Repro19 - Labour & Delivery

Question 1

Definition of labour, delivery and parturition

Answer 1

1. ) Labour - physiological process by which a fetus is expelled from the uterus to the outside world
2. ) Delivery - the method of expulsion of the fetus, transforming the fetus into a neonate
3. ) Parturition - transition from pregnant to non-pregnant state (birth)

Question 2

4 features of the first stage of labour

Physiological
Clinical
Latent Phase
Active Phase

Answer 2

1. ) Physiological - creation of the birth canal and descent of the fetal head into it
   - casued by multiple physiological changes

2.) Clinical - interval between onset of labour and full cervical dilation (10cm)

3. ) Latent Phase - onset of labour w/ slow cervical dilation but softening
   - lasts a variable amount of time

4.) Active Phase - regular contractions and faster rate of change

Question 3

4 features of the second stage of labour

Physiological x3
Clinical
Passive Movement
Active Movement

Answer 3

1. ) Physiological
   - changes in uterine contractions to expulsive
   - descent of the fetus through birth canal and delivery
   - adaptations of the fetus to independent life
2. ) Clinical - interval between full cervical dilation and delivery of the fetus
3. ) Passive Movement - descent and rotation of the head
4. ) Active Movement - maternal pushing to expel the fetus out the birth canal and achieve birth

Question 4

3 features of the third stage of labour

Physiological x2
Clinical
Time Period

Answer 4

1. ) Physiological
   - expulsion of the placenta
   - contraction of the uterus

2.) Clinical - interval from full delivery to complete expulsion of the placenta and membranes

3. ) Time Period - usually lasts 5-15 minutes
   - may last 30-60 mins depending on circumstances

Question 5

4 features of the role of prostaglandins and oestrogen in labour

Synthesis of Prostaglandins
Function of Prostaglandins
Increase in Contractility
Cervical Ripening

Answer 5

1. ) Synthesis of Prostaglandins - stimulated by increase in oestrogen (oestrogen:progesterone ratio)
   - made by the placenta, decidua, myometrium
   - increased synthesis by amnion in 3rd trimester
2. ) Function of Prostaglandins - stimulates contractions
   - progesterone causes inhibition of contractions since fall in progesterone (O:P) = less prostaglandin synthesis
   - artificial prostaglandins or anti-progesterone agents given initially to try and induce labour
3. ) Increase in Contractility - caused by oestrogen
   - increases gap junctional communication betwen SMCs
   - stretching of uterine SM also increases contractility
4. ) Cervical Ripening - oestrogen and prostaglandins
   - relaxin is also involved

Question 6

4 features of the role of oxytocin in labour/pregnancy

Function
Inhibition
@36 weeks
Ferguson’s Reflex

Answer 6

1. ) Function - initiates uterine contractions
   - acts on smooth muscle receptors
   - more oestrogen (O:P) = more receptors
   - synthetic oxytocin can be given to induce labour
2. ) Inhibition - occurs during pregnancy
   - due to progesterone and low no of oxytocin receptors
3. ) @ 36 weeks - contractions can start to occur
   - increased no. of oxytocin receptors in the myometrium
   - uterus can respond to pulsatile release of oxytocin from the posterior pituitary gland
4. ) Ferguson’s Reflex - postive FB w/ oxytocin release
   - oxytocin –> contractions –> more oxytocin
   - cycle breaks once the fetus is delivered

Question 7

5 features of cervical ripening before labour

Reason
Hormonal Influences x3
Chemical Changes x2
Effacement
Dilation

Answer 7

1. ) Reason - cervix initially needs to be tough and thick to retain the fetus for most of pregnancy
   - during labour, the cervix needs to soften (ripen) to make labour easier

2.) Hormonal Influences - oestrogen, prostaglandins (PGE2 and PGF2-alpha), and relaxin

