Physiology of pregnancy and lactation Flashcards
Describe the changes seen as the ovum progresses from the ampulla to implantation?
Polar bodies form
Cleavage
Morula formed
Blastocyst
What is the difference between the inner cell mass and trophoblast?
Inner cell mass; destined to become foetus
Trophoblast; accomplishes implantation and develops into foetal portions of placenta
What occurs day 3-8 in fertilisation?
3-5; transport of blastocyst into uterus
5-8; blastocyst attaches to lining of uterus
How does the blastocyst implant on the endometrial wall?
When the free-floating blastocyst adheres to endometrial lining, cords of trophoblastic cells begin to penetrate the endometrium
Advancing cord of trophoblastic cells tunnel deeper into endometrium, carving out a hole for the blastocyst.
Boundaries between cells in advancing trophoblastic tissue disintegrate
When is the implantation completed?
Day 12
From what cells is the placental derived from?
Trophoblast
Decidual
What will trophoblast cells differentiate into?
Multinucleate cells (syncytiotrophoblasts) which invade the decidua and break down capillaries to form cavities filled with maternal blood
How does the placenta get a vascular supply?
Developing embryo sends capillaries into the syncytiotrophoblast projections to form placental villi
What does each villus contain?
Foetal capillaries separated from maternal blood by a thin layer of tissue
When is the placental and foetal heart functional?
Week 5
How does the embryo gain nutrition from the placenta?
Invasion of trophoblastic cells into the decidua
What will hCG stimulate?
Corpus luteum to continue to secrete progesterone
What is the function of progesterone in early pregnancy?
Stimulates decidual cells to concentrate glycogen, proteins and lipids
What occurs in terms of vasculature as the placenta develops?
It extends hair like projections into the uterine wall
Increasing contact area between uterus and placenta allowing for more nutrients to be exchanged
Where do blood vessels from the embryo develop?
In villi
A thin membrane separates the embryo’s blood in villi from mother’s blood in the intervillous space
Is there direct contact between maternal and foetal blood?
No; circulation within intervillous space acts partly as an arteriovenous shunt
What is the role of the placenta in oxygen transport?
Plays the role of foetal lungs
Supplies oxygen, removes carbon dioxide
How does maternal oxygen diffuse into foetal circulation?
The partial pressure of oxygen in mother is higher that foetus
How can carbon dioxide be removed from foetus?
Partial pressure is elevated in foetal blood to allow for a reversed gradient
Through which structure is foetal oxygenated blood returned to the foetus?
Umbilical vein
Through which structure is maternal oxygen poor blood returned?
Uterine vein
What 3 factors facilitate foetal oxygen supply?
Foetal Hb; increased ability to carry oxygen
Higher Hb; concentration in foetal blood is more than 50% of adults
Bohr effects; foetal Hb can carry more oxygen in low pCO2 than in high pCO2
What is the function of hCG?
Prevents involution of corpus luteum (stimulates progesterone, oestrogen)
Effect on testes of male foetus; development of sex organs
When is hPL produced?
Week 5 of pregnancy
What is the function of hPL?
Growth hormone like effect; protein tissue formation
Decreases insulin sensitivity in mother; more glucose for foetus
Involved in breast development
Which hormones are responsible for the development of gestational diabetes in women?
Human placental Lactogen
Cortisol
Growth hormone
What is the function of progesterone in pregnancy?
Development of decidual cells
Decreases uterine contractility
Preparation for lactation
What is the function of oestrogen in pregnancy?
Enlargement of uterus
Breast development
Relaxation of ligaments
What should happen to hCG levels in pregnancy?
Should double every 48 hours in a singleton early pregnancy
For what conditions can hCG be used to diagnose/ monitor?
Ectopic; static or slow rising
Failing pregnancy; falling
Ongoing viable pregnancy; doubling or > 60% rise
What are the side effects of rising hCG in pregnancy?
Nausea
Vomiting
HYPEREMESIS GRAVIDARUM
When are high levels of hCG common?
Multiple pregnancy
Molar pregnancy
When should hCG levels peak and fall?
Peak; 8-12 weeks
Fall from 12-14 weeks then plateau
What is the role of CRH in pregnancy?
Increased ACTH
Increased aldosterone and cortisol
Hypertension and oedema + insulin resistance
What is the sequelae of increased hCG in pregnancy?
Hyperemesis gravidarum
Hyperthyroidism
What is the sequelae of increased calcium demands in pregnancy/?
Hyperparathyroidism
Does CO change in pregnancy?
Increased due to demands of uteroplacental circulation
How will CO change as the pregnancy progresses?
30-50% above normal from 6-24wks
Decreases in last 8 weeks
Increases by 30% in labour
What is the resultant effect of increased CO in pregnancy?
Placental circulation
Increased metabolism
Skin; thermoregulation
Renal circulation
Will HR increase in pregnancy?
Yes; up to 90/min to increase CO
What occurs with BP in pregnancy?
Drops during 2nd trim (uteroplacental circulation expands and peripheral resistance decreases)
With multiple pregnancies, CO increases more, BP drops more
What are the haematological changes assoc with pregnancy?
Plasma volume increases proportionally with CO
Erythropoiesis increases by 25%
Hb is decreased by dilution (decreasing blood viscosity)
Iron requirements increase (6-7mg/day in 2nd trim)
Which hormone results in the resp changes seen in pregnancy?
