Pregnancy and lactation

Question 1

Describe the trend in foetal growth

Answer 1

• slow growth until week 20 (as placenta is not fully formed until week 12 so no adequate nutrition)
  slight increase in weight comes from cell number and cell differentiation into organs
• maximum growth weeks 30-36
• growth rate slows after week 36 (as placenta size and blood flow become limiting factors

Question 2

Factors involved in foetal growth

Answer 2

influenced by
- nutrition
(mainly malnutrition - which leads to severely underweight babies)

• sex (male foetuses usually heavier - could be hormones)
• foetal genome
• circulating foetal and maternal factors
  (IGF which when knocked out causes slowing of growth)

Question 3

How does maternal metabolism change during pregnancy

Answer 3

early pregnancy
- increased fat stores, increased protein sysnthesis, decreased fasting glucose

late pregnancy
- impaired insulin sensitivity
(results in less insulin being taken into cells)
- enhanced beta-cell response

this results in increased availability of glucose to support growing foetus (maternal cells switch to use fatty acids)

Question 4

Morning sickness during pregnancy

Answer 4

• hyperemesis gravidarum (extreme) in 0.5% of people
• morning sickness occurs in around 80% of people

unknown cause
- thought to be a protective effect to rid the body of tetratogens (any agent that can cross to foetus and can damage)
- or effect of hormones (thought to be hCG as a new hormone with increased levels)

no correlation found yet so unknown

Question 5

What are the general maternal changes during pregnancy

Answer 5

• tidal volume increases (as more O2 needed for increased metabolism)
• blood volume can increase by up to 40% (blood to foetus)
• cardiac output rises by 30-40% (heart enlarges to pump more blood)
• increased urine production (more liquid to filter but reduced bladder size so need to urinate more)

Question 6

Hormone changes during pregnancy

Answer 6

normal cycle: oestrogen and progesterone levels decline as corpus luteum degenerates

during pregnancy:
hCG - needed up to week 10 to maintain corpus luteum secreted from trophoblast

hPL - results in breast growth (peaks at week 40 just before birth)

Question 7

Progesterone and oestrogen use during pregnancy

Answer 7

progesterone
- stimulates endometrial thickening and encourages successful implantation
- helps placental development
- maintains quiescent uterus (inactive so no contractions)

• found that in mice stress induced abortion can be reduced with injection of dydrogesterone
• but inconclusive evidence to support this

oestrogen
- controls other pregnancy hormones
- encourages growth of uterus and breasts
- increases sensitivity of myometrium

Question 8

How is parturition (labour) initiated

Answer 8

physical
- increased stretching of myometrium, placental insufficiency and inflammation (signals that size of foetus can support itself outside the body)

endocrine
- maturation of foetal hypothalamus and pituitary glands

hypothalamus —> (CRH) anterior pituitary —> ACTH) adrenal glands —> (cell growth is completed) foetal bloodstream —> CORTISOL

CORTISOL
- encourages organ development and release of surfactant in the lungs
- increased placental oestrogen production

this
- upregulates oxytocin receptors in uterus (so uterus more sensitive to contractions)
- release of oxytocin and prostaglandis ( more sensitive to myometrium contractions and inflammatory response from oestrogen)

this causes myometrial contractions
- this works in a positive contraction loop which causes more contractions

Question 9

How does lactation occur

Answer 9

• milk synthesis from prolactin occurs at mature alveoli
• breast growth stimulated by placental oestrogen, progesterone and hPL
• ## prolactin is released from anterior pituitary gland (inhibited by dopamine/prolactin inhibiting hormone)

Question 10

What is the milk ejection reflex/let down reflex

Answer 10

• suckling stimulates AFFERENT nerves to HYPOTHALAMUS which stimulates OXYTOCIN release from POSTERIOR PITUITARY GLAND
• PROLACTIN release from ANTERIOUR PITUITARY GLAND also stimulated
• OXYTOCIN blinds to receptors on MYOEPITHELIAL CELLS causing milk ejection

dopaminergic neurons causes dopamine to be inhibited which causes more prolactin to be released