Physiological changes in pregnancy Flashcards
Describe the physiological changes of the respiratory system in pregnancy?
reduced expiratory reserve volume due to diaphragm pushed up in pregnancy and ribs in. Gives a sensation of breathlessness
tidal volume increased (thought to be due to progesterone)
respiratory rate stays the same
residual volume and vital capacity both increase
why is there a state of respiratory alkalosis in mother?
Maternal blood has a low CO2 in order to allow a gradient between maternal and fetal blood to remove fetal CO2.
this is compensated partially by lower HCO3 from renals
pH remains within normal limits.
PO2 is also normal.
What are the physiological changes of cardiovascular system in pregnancy?
progesterone causes vasodilation which results in reduced reduced vascular resistance. This is then accounted for by increased CO. later in pregnancy blood pressure goes back to normal but CO still stays raised.
reduction in BP activates RAS, Na and fluid retention - increased blood volume and dilutional anaemia
vasoconstriction peripherally - raynauds
sometimes ejection systolic murmurs and 3rd heart sounds.
increased risk of:
- varicose veins
- DVT / VTE - due to hypercoaguable state
what are the physiological changes of the urinary system in pregnancy?
increased size of kindeys and increased blood flow and thus eGFR increases.
increase in eGFR means:
- reduced creatinine and urea
- glycosuria (PCT reabsorption rate cant keep up)
- increased frequency of urination
- proteinuria
- loss of bicarbonate
progesterone relaxes smooth muscle of ureters - urinary stasis
why are UTIs more common in pregnancy?
glycosuria (increased GFR) urinary stasis (due to progesterone relaxing ureter and bladder muscle)
asymptomatic bacteriuria should be treated.
what are the dermatological changes seen in pregnancy?
palmar erythema and spider naevus - due to oestrogen
increased MSH results in hyperpigmented nipples and linea nigra
what are the MSK changes seen in pregnancy?
back ache is common
progesterone relaxes and stretches ligaments to allow pelvic outlet to widen for labour
what are the GI changes in pregnancy?
N+V
reflux - due to relaxed oesophageal sphincter (progesterone) and upward displacement of stomach by uterus
constipation - due to relaxed muscles (progesterone)
How does immunity change in pregnancy?
increased risk of infection
why are pregnant women at increased risk of metabolic acidosis?
reduced bicarbonate
ketones produced due to excess lipolysis - this provides free fatty acids for mother so energy is preserved for fetus
which hormones are altered during pregnancy?
increased: Oestrogen, progesterone, prolactin, hCG (human chorionic gonadotrophin), hPL (human placental lactogen), increased T3/4, increased cortisol
Decreased LH, FSH, GH
(note T3/4 are increased but so is TBG and thus overall free levels remain stable)
what are the anti-insulin hormones that act in pregnancy?
prolactin
human placental lactogen
oestrogen and progesterone
cortisol
increases blood glucose levels so more available for fetus.
what are the haematological changes seen in pregnancy?
increased fibrinogen and clotting factors and reduced fibrinolysis i.e hypercoaguable state.
this alongside vasodilation and stasis increases clotting risk.
cant give warfarin only LMWH to those at increased risk
How to recognise signs of pregnancy?
bloating cramping spotting moodiness and fatigue N+V, change in appeptite increased urination frequency larger tender breast
why are the following increased in pregnancy:
- T3/4
- hCG
- hPL
- prolactin
hCG has similar structure to TSH and thus can stimulate the release of T3/4. Thyroxine is really important for fetal brain development. (increased metabolism in pregnancy)
hCG is produced by placenta as soon as conception occurs and is used to maintain corpus luteum until placenta is ready to produce adequate progesterone
human placental lactogen acts as an anti-insulin hormone, ensures adequate glucose in circulation for fetus. also works in similar way to prolactin
prolactin: During pregnancy it is important for water regulation across fetus. after pregnancy it is important in lactation
what cells produce hCG and hPL?
synctiotrophoblasts of placenta.
describe the development of the placenta
At the stage where the blastocyst implants
- blastocyst consists of outer trophoblasts and inner cell mass.
