Physiology of pregnancy & lactation Flashcards by Sophie McEntegart

Describe what happens to the inner and outer cells of the blastocyst once attached to uterine lining.

inner cells develop into embryo

outer cells burrow uterine wall and become placenta

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Describe implantation of the blastocyst.

Free-floating blastocyst adheres to endometrial lining, cords of trophoblastic cells penetrate the endometrium.
Advancing cords of trophoblastic cells tunnel deeper into endometrium, carving hole for blastocyst.
Implantation finishes on day 12 with blastocyst completely buried in endometrium.

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What is the placenta derived from?

trophoblast and decidual tissue

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What is the name for the multinucleate cells that trophoblast cells differentiate into?

syncytiotrophoblasts

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What is the function of the multinucleate cells which are derived from trophoblast cells ?

invade decidua and breakdown capillaries to form cavities filled with maternal blood

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What does each placenta villi contain?

foetal capillaries separated from maternal blood by a thin layer of tissue.

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By which week of pregnancy are the placenta and foetal heart functional?

5th week

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What is the effect of progesterone signalling the decidual cells?

stimulates decidual cells to concentrate glycogen, proteins and lipids

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Circulation within which space acts partly as an arteriovenous shunt?

intervillous space (thin layer of separation between mother’s blood and foetal blood)

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In relation to the respiratory function of the placenta, maternal blood is oxygen rich and umbilical blood is oxygen-poor.
T/F?

TRUE

Oxygen diffuses from the maternal into foetal circulation system (PO2 maternal > PO2 foetal)

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What kind of gradient does CO2 follow in placental respiratory function?

reversed gradient

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In relation to placental respiratory function, via which vessels does oxygen saturated foetal blood, and oxygen-poor maternal blood return to both?

foetal oxygen saturated blood returns to foetus via umbilical vein
maternal oxygen-poor blood returns to her via uterine veins

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Which 3 factors allow sufficient oxygenation of the foetus to occur?

Foetal Hb
Higher Hb concentration in foetal blood
Bohr effect

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What is the Bohr effect and how does it apply to foetal oxygenation?

Increases in the partial pressure of CO2 in blood or decreases in blood pH -> lower affinity of Hb for O2
(in areas of high CO2, haemoglobin dissociates its O2 to oxygenate the area)
pCO2 is elevated in foetal blood meaning that O2 offloading is in optimum conditions

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How does water enter the placenta? Does its movement change during pregnancy?

diffuses into placenta along its osmotic gradient

exchange increases during pregnancy up to 35th week

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How do electrolytes cross placenta? Are there any exceptions?

follow H2O - iron and calcium go from mother to child directly

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How does glucose pass the placenta?

simplified transport - foetus’ main source of energy

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Fatty acids don’t cross the placenta.

T/F?

FALSE

there is free diffusion of fatty acids across the placenta

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Main role of HCG?

prevents involution of corpus luteum

role in development of sex organs in testes of male foetus

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Which pregnancy hormone is produced from week 5 onwards and has growth hormone-like effects?

human placental lactogen AKA. human chorionic somatomammotropin (HCS)

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What effects do HCS hormone have?

Growth-hormone-like effects: protein tissue formation
Decrease insulin sensitivity in mother - more glucose for foetus
Involved in breast development

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This pregnancy hormone decreases uterus contractility, prepares the breasts for lactation and is involved in the development of decidual cells.

progesterone

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Which hormone enlarges the breasts, uterus and relaxes pelvic ligaments?

oestrogen

What can you diagnose from monitoring HCG levels?

ectopic pregnancy
failing pregnancy
ongoing viable pregnancy

If a pregnancy was ectopic, what would you expect to see on HCG monitoring?

static or slow rising HCG

Falling HCG is a sign of?

failing pregnancy

HCG levels doubling is a sign of?

ongoing viable pregnancy

When might you see high levels of HCG?

multiple pregnancy | molar pregnancy

HCG levels double every 48hrs in a singleton pregnancy and continue to do so until the birth. T/F?

