: Increasing estrogen relative to progesterone (interpreted as progesterone withdrawal).
- Placental age: Triggers contractions at a specific point.
- Rising fetal cortisol levels: Reduces progesterone formation and increases prostaglandin formation.
- Fetal membrane production of prostaglandin: Stimulates contractions.
Signs of Labor
Preliminary Signs of Labor
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Lightening: Descent of the fetal presenting part into the pelvis.
- Occurs about 10-14 days before labor in first-time mothers.
- Changes abdominal contour, lowers uterus position.
- Relaxes diaphragm pressure and shortness of breath.
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Increase in Activity: Related to an increase in epinephrine due to decreased placental progesterone.
- Prepares the body for the work of labor.
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Slight Loss of Weight: Progesterone decrease allows for easier fluid excretion.
- Increased urine production can lead to a 1-3 pound weight loss.
- Braxton Hicks Contractions: Become stronger and more noticeable.
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Cervical Ripening: Cervix softens, becomes "butter-soft" and tips forward.
- Indicates labor is imminent.
Signs of True Labor
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Uterine Contractions: Involuntary and unpredictable, increasing in intensity.
- Regular, consistent contractions that become stronger, longer, and closer together.
- Show: Pinkish mucous discharge from the vagina as the cervical capillaries bleed due to fetal pressure.
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Rupture of Membranes: Release of amniotic fluid, either as a sudden gush or a slow leak.
- Can cause fetal head to settle in the pelvis, shortening labor.
- Risks include intrauterine infection and umbilical cord prolapse, which can cut off oxygen supply to the fetus.
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Description
This quiz explores key theories behind the onset of labor and the preliminary signs that indicate its commencement. Understand the physiological changes in both the mother and fetus that lead to labor initiation. Test your knowledge on critical concepts like uterine muscle stretching, hormone influences, and fetal factors.
