normal labor

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Normal Labor


Definition

• The series of the events that takes place from the uterine contraction to the expulsion of placenta normally.


Stages of Labor

• Four stages1. First stage of labor

a. Latent Phaseb. Active Phase

2. Second stage of Labor3. Third stage of Labor4. Fourth stage of Labor


First Stage of Labor

• Begins with onset of regular uterine contraction

• Ends with complete cervical dilation at 10 cm


Latent Phase• Contractions become progressively stronger

longer and more frequent and better coordinated

• Cervix effaces but shows minimal dilation• Duration:(May be intermittent over several days or may last only few hours)– Nulliparas: Average 8 hours– Multiparas: Average 5 hours


Active Phase

• Cervix dilates usually from 3-4 cm to full dilation i.e. 10 cm

• Duration more predictable• Duration and Rates – Nullipara: 5 hours; 1.2 cm/hour– Multipara: 2 hours; 1.5 cm/hour


Second Phase

• Begins with complete cervical dilation

• Ends with delivery of the baby


Third Stage• Begins with the delivery of

baby• Ends with delivery of placenta• Placenta separation from

uterine wall occurs as the result of myometrium contraction shear off anchoring villi

• Duration:– <30 minutes in all women


Fourth Stage

• First one hour after delivery• Vital signs and any evidence of uterine atony

or postpartum hemorrhage• Perineum inspection for any signs of

hematoma formation• Mother should be seen every 15 mins• Newborn undergoes initial assessment


Cardinal Movement of Labor1. Engagement2. Descent3. Flexion4. Internal Rotation5. Extension6. External Rotation7. Expulsion


Engagement• Movement of the

presenting part below the plane of the pelvic inlet

• Engaging process start at the last few weeks of pregnancy to the period of starting of labor


Descent• Movement of presenting

part down through the curve of the birth canal

• Result of :– Pressure of amniotic fluid– Direct pressure of the fundus

upon the breech with contraction

– Bearing down effect of maternal abdominal muscle

– Extension and straightening of fetal body


Flexion

• Placement of fetal chin on the thorax

• Result from resistant of cervix , wall of pelvis or pelvic floor


Internal Rotation• Rotation of the position

of the fetal head in the mid pelvis from transverse to anterior-posterior

• Essential for the completion of labor


Extension• Movement of fetal chin

away from the thorax as it reaches to vulva

• Forces acting:– First force-exerted by uterus -

acts posteriorly– Second force by resistant pelvic

floor and symphysis- acts anteriorly

(Resultant vector is in the direction of vulvar opening, causing extension)


External Rotation(Restitution)

• Rotation of the fetal head outside the mother as the head passes through the pelvic outlet

• One shoulder is anterior behind the symphysis and other is posterior due to external rotation


Expulsion• Delivery of fetal

shoulders and body


Fetal Skull

Figure. Fetal skull from lateral view


Figure. Fetal skull superior view


Diameter of fetal skull(Lateral view)


Diameter of fetal skull(Superior view)


Abnormal fetal head presentation

• Face Presentation• Brow Presentation


Face presentation• The head is hyperextended so that the occiput is in

contact with the fetal back, and the chin is present• Causes include– Preterm infant with smaller head dimension– Enlargement of neck due to coiling of the cord – Anencephalic fetus naturally present with this

• Diagnosis– The radiographic demonstration of the hyper extended head

with facial bone at or below the pelvic inlet(characterstic)


Brow Presentation• Diagnosed when the portion of the fetal head

between the orbital ridge and anterior fontanel presents at pelvic inlet

• Causes:• Same as face presentation

• Usually on vaginal examination the frontal suture, large anterior fontanel orbital ridges and root of the nose are felt but never mouth and chin is palpable


Abnormal labour

• Shoulder dystociaMeans difficult labor: slow labor progress Causes1.Uterine contraction problem2.Abnormal presentation, position3.Contracted bony pelvis4.Soft tissue obstructioni.e. power, passenger and passage’s problem

Asynclitism: malposition of head within pelvis – causes CPDFailure to progress: means defect in cervical dilatation or descent


Prolonged latent phase: N:>20hr M:>14hr Protracted disorder: active phase: N: <1.2cm/hr M:<1.5cm/hr for more than 4

hr Descent: N: <1cm/hr M:<2cm/hr Arrest disorder: failure of descent, no dilation for 2hr To call protracted or arrest, cervical dilatation should be >3 or 4cm

Fundus and cervix has different intensity and time differential in onset of contraction.Uterine dysfunction: 1. hypotonic: synchronous but less powerful contraction2. Hypertonic or incoordinated: gradient distortion presentCause: chorioamnionitis, epidural analgesia, back lying of mother, First stage disorder: uterine dysfunction mainly2nd stage disorder: obvious for passage and passenger disproportion

High station is also a risk factor for dystocia


Precipitous labor: expulsion of fetus in <3hr (cervical dilatation: N: >5cm/hr M:>10cm/hr

No complication occur when cervix dilated, vagina stretched and perineum relaxed. If not then uterine rupture or severe injury to birth canal can occur. Amnionic fluid embolism can also occur.

much Chance of uterine atony- PPH Fetal effect: hematoma, anoxia due to contracted uterus, erb palsy or

Duchenne brachial palsy Ttmnt: tocolytics such as Mag salt

Fetopelvic disproportion: due to contracted pelvis: if shortest AP distance <10cm and transverse <12cm


References

• Kevin p. Henretty. Obstratics Anatomy. Obstetrics illustrated. Churchill Livingstone. Elsiver. Page no. 54-5.

• Oxford Handbook of Clinical Specialties, 5th edn (ed. Collier J, Longmore M, Brown TD), p. 87.

• Rouse, Hauth, et.al. William Obstetrics. 23rd Edition. Normal Labour.


Thank You!

normal labor

Health & Medicine

stage of labor

hours multiparas

hours nulliparas

minimal dilation duration

complete cervical dilation

delivery of baby ends

predictable duration

uterine wall