L22 Pregnancy and Birth

Question 1

Initiation of labour overview

Answer 1

Remains uncertain

Multifactorial in origin

• hormonal
• mechanical

Foetal hypothalamus is triggered

Maternal post pituitary releases oxytocin

Decidua releases prostaglandins

Question 2

Initiation of labour (hormones)

Answer 2

Increase in oestrogen pro-labour hormone

Decrease in progesterone pro-pregnancy hormone

Release of oxytocin by the mother’s posterior pituitary gland

Prostaglandins from the decidua

Together creating uterine contractions

Mechanical stimulation of the uterus and cervix caused by overstitching and pressure from the posterior pituitary

Question 3

Stages of labour

Answer 3

Latent phase

1st stage of labour

2nd stage of labour

3rd stage of labour

Question 4

Latent phase of labour

Answer 4

Effacement of cervix

Contractions

Intensity varies

Question 5

Effacement of the cervix

Answer 5

Before labour 0% effacement

Early effacement 30%

Complete effacement 100%

Complete dilation

Question 6

Diagnosis of active labour

Answer 6

Painful regular contractions

Cervical effacement

Dilation of the cervix of 4cms or more

Question 7

Active labour/first stage of labour

Answer 7

Established labour to full cervical dilation

Vaginal examinations

Average is 0.5cm/hour

Question 8

Descent of the foetal head in relation to the ischial spines

Answer 8

Progress measured by dilatation and descent of the foetal head (in relation to the pelvic brim and ischial spines)

Question 9

Second stage of labour

Answer 9

From full dilatation to the delivery of the baby

Question 10

Pelvic inlet

Answer 10

The brim is oval except where the promontory projects

The anteroposterior diameter is 12cm

Question 11

Pelvic outlet

Answer 11

The outlet is diamond shaped

Its 3 diameters are:

• anteroposterior (as the coccyx is deflected backwards this is the space available during birth)
• oblique
• transverse

Question 12

Fontanelles

Answer 12

Anterior fontanelle (bregma)

• diamond shaped intersection of 4 sutures
• 2x3cms
• closes at 18 months

Posterior fontanelle

• Y shaped intersection of 3 sutures
• closes at 6-8 weeks

Question 13

Diameters of the foetal skull

Answer 13

Suboccipitobregmatic (9.5 cms) = OA position

Occipitofrontal (11 cms) = OP position

Supraoccipitomental (13.5 cms) = brow

Submentalbregmatic (9.5 cms) = face

Question 14

Mechanism of birth

Answer 14

Head at pelvic brim Occipital transverse (OT) position

Flexion of neck (suboccipitobregmatic)

Head descends and engages

Head reached pelvic floor - rotates to occipital anterior

Head delivers by extension

Head ‘restitutes’ (comes in line with shoulders)

Shoulders rotate into anterior/posterior diameter of pelvis

Anterior shoulder delivered by lateral flexion from downward pressure on baby’s head

Posterior shoulder by upward lateral flexion

Question 15

Third stage of labour

Answer 15

Delivery of placenta

Normal estimated blood loss 300-500mls

Inspection of placenta to ensure complication

Question 16

2 methods in third stage of labour

Answer 16

1. Active management (CTT)
   Oxytocin i.m. given into maternal thigh
   -cause sustained uterine contraction
   -aids delivery of the placenta and contraction of the placental bed
   -decreases risk of post part haemorrhage (PPH)
2. Physiological: mother naturally expels the placenta and membranes with contractions

Question 17

Foetal monitoring in labour

Answer 17

To detect foetal hypoxia and deliver baby if needed

Screening the foetal heart rate by

• intermittent auscultation by Pinard or Sonicaid
• CTG (cardiotocograph)
• FBS

Question 18

Intermittent auscultation

Answer 18

Every 15 mins before and after a contraction during the first stage

Every 5 mins in the second stage

Any abnormality heard would lead to the use of CTG

Question 19

Cardiotograph

Answer 19

Continuous print out of the foetal heart rate and contractions
-abdominal ultrason
=>detects cardiac movements and hence HR
-a clip applied to the foetal scalp (FSE)
=>detects the R-R wave of the foetal ECG

Most usual is the abdominal ultrasound

Question 20

Foetal Blood Sampling

Answer 20

CTG is highly sensitive e.g. if normal, baby is ok
But poorly specific e.g. if abnormal only a few babies are hypoxic

Use of CTG less to a 4 fold increase in Caesareans Sections for foetal distress THEREFORE need to check the CTG findings with FBS

Question 21

How FBS is done

Answer 21

Stab on the foetal scalp

Blood collected via a glass pipette

pH and base excess result

Question 22

Contraindications of FBS

Answer 22

Infection such as HIV, Hepatitis B

Foetal bleeding disorder

Prematurity less than 32 weeks