2. Labour definition
◦ WHO defines normal labour as “spontaneous in onset,low-
risk at the start of labour and remaining so throughout labor
and delivery.The infant is born spontaneously in the vertex
position between 37 and 42 completed weeks of
pregnancy.After birth,mother and infant are in good
condition “
◦ Mechanism of normal labour is the manner in which the fetus
adjusts itself to pass through the partiurient canal with
minimal difficulty
3. ◦ Delivery of head in left occipitoanterior position is seen in majority of
women
◦ ABDOMINAL PALPATION
◦ In LOA the lie is longitudinal, attitude is flexion and presenting part is
vertex.On abdominal palpation, the back will be on the left side and the
limbs on the right side. The vertex will usually be well flexed and fixed.
◦ Fetal heart sounds will be heard clearly in the left lower quadrant of the
maternal abdomen.
◦ VAGINAL EXAMINATION
◦ In LOA, the occipital and hence the posterior fontanelle is in the left
anterior quadrant.
◦ As head is flexed posterior fontanelle will be easily felt but not the
anterior.
6. ENGAGEMENT
◦ Engagement is said to occur when the greatest transverse diameter of
the presenting part, has passed through the pelvic inlet.
◦ In cephalic presentations the greatest transverse diameter is always the
biparietal.
◦ The engaging diameter is the anteroposterior diameter of head. The
diameter of engagement is the diameter of pelvic inlet in which head
engages-transverse or oblique.
◦ Once engagement occurs on abdominal palpation either no part or
only one fifth of the head will be palpable.
7.
8.
9.
10. Synclitism and Asynclitism
◦ Synclitic engagement is said to occur
when the sagittal suture lies in the
transverse diameter of the pelvic inlet
midway btw pubic symphysis and sacral
promontory.
◦ Usually sagittal suture is deflected
anteriorly or posteriorly in which case
there is said to be asynclitism.
11.
12.
13. DESCENT
◦ Continous movement brought about by four factors.
◦ 1. Direct pressure of fundus on the breech during contraction
◦ 2. Hydrostatic pressure of amniotic fluid
◦ 3. Extension and straightening of fetal body
◦ 4. Abdominal muscle contractions
14. FLEXION
◦ As head meets resistance from
pelvic floor or cervix ,flexion occurs
and brings head into contact with
the chest and the presenting
diameter becomes the sub
occipitobregmatic which is the
shortest anteroposterior diameter.
15.
16. INTERNAL ROTATION
◦ Inlet of pelvis- Transverse oval
◦ Outlet of pelvis- Anteroposterior oval
◦ Thus minimum diameter of fetal head has to enter inlet in transverse
diameter and rotate internally into anteroposterior diameter for head to
pass through the outlet
◦ When occiput touches the pelvic floor there is elastic recoil of levator
ani muscles.
◦ This causes head to rotate 45° to the midline hence bringing the
occiput to lie near pubic symphysis.
17.
18.
19.
20.
21. EXTENSION
◦ Result of 2 forces ie the uterine contractions exerting downward
pressure from above and pelvic floor offering resistance from below.
◦ Crowning occurs then by process of extension the occiput,
vertex,bregma, forehead, nose, mouth and finally the chin are born in
sequence.
22.
23. EXTERNAL ROTATION
◦ RESTITUTION: Head rotates posteriorly by 45°(1/8)
◦ EXTERNAL ROTATION: Again head rotates posteriorly by 45°(1/8)
◦ total posterior head rotation 2/8 th ie 90°
◦ SHOULDERS rotate posteriorly by 1/8th manifested as external
rotation of head by 45°.
