There is an interplay of physiological processes occurring during the second stage of labour. Second stage is said to have two phases, latent and active. It is during the latent phase that the presenting part passes through the fully dilated cervix to the birth canal.

1. PHYSIOLOGICAL CHANGES IN SECOND STAGE OF LABOR
MUKESH SAH, MD
PGI
GOODSAM MEDICAL CENTER

2. second stage of labor
• It start from the full dilatation of the cervix and the ends with
expulsion of the fetus from the birth canal.
• It has got two phases:
a. Propulsive phases- starts from full dilatation up to the descent
of the presenting part to the pelvic floor.
b. Expulsive phase-is distinguished by maternal bearing down
efforts and ends with delivery of the baby.

3. • Its average duration is 2hours in primigravida and 30minutes in
multipara.
• This period is typically characterized by maternal restlessness,
discomfort, desire for pain relief, a feeling that the process is never
ending and demands to birth attendants to get the birth process over
as quickly as possible.

4. Principles of second stage of labor
 To assist in the natural expulsion of the fetus slowly and steadily
 To prevent perineal injuries.

5. Physiology of second stage of labor
• The physiological changes result from a continuation of the
same forces that have been at work during the first stage of
labor but activity is accelerated once the cervix has become
fully dilated.
 UTERINE ACTION:
• contractions become stronger and longer but may be less
frequent, allowing both mother and fetus to rest in between
contractions.

6. • The membrane often rupture spontaneously towards the end of
the first stage during transition to the second stage.
• The consequent drainage of liquor allows the fetal head to be
directly applied to the cervix, this pressure aids distension.
• Fetal axis pressure increases flexion of the head, which results
in smaller presenting diameters, more rapid progress and less
trauma to both mother and fetus.

7. FETAL AXIS PRESSURE

8. • The contractions become expulsion as the fetus descends
further into the vagina.
• Pressure from the presenting part stimulates nerve receptors in
the pelvic floor (ferguson reflex) and the women experiences
the urge to push.
• The reflex may initially be controlled to a limited extent but
becomes increasingly compulsive, overwhelming and
involuntary during each contraction.

9. • The mother then employs her secondary powers of expulsion
i.e. the abdominal muscles and diaphragm to push out the baby.
 SOFT TISSUE DISPLACEMENT:
• The descending fetal head displaces the soft tissues of the
pelvis.
• Anteriorly, the bladder is pushed upwards into the abdominal
cavity where it is at less risk of injury during fetal descent.
• This results in the stretching and thinning of the urethra.

10. • Posteriorly, the rectum becomes flattened into the sacral curve
and the pressure of the advancing head expels any residual
faecal matter.
• The levatoani muscles dilate, thin out and are displaced laterally
and the perineal body is flattened, stretched and thinned.
• The fetal head becomes visible at the vulva, advancing with
each contraction and receding between contractions until
crowning takes place.

11. Levatoani muscle

12. Perineal body

13. • The head is then born and the shoulders and body follow with the
contraction accompanied by a gush amniotic fluid and sometimes
blood.
• The second stage culminates in the birth of the baby.

14. Recognition of the commencement of the second
stage
This is not clinically apparent. Several of the signs are
presumptive and can only be confirmed by vaginal examination.
These include:
 Expulsion uterine contractions: Although this is usually a sign
that the cervix is fully dilated, it is possible for the women to feel
the urge to push before full dilatation occurs e.g. when rectum is
full, etc..

15.  Rupture of forewaters: This may occur at anytime during labor but
physiologically, it occurs at the end of 1st stage when cervix is fully
dilated and can no longer support the bag of waters.
 Dilatation & gaping of the anus: As the fetal head descends and
touches the pelvic floor, there’s increased pressure especially on the
rectum. This results in dilation and gaping of the anus and may result in
discharge of faecal matter.

16. Dilatation AND GAPING OF THE ANUS

17.  Appearance of the presenting part: Although this is usually definitive,
it is important to be aware that excessive moulding may result in the
formation of a large caput succedaneum, which can protrude through
the cervix prior to full dilatation. Similarly, a breech presentation may be
visible when the cervix is not fully dilated.

18. MOULDING OF THE HEAD CAPUT SUCCEDANEUM

19.  Show: this is the loss of bloodstained mucus which often
accompanies rapid dilatation towards the end of 1st stage of
labor. It must be distinguished from frank fresh blood loss
caused by partial separation of the placenta, or that caused by
ruptured vasa previa.
 Congestion of the vulva: the pressure of the fetal head on the
vulva results in venous congestion, however, premature
pushing may also cause this.

20. VASA PREVIA

21. COMFIRMATORY EVIDENCE
 This is only done by vaginal examination which reveals no cervix and it
is done to:
 Ensure the women is not pushing too early before the cervix is fully
dilated.
 To provide a baseline for timing the length of 2nd stage of labor.

