Lecture 4 - Parturition

Question 1

What does the placenta do and how does it form?

Answer 1

haemochorial placentation
effective from end of first trimester
senesces as pregnancy progresses
large reserve
-responsible for - hormone production, preferential acquisition nutrients and removal of toxins
-gas exchange (CO2, O2)

Question 2

placenta function

Answer 2

consists of a few layer of cells
large surface area
-folding villi

Question 3

Explain the saturation of fetal and maternal haemoglobin at different partial pressures

Answer 3

At lower partial pressures below 80% - foetal haemoglobin has a greater affinity for oxygen
under optimal conditions - maternal and fetal haemaglobin has the same o2 saturations.

Question 4

Increased foetal oxygen content is due to

Answer 4

higher Hb concentrations
higher affinity for O2
further left shift 
- reduced binding of DPG to fetal hb
- Increased pCO2 and relative acidosis on maternal side (right shift)

Question 5

Role of surfactant in the fetal lung

Answer 5

from 24 weeks of pregnancy - produced by type 2 pneumocytes
produced surfactant
mixture of phospholipids (PC and PG) and apoproteins (SP-A,B,C,D)
decreases surface tension at air-liquid interface in the alveoli - remain open during expiration

Question 6

What stimulates release of fetal surfactant

Answer 6

stimulated by fetal glucocorticoids and thyroid hormones

Question 7

Lack of surfactant

Answer 7

leads to neonatal respiratory distress

replace in neonatal period - curosurf

Question 8

Myometrial activity

Answer 8

rise in membrane potential
increased intercellular coupling
mechanical/endocrine/paracrine influences

Question 9

Diagnosis of labour

Answer 9

regular painful contractions
progressive effacement and dilation of uterus
descent and presenting of the part

Question 10

Endocrine effects

Answer 10

production of cytokines, prostaglandins, oxytocin facilitate labour
progesterone, estrogen,
increased DHEAS, CRH, progesterone and estrogens

Question 11

causes for preterm labour

Answer 11

uterine capacity
placental abruption
cervical weakness
infection - local/systemic
triggers release of cytokines

Question 12

Birth asphyxia (oxygen compromised)

Answer 12

compression of myometrial arteries
cessation of flow to placenta
lack of gas exchange
relative fetal hypoxia
anaerobic metabolism -lactic acidosis

Question 13

Consequences of birth asphyxia

Answer 13

lactic acidaemia
tissue acidosis
hypoxic - ischemic encephalopathy
cerebral palsy
fetal distress more likely 
- low birth weight
long labout
impaired placental function

Question 14

Management of birth asphyxia

Answer 14

fetal heart rate monitoring
measurement of fetal scalp pH
monitor ST segment changes
expedite delivery by cesarean section or forceps
prognosis good if cord arterial pH > 7 and base excess better than - 12 mmol/l