Second stage of labor

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 Second stage of labor 



Definition :
"second stage of labor starts from the full dilatation of cervix (not from the rupture of the membranes ) and ends with expulsion of the fetus from the birth canal ."

This stage is concerned with the descent and delivery of the fetus through the birth canal.

Second stage of labor has two phases :
  1. Propulsive : From full dilatation until head touches the pelvic floor .
  2. Expulsive: since the time mother has irritable desire to 'bear down' and push until the baby is delivered .
Delivery of the fetus is accomplished by the downward thrust offered by uterine contraction supplemented by voluntary contraction of abdominal muscle against the resistance offered by bony and soft tissue of the birth canal .
There is always a tendency to push the fetus back into the uterine cavity by the elastic recoil of the tissue of the vagina and the pelvic floor.
This is effectively counterbalance by power of retraction.
power of retraction , the fetus is gradually expelled from the uterus against the resistance offered by the pelvic floor.
After the expulsion of fetus , the uterine cavity is permanently reduces in size only to accommodate the after births.
The expulsive force of uterine contraction is added by voluntary contraction of the abdominal muscles called "Bearing down efforts "  

CLINICAL COURSE OF SECOND STAGE OF LABOR :
  1. PAIN 
  2. Bearing down efforts 
  3. Membranes status 
  4. Descent of the fetus
  5. Vaginal signs 
  6. Maternal sign
  7. Fetal effects
  • PAIN : The intensity of the pain increases. The pain comes at intervals of 2-3 minutes and lasts for about 1-2 min . It become successive with increasing intensity in the second stage. It becomes successive with increasing intensity in the second stage .
  • BEARING DOWN EFFORTS : It is the additional voluntary expulsive efforts that appears during the second stage of labor. It is initiated by nerve reflex set up due to stretching of the vagina by the presenting part .Sustained pushing beyond the uterine contraction is discourage . Premature bearing down efforts may suggest uterine disfunction . There may be slowing of the FHR during pushing and it should come back to normal once the contraction is over.
  • MEMBRANES STATUS : Membrane may rupture with a gush of liquor per vagina. Rupture may occasionally be delayed till the head bulges out through the introitus . 
  • DESCENT OF THE FETUS : Features of descent of the fetus are evident from abdominal and vaginal examination . Internal examination reveals descent of the head in relation to ischial spine and gradual rotation of the head evidenced by position of the sagittal suture, and the occiput in relation to the quadrants of the pelvic.
Advantages over "station of head " in relation to the ischial spine :
  1. It include the variability due to caput and molding or by a different depth of the pelvis.
  2. The assessment is quantitative and can be easily reproduce .
  3. Repeated vaginal examination are avoided.
  • VAGINAL SIGN : As the head descent down ,it distends the perinium , the vulval opening looks like a slit through which the scalp hair is visible . During each contraction , the perinium is markedly distended with the overlying skin tense and glistening and the vulval opening become circular
  • MATERNAL SIGN : There are features of exhaustion. Respiration is , however , slowed down with increased perspiration . During the bearing down efforts , he face becomes congested with neck vein prominent . Immediately following the expulsion of the fetus , the mother heaves the sign of relief
  • FETAL EFFECT : Slowing of FHR during contractions is observed, which comes back to normal before the next contraction.

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