3. ) Chemical Changes
   - collagenase degrades collagen and collagen fibrils
   - increase in GAGs and hyaluronic acid
4. ) Effacement - thinning of the cervix
   - occurs due to forceful contractions of uterine SM (brachystasis)
5. ) Dilation - widening of the gap between the cervix
   - occurs after effacement

Question 8

3 features of the birth canal during pregnancy

Maximum Size
Normal Presentation
Pelvic Floor

Answer 8

1. ) Maximum Size - determined by the pelvis
   - pelvic inlet typically 11 cm wide
   - softening of ligaments may increase it
2. ) Normal Presentation - longitudinal lie w/ flexion
   - head is largest part and diameter is usually 9.5cm

3.) Pelvic Floor - levator ani muscles stretch and perineum thins to an almost transparent structure

Question 9

4 features of the uterine smooth muscle (myometrium) during labour

Contraction and Retraction
Generating Force
Control of Contractility
Braxton Hicks Contraction

Answer 9

1. ) Contraction and Retraction (brachystasis)- myometrial fibres contract but only partially relax
   - permanent partial shortening of the muscles fibres
   - uterine capacity reduces so pressure inside the uterus becomes stronger to aid delivery
2. ) Generating Force - rise in intracellular [Ca2+]
   - action potentials are spontaneously triggered
   - the myometrium is much thickened in pregnancy
3. ) Control of Contractility
   - prostaglandins increases Ca2+ per AP so contractions are made more forceful and frequent
   - oxytocin lowers the threshold so more APs fired
4. ) Braxton Hicks Contractions - ineffective contractions as they don’t actually push the baby out
   - becomes brachystasis when it gets stronger

Question 10

3 features of common fetal presentations in the uterus

Lie
Attitude
Breech

Answer 10

1. ) Lie - longitudinal (most common) or transverse
   - longitudinal: long axis of fetus and mother are parallel
   - transverse: long axis’ are perpendicular
2. ) Attitude - position of the head and limbs
   - flexion: head, arms and legs flexed tightly (normal)
   - extension: head is extended and an arm may also be extended
3. ) Breech - orientation of the fetus
   - frank breech: bottom faces the cervix with legs lying over the head (most common)
   - full breach: bottom faces the cervix with legs and arms tucked inside the trunk
   - footling breech: foot sticking out the cervix

Question 11

4 stages of the process of normal delivery (2nd stage of labour)

Answer 11

1. ) Flexion and Internal Rotation - of the head
   - baby is now facing backwards

2.) Crowning - head stretches perineal muscle and skin

3. ) Extension and External Rotation - of the head
   - external rotation is also called restitution

4.) Completion - shoulder rotate and are delivered followed rapidly by the body

Question 12

2 ways delivery can be facilitated by intervention

Answer 12

1.) Cesarean Section - delivery of baby via an abdominal incision through the skin and uterus

2. ) Operative Delivery - assisted vaginal delivery
   - forceps can be used but poor usage can lead to Erb’s palsy or a facial nerve palsy

Question 13

3 processes limiting maternal blood loss after delivery

Importance of controlling bleeding

Answer 13

1. ) Uterus Contraction - constrict blood vessels running through the myometrium
   - especially action of interlacing muscle fibres
2. ) Apposition - pressure exerted on placental site by walls of the contracted uterus
   - occurs once placenta and membranes are delivered

3.) Blood Clotting Mechanisms

4. ) Importance - normal blood flow through placental site is 500-800ml/min (10-15% of cardiac output)
   - processes prevent significant blood loss

Question 14

2 physiological changes in the neonate to adapt to independent life

Cardiovascular
Respiratory

Answer 14

1. ) Cardiovascular - clamping the umbilical cords closes the ductus venosus
   - the remaining shunts go on to close aswell
2. ) Respiratory - first breath causes lungs to expands
   - alveoli inflate and inflation maintained by surfactant
   - if baby doesn’t breathe, mimic lung expansion