Reproduction: Parturition and lactation

Question 1

What is parturition?

Answer 1

Birth

Question 2

What is lactation?

Answer 2

Milk production in the mammary glands

Question 3

What are the stages of parturition? (4)

Answer 3

• Positioning of the fetus
• Head first on the cervix
• breeched is feet-first (5%)
  
  • half of these will kick around in labour

Question 4

What occurs in the first stage of labour? (6)

Answer 4

• Up to 24hrs
• Dilation of the cervical canal to accommodate fetus
• Fetus bears down head first, amniotic sac is broken - waters breaking
• Waters breaking act as a lubricant
• Increased myometrial contractions, expel fetus
• Braxton-Hicks contractions become more coordinated

Question 5

What occurs in the second stage of labour? (6)

Answer 5

• 30-90mins duration
• Cervical dilation is complete
• Head of fetus activates cervical stretch receptors
• Synchronised abdominal and uterine contractions
• 3min intervals, 60s duration
• Baby delivered, umbilical cord tied and severed

Question 6

What occurs at the 3rd stage of labour? (4)

Answer 6

• 30mins
• Second series of myometrial contractions, expel placenta
• Prevents excessive haemorrhage
• Loss of placenta causes a major fall in hormones

Question 7

What is the fetal response to parturition? (2)

Answer 7

• Elevated levels of O2 in fetal circulation

- Fetal supply of O2 to placental circulation

Question 8

How is parturition regulated? (5)

Answer 8

Positive feedback loop:

• Cervical stretch
• Oxytocin from posterior pituitary
• Prostaglandins from uterine wall
• Uterine contractions
• Cervical stretch

Question 9

How is Parturition triggered? (3)

Answer 9

Fetal placenta: CRH -> fetal ACTH -> DHEA
DHEA -> estrogens (enters bloodstream)
Estrogen –> parturition

Question 10

What is placental corticotrophin releasing hormone? (3)

Answer 10

• Placental levels increase during pregnancy
• Placenta is the principle source
• Regulates fetal adrenal production of DHEA sulphate

Question 11

What is the pharmacology of pregnancy? (4)

Answer 11

• Uterine muscle characterised by electrical activity
• Can be modified by humeral and neuronal factors
• Spread of excitation occurs via low resistance contacts
• Therapeutic agents either increase intracellular calcium

Question 12

What are spasmogens? (3)

Answer 12

• Increase force and frequency of contractions
• Oxytocin
• Prostaglandins

Question 13

What are the clinical uses of spasmogens? (3)

Answer 13

• Induce or augment labour
• Control post-partum uterine haemorrhage
• Induce therapeutic abortion

Question 14

What is the role of relaxants? (3)

Answer 14

• Reduce frequency and force of contractions
• B2 adrenoreceptor agonists
• Magnesium ions

Question 15

What are the clinical uses of relaxants? (3)

Answer 15

• Delay or prevent premature parturition
• 7 days
• Slow or arrest delivery to undertake therapeutic measures

Question 16

What inhibits and stimulates lactation? (2x2)

Answer 16

Inhibit: estrogen, progesterone
Stimulate: Prolactin, oxytocin

Question 17

What is lactation made up of? (2)

Answer 17

Colostrum - watery milk, lots of protein

Later milk - nutrients, hormones, growth factors, antibodies

Question 18

What stimulates milk synthesis?

Answer 18

Prolactin

Question 19

What stimulates milk ejection reflex?

Answer 19

Oxytocin

Question 20

What are the advantages of breast feeding? (3)

Answer 20

• Oxytocin release hastens uterine involution
• Suckling surprises menstrual cycle by inhibiting LH and FSH
• Acts as a natural contraceptive

Question 21

What is the cessation of milk production at weaning? (3)

Answer 21

• In the absence of suckling, prolactin is not stimulated
• No suckling leads to no oxytocin release
• Milk production does not immediately shut down, pressure builds