Physiology of Pregnancy and Lactation Flashcards
At what stage does the embryo implant into the uterus
Blastocyst- inner cells become embryo. Outer cell burrow into uterine wall and become placenta
What is the stage before blastocyst
Morula
When does the blastocyst attach to the lining of the uterus
Day 5-8
What are the surface layer cells of the blastocyst called
trophoblast
By what day does the blastocyst become buried in the uterine lining
day 12
What is the placenta made from
Trophoblast and decidual tissue
When is the placenta and foetal heart functional
by week 5 of the pregnancy
How is the placental developed
Invasion of trophoblastic cells into the decidua
HCG is secreated which signals to the corpus luteum to continue to secret progesterone - this stimulate decidual cells to concentrated glycogenm proteins and lipids to help placental development
How does fetal, oxygenated blood return to the fetus
via the umbilical vein
how does maternal, now oxygen poor blood flow from the intervillous space back to the maternal circulation
via the uterine arteries
What is different about fetal Hb
increased ability to carry oxygen
higher Hb conc in fetal blood
Fetal Hb can carry more oxygen in low PCO2 than high pCO2
What is the function of HCG
prevents involution of the corpus luteum (progesterone production maintained)
effect on testes of mall fetus - helps develop sex organs
What is human chorionic somatomammotropin (HCS)
Growth hormone like effects - protein tissue formation
Decreases insulin sensitivity in the mother - more glucose available for the fetus
Involved in breast development and possibly lactation (?)
When is HCS produced
from week 5
what is the function of progesterone
development of decidual cels
decreases uterus contractility
preparation for lactation
What is the purpose of oestrogens
enlargement of uterus
breast development
relaxation of ligaments
what does the estriol level indicate
the vitality of the fetus
What conditions can result as a consequence of hormonal changes in pregnancy
Hypertension
Diabetes
Hyperthyroidism
Hyperparathyroidism
Why can hypertension and diabetes occur
CRH is increased – ACTH increases – aldosterone increases = HYPERTENSION
Increased ACTH – increased cortisol – insulin resistance and oedema = gestational diabetes.
Why can hyperthyroidism occyr
HCG can causes increase thyroxin
Why can hyperparathyroidism occur
increased calcium demands
how much does the cardiac output increase in pregnancy
30-50 percent beginning week 6 and peaking at wk 24
Why is the CO increased in pregnancy
demands of uteroplacental circulation
increases metabolism
renal circulation
thermoregulation
when does the CO decrease in pregnancy and why is this
the last 8 weeks - the uterus compresses vena cava
but increases again in labour
How are the heart rate and BP affected by pregnancy
Hr- increased up to 90/min
BP- drops during second trimester
What are the haematological changes in pregnancy
Plasma volume increases
Erythropoeiss increased by 1/4
Hv is decreased by dilutsion and this decreases blood viscosity
Iron requirements increase to 6-7mg/day in 2nd half
Why do lung changes occur
Progesterone increase - progesterone signals the brain to lower CO2 levels
enlarging uterus interferes with lung function
O2 consumption increases
How are CO2 levels lowered
increased resp rate
tidal and minute volume increases
PCO2 decreases
no change on PO2 or vital capacity
What changes occur in the urinary system
glomerular filtration rate and renal plasma flow increase up to 30-50 percent
increased reabsorption of ions and water
slight increase in urine formation
why is there more reabsorption of ions and water
because of increased aldosterone
and increased placental steroids
how do postural changes affect renal function
upright position - decreased
supine- increased
lateral position during sleep - very increased
How much weight does a mother typicaly gain
11kgs
5- fetus
6- mother
how many extra calories should be ingested a day in pregnancy
250-300
30g extra protein
When does the fetus have high metabolic demands
wks 21-40
What special nutritional needs are there in pregnancy
high protein diet iron supplements 300mg B vitamins for erythropoesis folic acid vit D3 and calcium supplements vitamin K before parturition
What happens to the oestrogen:progesterone ratio in parturition
Oestrogen increases as it increases contractility while progesterone inhibits it
What other factors increase contractility
Maternal and fetal oxytocin
mechanical stretch of uterine muscle fibres
stretch of the cervix
what does prostaglandidn fo
control timing of labour
What effect does oestrogen and progesterone do in terms of lactation
Oestrogen - growth of ductile system
Progesterone- development of lobule alveolar system
Both inhibit milk production so their levels drop suddenly at birth
What does prolactin do
stimulates milk production
stimulates colostrum
describe the milk let down reflex
receptors in nipples stimulated- impulses propagates to spinal cord- stimulation of hypothalamic nuclei- oxytocin released- contraction- milk ejected
where is oxytocin released from
the posterior pituitary gland
describe the mothers nutritional status throughout pregnancy
wks 1-20 = anabolic
wks 21-40= catabolic ie fetus has high demands, mother experiences accelerated starvation
what happens in the anabolic phase
normal or increases insulin sensitivity
lower plasmatic glucose level
lipogeneis, glycogen stores
growth of breasts, uterus, weight gain
what causes insulin resistance in pregnancy
HCS
cortisol
growth hormone