Progesterone increases and enlarging uterus
What is the role of progesterone in resp changes in pregnancy?
Signals brain to lower co2 levels (increases co2 sensitivity in resp centres )
What are the 3 factors that change respiration in pregnancy?
Progesterone action on brainstem
O2 consumption increases (20% above normal)
Growing uterus
What are the mechanisms the body will adapt to lower co2 levels in pregnancy?
RR increases
Tidal and minute volume increases (50%)
pCO2 decreases slightly
Vital capacity and pO2 don’t change
Will GFR and renal plasma flow increase in pregnancy?
Yes; both increase up to 30-50% with a peak at 16-24 weeks
What is the resultant effect of increased GFR and renal plasma flow in pregnancy?
Increased re-absorption of ions and water
Placental steroids
Aldosterone
Increased urine formation
What effect does posture have on renal function in pregnancy?
Upright position; decreased
Supine; increased
Lateral position in sleep; increased alot
What is preeclampsia?
Pregnancy induced hypertension and proteinuria
At what week can preeclampsia be diagnosed?
20th week
What happens to renal function in pre-eclampsia?
Declines; salt and water retention (oedema esp hands and face)
Renal blood flow and GFR decrease
What are risk factors for pre-eclampsia?
Pre-existing hypertx Diabetes Autoimmune disease (lupus) Renal disease Family history of preeclampsia Obesity Women with multiple gestation
What is the single most significant risk for preeclampsia?
Previous pre-eclampsia
What causes pre-eclampsia?
Extensive secretion of placental hormones
Immune response to foetus
Insufficient blood supply to placenta; ischaemia
What is eclampsia?
Extreme pre-eclampsia which is lethal without treatment
What are the symptoms of eclampsia?
Vascular spasm
Extreme hypertension
Chronic seizures
Coma
What is the treatment for eclampsia?
Vasodilators
C-section
What is the average maternal weight gain in pregnancy?
11kg; but can be as much as 30kg
What makes up the maternal weight gain?
Foetus; 3.5kg Extra-embryonic fluid/ tissue; 2 kg Uterus; 1kg Breast; 1kg Body fluid; 2.5kg Fat accumulation; 1kg
How should the diet of a mother change whilst pregnant?
200 kcal - 85% foteal metabolism, 15% stored as maternal fat
30g/day protein
End of pregnancy; foetal glucose needs 5mg/kg/min therefore mother requires 2.5mg/kg/min
What is the 1st phase of pregnancy?
Weeks 1-20; mothers anabolic phase
Anabolic metabolism of mother
Small nutritional demands of conceptus
What is the 2nd phase of pregnancy?
21-40 weeks esp last trim
High metabolic demands of foetus
Accelerated starvation of mother
What occurs in the mothers anabolic phase?
Normal or increased sensitivity to insulin
Lower plasmatic glucose level
Lipogenesis, glycogen stores increased
Growth of breasts, uterus, weight gain
What occurs in the mothers catabolic phase?
Maternal insulin resistance
Increased transport of nutrients through placental membrane
Lipolysis
What are the special nutritional needs in pregnancy?
Folic acid; reduces risk of neural tube defects Vit d; esp in overweight women High protein diet; higher energy uptake Iron supplements B vits - erythropoiesis
What hormone ratio changes resulting in increased excitability of uterus?
Oestrogen: prog
Progesterone inhibits contractility whilst oestrogen increases
What is the role of oxytocin in parturition?
Increases contraction and excitability
What hormones does the foetus produce?
Oxytocin
Adrenal gland
Prostaglandins
What stimulates uterine contraction?
Mechanical stretch of uterine muscles
Stretch of cervix - oxytocin release
When will women get braxton Hicks contractions?
Near end of pregnancy
What acts as a positive feedback mechanism in the onset of labour?
Stretch of cervix by foetal head increases contractility
What impact will strong uterine contraction have on the spinal cord?
Neurogenic reflexes that will induce intense abdominal muscle contractions
What is the effect of oestrogen on initiation of labour?
Induces oxytocin receptors on the uterus
What is the effect of oxytocin in initiation of labour?
Stimulates uterus to contact
Stimulates placenta to make prostaglandins
What is the effect of prostaglandins on initiation of labour?
Stimulates more vigorous contractions of the uterus
What is the 1st stage of labour?
Cervical dilation (8-24 hours)
What is the 2nd stage of labour?
Passage through birth canal (few mins to 120 mins)
What is the 3rd stage of labour?
Expulsion of placenta
What effect does oestrogen have on the production and release of milk?
Growth of ductile system
What effect does progesterone have on the production and release of milk?
Development of lobule-alveolar system
What effect does E and P have on milk production?
Inhibit
At birth; sudden drop in E and P
Oestrogen = growth of ductile system
Progesterone = growth of lobules
What effect does prolactin have on the production and release of milk?
Stimulates milk production (steady rise in levels from wk 5 to birth)
1-7 days after birth, prolactin induces high milk production
Stimulates colostrum
What are the components of colostrum?
High protein
High immunoglobulin allowing for foetal immunity
Which hormones are involved in the milk let down reflex?
Oxytocin
Prolactin
