Parturition - Stages of labor Flashcards Preview

OBGYN - 3. OB normal > Parturition - Stages of labor > Flashcards

Flashcards in Parturition - Stages of labor Deck (17):

Stages, end and beginning

  • First stage
    • Starts with painful regular contractions (5 minutes apart for 1 hour, i.e. ≥ 12 contractions per hour)
    • Ends with cervical dilatation
  • Second stage
    • Starts with 10 cm cervical dilatation
    • Ends with fetal delivery
  • Third stage
    • Delivery of placenta and membranes


Labor initiation is heralded by ____

Bloody show


Contractions are painful possible because of:

  1. Hypoxia to myometrium
  2. Compression of the nerve ganglia
  3. Cervical stretching during dilatation
  4. Stretching of peritoneum overlying fundus


What is the Ferguson reflex?

Mechanical stretching of the cervix enhances uterine activity


T/F. The myometrium relaxes to its original length after contraction



Explain the formation of physiologic retraction ring

  • The upper uterine segment becomes progressively thickened throughout thr 1st and 2nd stage of labor
  • The lower segment is thinning
    • Concommitant occurence causes physiologic retraction ring formation


Explanation for the formation of pathological retraction ring (of Bandl)

Happens when the thinning of the lower uterine segment is extreme as in obstructed labor, the ring is prominent leading to formation of pathologic retraction ring


Most important force in fetal expulsion

Pushing or maternal intraabdominal pressure


Forces that cause cervical dilatation

  • Centrifugal pull exerted on the cervix
  • Hydrostatic action of the amniotic sac or presenting part (if membranes are present) dilates the cervical canal like a wedge


The leading portion of fluid and amniotic sac located in front of the presenting part that is formed during the process of cervical effacement and dilatation



The pattern of cervical dilatation during preparatory and dilatational divisions of normal labor


A image thumb

Description of uterine contractions during the 2nd stage of labor

UC averages from 30-90 seconds, averaging around 1 minute, interval between contractions is around 1 minute or less


____ curve is formed when the station of the fetal head is plotted as a function of labor duration


A image thumb

Fetal and maternal structures used as references in measuring station

Fetal biparietal diameter in relation to a line drawn between maternal ischial spines

A image thumb

Phase in the Friedman curve where increased rates of descent are observed in nulliparas

Phase of maximum slope


Signs of placental separation (in order)

  1. Uterus becomes globilar and firmer (Calkin's sign)
  2. Sudden gush of blood
  3. Uterus rises in the abdomen
  4. Lengthening of the cord


How does blood 'escape' in Schultze vs Duncan mechanism?

  • Schultze
    • blood from the placental site pours into the membrane sac and does not escape externally until after extrusion of the placenta
  • Duncan
    • placenta separates first at the periphery and the blood collects between the membranes and the uterine wall and escapes from the vagina
    • Placenta descends sideways, maternal surface appears first

A image thumb