22. Principles of mechanism of labor
• Descent takes place throughout the labor.
• Whichever part leads and first meet the resistance of the
pelvic floor will rotate until it comes under the symphysis
pubis.
• Whatever emerges from the pelvis will pivot around the
pubic bone.

23. mechanism of labor
Definition:
The series of movement that occur on the head in the process of
adaptation, during its journey through the pelvis is called
mechanism of labor.
At the onset of labor, the most common presentation is the vertex
and most common position either left or right occipitoanterior;
therefore it is this mechanism which will be described.

24. • In this instance:
 The lie is longitudinal.
 The presentation is cephalic.
 The position is right or left occipito-anterior
 The attitude is one of good flexion
 The denominator is the occiput
 The presenting part is the posterior part of the anterior parietal
bone.

25. Main movement of fetus
• Engagement
• Descent
• Flexion
• Internal rotation
• Crowning
• Extension of the head
• Restitution
• External rotation
• Birth of the shoulder and trunk

26. Engagement
• When the bi-parietal diameter of the head passes the pelvic
inlet, the head is said to be engaged.
• In the most nulliparous pregnancies this occurs before the onset
of active labor because the firmer abdominal muscle directs the
presenting part into the pelvis.
• In multiparous pregnancies, in which the abdominal
musculature is more relaxed, the head often remains freely
movable above the pelvic brim until labor is established.

30. Engagement of the head

31. Diameters of skull

32. Descent
• Following engagement, descent of the head occurs. In fact
descent is a continuous process occurring throughout the labor
till the head is born.
• Descent of the fetal head into the pelvis often begins before the
onset of labor. For a primigravida women this usually occurs
during the later weeks of pregnancy.
• In multigravida women muscle tone is often more lax and
therefore descent of the fetal head and engagement of the fetal
may not occur until labor actually begins.

33. • Throughout the first stage of labor the contraction and retraction of the
uterine muscles allow less room in the uterus, exerting pressure on the
fetus to descend further.

34. Flexion
• As soon as head meets resistance from the cervix, pelvic wall or pelvic
floor during descent, full flexion is achieved.
• Flexion is essential for descent, since it reduces the shape and size of
the plane of the advancing diameter of the head.

36. Internal rotation:
• The occiput rotates anteriorly and the fetal head assumes an oblique
orientation.
• It is a movement of great importance without which there will be
no further descent.
It is probably due to slope of pelvic floor, pelvic shape and
inequalities in flexibility
of component parts of the fetus. Torsion of the neck is an
inevitable phenomenon
during internal rotation of head. There is no movement of the
shoulders from the
oblique diameter as the neck sustains a torsion of only 1/8th of a
circle.

37. Crowning
• After internal rotation of the head, further descent occurs until the sub-
occiput lies underneath the pubic arch. At this stage, the maximum
diameter of the head (bi-parietal) stretches the vulval outlet without any
recession of the head even after the contraction is over called crowning
of the head.

39. Extension of the head
Once crowning has occurred the fetal head can extend, pivoting on the
sub-occipital region around the pubic bone. This releases the sinciput,
face, and chin, which sweep the perineum, and then are born by a
movement of extension.

41. Restitution
the twist in the neck of the fetus which resulted from internal rotation is
now corrected by a slight untwisting movement. The occiput moves 1/8 of
a circle towards the side from which it started.

42. External rotation
It is movement of rotation of the head visible externally due to internal
rotation of the shoulders. As the anterior shoulder rotates toward the
symphysis pubis from the oblique diameter, it carries the head in a
movement of external rotation through 1/8th of a circle in the same
direction as restitution.

43. Birth of shoulder and trunk
After the shoulders are positioned in anteroposterior diameter of the
outlet, further descent takes place until anterior shoulder escapes below
the symphysis pubis first, by a movement of lateral flexion of the spine,
the posterior shoulder sweeps over the perineum. Rest of the trunk is
then expelled out by lateral flexion.

44. Management of second stage of labor
The transition from the first stage to the second stage is
evidenced by the following features:
Increasing intensity of uterine contractions
Appearance of bearing down efforts.
Urge to defecate with descent of the presenting part.
Complete dilatation of the cervix as evidenced on vaginal
examination.

45. Aims of management of second stage of labor
• To deliver the baby safely in healthy condition.
• To prevent maternal injuries like perineal tear.
• To prevent infection during the conduct of delivery.

46. Constant monitoring of the mother and fetus
• Maternal pulse and BP are frequently recorded.’
• FHR are monitored every 5 minutes
• Vaginal examination is done to note the status of membrane, color of
the liquor and to detect cord accident following rupture of membranes if
any. Presentation, position and progressive descent of fetus are also
noted.

