Pregnancy and birth

Question 1

Factors that initiate birth

Answer 1

Hormonal changes
- Fetal and maternal

Mechanical changes

Decidua release of prostaglandins

Question 2

Hormonal initiation of labour [5]

Answer 2

Fetal hypothalamus triggers activation of maternal hormonal release

Fetal cortisol triggers placental hormone release

Rise in oestrogen, drop in progesterone

Oxytocin from posterior pituitary + prostaglandins from decidua= uterine contractions

Question 3

Mechanical stimulation during labour

Answer 3

Overstretching and pressure causes baby to mechanically stimulate the uterus and cervix

Question 4

Latent phase labour

Answer 4

Length: hours to days

Cervical effacement
- Thinning of the cervix

Contractions of varying intensities

Question 5

Cervical effacement

Answer 5

The thinning of the cervix that initiates during latent labour.

The cervix starts at a bottle neck shape, 4cm long, then thins and widens
- When the cervix is not palpable, it is fully dilated.

Question 6

Second stage of labour

Answer 6

Delivery of the baby after full dilatation (10 cm)

Question 7

Anteroposterior diameter of pelvic brim

Answer 7

12cm

During labour the baby’s head transverses the oval pelvic brim

Question 8

Diameters of the pelvic outlet

Answer 8

Outlet is diamond shape

Anteroposterior diameter

• 12.5cm wide
• Space available for the baby;s delivery
• Coccyx moves backwards during birth

Oblique diameter

Transverse diameter
- Space between the ischial spines.

Question 9

Occiptofrontal diameter

• Description
• Length
• Function

Answer 9

The diameter between the frontal and occipital bone
- 11cm

Delivery via this diameter is more difficult

• Baby’s head is extended
• Anterior fontanelle is visible.

Question 10

Suboccipitobregmatic 
diameter
- Description
- Length
- Function

Answer 10

The length between the anterior (bregma) fontanelle and occipital bone
- Line below posterior fontanelle.

9. 5 cm
   - Most ideal fetal position for childbirth
   - Head is flexed, only posterior fontanelle visible.

Question 11

Anterior fontanelle closes at …

Answer 11

18 months

Question 12

Posterior fontanelle closes at …

Answer 12

6-8 weeks

Question 13

Supraocciptomenal diameter

• Description
• Length
• Importance

Answer 13

The length between the mental bone (chin) and occipital bone
- Line above posterior fontanelle

13.5cm

Least ideal position for the baby to be born in (brow position)

• Most likely convert to C-section
• Anterior fontanelle visible

Question 14

Submentobregmatic diameter

• Description
• Length
• Importance

Answer 14

The length between the mental bone and bregma fontanelle

9.5cm

Baby is born in ‘face’ position

Question 15

OT position

Answer 15

Occipital-transverse positon

When the baby’s head is facing the mother’s thigh (occipitofrontal)

Question 16

Mechanism of birth

Answer 16

1. Head descends to pelvic brim in OT position.
2. Flexion of the head showing suboccipitobregmatic diameter
3. Head descends further and reaches pelvic floor.
4. Head rotates to OA position and is delivered by extension.
5. Head comes in line with the shoulders (restitutes)
   - Shoulders rotate to AP diameter of pelvis
6. Anterior shoulder delivered by downwards lateral flexion of baby’s head
7. Posterior shoulder delivered by upwards lateral flexion.

Question 17

OA position

Answer 17

Occipital-Anterior position

Baby’s face is facing towards the back of the mother

Question 18

Third stage of labour

Answer 18

Delivery and inspection of the placenta

Blood loss
- 300-500ml

Question 19

Things inspected after placental delivery

Answer 19

Position of umbilical cord

• Marginal?
• Velamentous?
• 2 arteries and a vein?

Complete umbilical cord
- Left over in uterus can cause inflammation

Checking the membranes

• Amniotic
• Chorionic

Question 20

Placental delivery

Answer 20

Can either be physiological

• After breastfeeding
• Release of oxytocin stimulates uterine contraction= expulsion of placenta

Active management

• Oxytocin given i.m
• Decreases placental bleed and post-haemorrhage

Question 21

Intermittent auscultation

Answer 21

Done using a pinard/ sonicaid

First stage of labour
- Fetal heart beat listened 15 mins before and after contraction

Second stage
- Every 5 mins

Any abnormality= CTG use

Question 22

CTG

Answer 22

Cardiotocograph
- Monitors uterine contractions corresponding to fetal heart rate

Abdominal ultrasound–> cardiac movements (more common)

OR

Clip attached to fetal scalp (FSE)
- Detects R-R wave in fetus

Very sensitive but not specific

Question 23

Fetal blood sampling

Answer 23

Used as a more specific measure after CTG
- Checks findings found in CTG

Fetal scap stabbed and blood sample collected with capillary pipette
- pH and base excess calculated

Question 24

Contraindications of FBS

Answer 24

Infections
- HIV, Hep B

Fetal bleeding disorder
- Haemophilia

Prematurity <32 weeks.