- the outer trophoblasts form the placenta
on day 6 the zona pellucida disintegrates and blastocyst hatches allowing implantation to take place.
trophoblasts interact with the endometrial deducial epithelium to invade uterine wall.
on day 8 the trophoblasts differentiate into synctiotrophoblasts (outer) and cytotrophoblasts (inner)
cytotrophoblasts invade the maternal vessels to remodel them and reduce vascular resistance of spiral arteries.
explain how the mammary glands develop during pregnancy?
mammary glands consist of lobules connected by fibrous tissue. lobules are made of alveoli, blood vessels and lactiferous ducts.
during pregnancy there is significant hypertrophy of ductular- lobular - alveolar system.
high P:O ratio favours growth over milk production.
what happens to the mammary glands soon after birth?
soon after birth the breasts produce colostrum
this is due to drop in progesterone and thus alveoli respond to prolactin to begin milk production
how does colostrum compare to mature milk?
colostrum - water, lactose, fat, protein, vitamins and minerals.
higher protein and fat soluble vitamins
less water soluble vitamins, fat and sugar than mature milk
what is the milk let down reflex?
stimulus e.g. crying or suckling results in oxytocin release which leads to contraction of myoepithelial cells and milk ejection
what is the neuroendocrine reflex for milk production?
suckling results in afferent fibres to hypothalamus which inhibit dopamine release and thus promote more prolactin release which stimulates breasts to produce more milk.
when is normal delivery expected?
between weeks 38 and 41
occurs within 24 hours of onset of regular contractions
What are Braxton hicks contractions?
From T1 the uterus undergoes physiological contractions (to practice)
these become more regular by >36 weeks
during labour the pressure produced by these contractions increases.
how many stages of labour are there?
3
How is stage 1 of labour defined?
stage 1 is defined by fully effaced cervix (flattening of bulb of cervix) and dilation to at least 3 cm and there are regular contractions
What happens during stage 1 of labour?
the cervix continues to dilate and reaches full dilation within 7 to 12 hours (this is now stage 2 of labour)
what checks should be made during stage 1 of labour?
vaginal examination to check position of head and dilation of cervix - every 4 hours
maternal urine - every 4 hours - to check for protein and ketones.
maternal temperature and BP every 1/2 hour
contractions and fetal HR every 15 mins
what defines stage 2 of labour?
cervix is fully dilated to delivery of the fetus
what occurs in stage 2 of labour ?
Contractions continue - mum uses abdominal muscles and Valsalva manoeuvre to push fetus out.
how long does stage 2 of labour take?
primum 45 mins to 120 mins
multi - 15 to 45 mins
describe how a fetus is delivered.
engagement - largest part of fetal head has entered the pelvis
descent and flexion - head flexes towards mothers mum and then descends.
internal rotation of the head and extension
head delivered
head realigns with shoulders
shoulders externally rotate and are delier.
what defines the 3rd stage of labour?
delivery of placenta and membranes
should DVT prophylaxis be given post delivery?
if >35 yrs and >35 BMI and any other risk factors
or 2 risk factors
risk factors include: parity >/= 4, varicose veins, paraplegia, sickle cell, nephrotic syndrome, previous VTE, cardiac disease, pre-eclampsia, thrombophilia, IBD, myeloproliferative disease, infection, use of foreceps, manual evacuation of products, excess blood loss, post partum sterilisation.
why does eGFR increase in pregnancy?
reduced vascular resistance (due to progesterone) results in increased CO
also the blood volume has increased (due to RAS)
why are renal and biliary stones more common in pregnancy?
stasis of fluid due to dilation by progesterone
what defines T1, T2 and T3?
T1 = week 1 to 12 T2 = week 13 to 28 T3 = week 29 to 41