FALSE | serum levels double every 48hrs in a singleton early pregnancy BUT levels fall from 12-14 weeks

List some normal cardiovascular changes seen on investigation?

ECG changes functional murmurs heart sounds

what is the impact on cardiac output of pregnancy?

30-50% above normal from week 6-24 decreases again in last 8 weeks due to uterus compressing vena cava increases 30% more during labour

What happens to heart rate and blood pressure during pregnancy?

HR increases up to 90/min to increase CO | BP drops in 2nd trimester

Describe haematology changes seen in pregnancy.

plasma volume increases proportionately with cardiac output erythropoiesis (RBC) increases Hb is decreased by dilution

How much does iron requirement increase during pregnancy?

6-7mg/day in 2nd half of pregnancy

What causes respiratory changes in pregnancy?

Progesterone increases - signals brain to lower CO2 levels (increases CO2 sensitivity in respiratory centres) Enlarging uterus elevates diaphragm and reduces residual volume / functional residual capacity. Increased metabolic need of mother, foetus & placenta - increases O2 consumption

How are CO2 levels lowered in pregnancy?

increased respiratory rate increased tidal and minute volume by 50% decreased pCO2 slightly (no change in vital capacity and PO2)

Which postural changes increase renal function?

supine position | lateral position during sleep (more so)

Which postural changes decrease renal function?

upright position

What is pre-eclampsia?

pregnancy induced hypertension + proteinuria

What factors contribute to development of pre-eclampsia?

increasing BP since 20th week | Renal function declines - salt & water retention - oedema

What is the single most significant risk factor for developing pre-eclampsia?

previous pre-eclampsia

What is eclampsia?

extreme pre-eclampsia (lethal without treatment)

What are some signs of eclampsia?

vascular spasms, extreme hypertension, chronic seizures & coma

Treatment for eclampsia?

vasodilators and caesarean section

At the end of pregnancy, how much glucose if needed by the foetus?

5mg/kg/min | mum needs half that

Which phase of pregnancy is anabolic and what does this mean for the mother?

``` 1st phase - week 1-20 lower plasma glucose normal/increased insulin sensitivity lipogenesis, glycogen stores increase growth of breasts, uterus & weight gain ```

Which phase of pregnancy is catabolic and what does this mean for the mother?

``` week 21-40 accelerated starvation of mother maternal insulin resistance increased transport of nutrients through placental membrane lipolysis ```

Which hormones cause insulin resistance in mothers?

human placental lactogen (HPL), cortisol and GH

During the onset of labour, what causes intense abdominal muscle contractions?

strong uterine contraction + pain from birth canal -> neurogenic reflexes from spinal cord

What is Fergusons reflex?

+ve feedback mechanism involving oxytocin: oxytocin stimulates uterus to contract & placenta to make prostaglandins; prostaglandins stimulate more vigorous contractions; prostaglandins +ve feedback on their own production & on oxytocin release from pituitary gland

Describe the 1st stage of labour (latent phase)

up to 3-4cms dilation mild irregular uterine contractions cervix shortens and softens

Describe the 1st stage of labour (active phase).

4-10cms (full dilatation) slow descent of presenting part contractions progressively more rhythmic and stronger

Describe 2nd stage of labour.

full dilatation - delivery of baby Prolonged in 1st time births when >3hrs with analgesia or 2 without. Prolonged in multiparous if >2 with analgesia and >1 without.

Describe 3rd stage of labour.

delivery of baby and expulsion of placenta. average duration 10mins should have spontaneous delivery of placenta but can actively manage if not happening.

How are hormones involved in lactation?

oestrogen - growth of ductile system & increase in adipose tissue. progesterone - development of lobule-alveolar system. Prolactin stimulates milk production

What does prolactin stimulate in regards to lactation?

1-7 days after birth, PRL induces high milk production ( in lobules) - stimulates colostrum (low volume, no fat)

Describe the "milk let-down" reflex.

Suckling stimulus causes secretion of oxytocin from pituitary which causes smooth muscle contraction. Suckling also inhibits the release of prolactin inhibiting hormone - releasing prolactin which causes milk secretion