47.  Position: The common preferred position is dorsal with
15degree lateral tilt. Patient may vary according to the patient’s
choice.
 The accoucheur scrubs up and puts on sterile gown, mask
and gloves and stands on the right side of the table.
 Toileting the external genitalia and inner side of the thighs is
done with cotton swabs soaked in savlon or Dettol solution. On
sterile sheet is placed beneath the buttocks of the patient and
one over the abdomen.

48. Essential aseptic procedure are remembered as 3 ‘C’:
 Clean hands
 Clean surface
 Clean cutting and ligaturing of the cord.

49.  Catheterization: catheterize the bladder if it full.
 Examination of the patient: After the catheterization, the patient is
again examined per abdominally and vaginally.

50. CONFIRM ESSENTIAL SUPPLIERS ARE AT BEDSIDE
AND PREPARE FOR DELIVERY
 For mother:
• Gloves
• Alcohol-based hand rub or soap and clean water.
• Oxytocin 10 units in syringe.
 For baby:
• Clean towel.
• Tie or cord clamp.
• Sterile blade to cut cord.
• Suction device.
• Bag-and-mask.

51. The assistance required in spontaneous delivery is divided into three
phases:
DELIVERY OF HEAD:
 The patient is encouraged for the bearing down efforts during uterine
contractions. This facilitates descent of the head.
 When the scalp is visible for about 5cm in diameter, flexion of the head
is maintained during contractions.

52.  This is achieve by pushing the occiput downwards and
backwards by using thumb and index fingers of the left hand
while pressing the perineum by the right palm with a sterile
vulval pad.
 If the patient passes stool, it should be cleaned and the region
is washed with antiseptic lotion.
 the process is repeated during subsequent contractions until
the sub-occiput is placed under the symphysis pubis. At this
stage, the maximum diameter of the head (biparietal diameter)
stretches the vulval outlet without any recession of the head
even after the contraction is over and it is called “crowning of
the head”.

53.  When the perineum is fully stretched and threatens to tear specially
in primigravida, episiotomy is done at this stage after prior infiltration
with 10ml of 1% lignocaine. Bulging thinned perineum is better
criteria. Episiotomy is selectively and not as a routine.
 The forehead, nose , mouth and the chin are born successively over
the stretched perineum by extension.

54. Care following delivery of the head
 Immediately following delivery of the head, the mucus and
blood in the mouth and pharynx are to be wiped with sterile
gauze piece on a little finger. Alternatively, mechanical or
electrical sucker may be used. This simple procedure prevents
the serious consequences of mucus blocking the air passage
during vigorous inspiratory efforts.
 The eyelids are then wiped with sterile dry cotton swabs using
one for each eye starting from the medial to the lateral canthus
to minimize contamination of the conjunctival sac.

55.  The neck is then palpated to exclude the presence of any loop of cord
(if it found and if loose enough, it should be slipped over the head or
over the shoulders as the baby is being born. But it is sufficiently tight
enough, it is cut in between two pairs of Kocher’s forceps placed 1 inch
apart.

56. Prevention of perineal laceration
 More attention should be paid not to the perineum but to the
controlled delivery of the head.
• Delivery by early extension is to avoided: flexion of the sub-
occiput comes under the symphysis pubis so that lesser sub-
occipitofrontal 10cm (4’’) diameter emerges out of the introitus.
• Spontaneous forcible delivery of the head is to be avoided by
assuring the patient not to bear down during contractions.

57. • To deliver the head in between contractions.
• To perform timely episiotomy (when indicated).
• To take care during delivery of the shoulders as the wider bisacromial
diameter (12cm) emerges out of the introitus.

58. DELIVERIES OF THE SHOULDERS
 Wait for the uterine contractions to come and for the
movements of restitution and external rotation of the head to
occur. Following restitution and external rotation of the head,
the shoulders (bisacromial diameter) come in anteroposterior
diameter of the pelvis.
 During next contraction, the anterior shoulder is born behind the
symphysis pubis. If there is delay, the head is grapsed by both
hands and is gently drawn posteriorly until the anterior shoulder
is released from under the pubis.

59.  By drawing the head in upward direction, the posterior shoulder is
delivered out of the perineum.
 Traction on the head should be gentle to avoid excessive stretching of
the neck causing injury to the brachial plexus, hematoma of the neck or
fracture of the clavicle.

60. DELIVERY OF THE TRUNK
 After the delivery of the shoulders, the fore fingers of each hand are
inserted under the axillae and the trunk is delivered gently by lateral
flexion.

61. References
• https://www.slideshare.net/rabimohd07/the-second-stage-of-
labour
• Dc Dutta’s, 7th edition, Textbook of obstetrics, Jaypee brothers
medical publishers page no:123-126,135-137
• Arup Kumar Majhi, 2nd edition, Bedside clinics in obstetrics,
academic publishers. Page no: 377-380
• Myles, 5th edition, Textbooks of Midwives. Page no:515-516]
• Durga Subedi, Saraswoti Gautam, midwifery nursing part-II.
Page no: 69-71