Physiological changes in pregnancy

Question 1

Describe the physiological changes of the respiratory system in pregnancy?

Answer 1

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

Question 2

why is there a state of respiratory alkalosis in mother?

Answer 2

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.

Question 3

What are the physiological changes of cardiovascular system in pregnancy?

Answer 3

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

Question 4

what are the physiological changes of the urinary system in pregnancy?

Answer 4

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

Question 5

why are UTIs more common in pregnancy?

Answer 5

glycosuria (increased GFR)
urinary stasis (due to progesterone relaxing ureter and bladder muscle) 

asymptomatic bacteriuria should be treated.

Question 6

what are the dermatological changes seen in pregnancy?

Answer 6

palmar erythema and spider naevus - due to oestrogen

increased MSH results in hyperpigmented nipples and linea nigra

Question 7

what are the MSK changes seen in pregnancy?

Answer 7

back ache is common

progesterone relaxes and stretches ligaments to allow pelvic outlet to widen for labour

Question 8

what are the GI changes in pregnancy?

Answer 8

N+V
reflux - due to relaxed oesophageal sphincter (progesterone) and upward displacement of stomach by uterus
constipation - due to relaxed muscles (progesterone)

Question 9

How does immunity change in pregnancy?

Answer 9

increased risk of infection

Question 10

why are pregnant women at increased risk of metabolic acidosis?

Answer 10

reduced bicarbonate

ketones produced due to excess lipolysis - this provides free fatty acids for mother so energy is preserved for fetus

Question 11

which hormones are altered during pregnancy?

Answer 11

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)

Question 12

what are the anti-insulin hormones that act in pregnancy?

Answer 12

prolactin
human placental lactogen
oestrogen and progesterone
cortisol

increases blood glucose levels so more available for fetus.

Question 13

what are the haematological changes seen in pregnancy?

Answer 13

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

Question 14

How to recognise signs of pregnancy?

Answer 14

bloating
cramping
spotting 
moodiness and fatigue
N+V, change in appeptite
increased urination frequency 
larger tender breast

Question 15

why are the following increased in pregnancy:

• T3/4
• hCG
• hPL
• prolactin

Answer 15

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

Question 16

what cells produce hCG and hPL?

Answer 16

synctiotrophoblasts of placenta.

Question 17

describe the development of the placenta

Answer 17

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.

Question 18

explain how the mammary glands develop during pregnancy?

Answer 18

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.

Question 19

what happens to the mammary glands soon after birth?

Answer 19

soon after birth the breasts produce colostrum

this is due to drop in progesterone and thus alveoli respond to prolactin to begin milk production

Question 20

how does colostrum compare to mature milk?

Answer 20

colostrum - water, lactose, fat, protein, vitamins and minerals.
higher protein and fat soluble vitamins
less water soluble vitamins, fat and sugar than mature milk

Question 21

what is the milk let down reflex?

Answer 21

stimulus e.g. crying or suckling results in oxytocin release which leads to contraction of myoepithelial cells and milk ejection

Question 22

what is the neuroendocrine reflex for milk production?

Answer 22

suckling results in afferent fibres to hypothalamus which inhibit dopamine release and thus promote more prolactin release which stimulates breasts to produce more milk.

Question 23

when is normal delivery expected?

Answer 23

between weeks 38 and 41

occurs within 24 hours of onset of regular contractions

Question 24

What are Braxton hicks contractions?

Answer 24

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.

Question 25

how many stages of labour are there?

Answer 25

3

Question 26

How is stage 1 of labour defined?

Answer 26

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

Question 27

What happens during stage 1 of labour?

Answer 27

the cervix continues to dilate and reaches full dilation within 7 to 12 hours (this is now stage 2 of labour)

Question 28

what checks should be made during stage 1 of labour?

Answer 28

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

Question 29

what defines stage 2 of labour?

Answer 29

cervix is fully dilated to delivery of the fetus

Question 30

what occurs in stage 2 of labour ?

Answer 30

Contractions continue - mum uses abdominal muscles and Valsalva manoeuvre to push fetus out.

Question 31

how long does stage 2 of labour take?

Answer 31

primum 45 mins to 120 mins

multi - 15 to 45 mins

Question 32

describe how a fetus is delivered.

Answer 32

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.

Question 33

what defines the 3rd stage of labour?

Answer 33

delivery of placenta and membranes

Question 34

should DVT prophylaxis be given post delivery?

Answer 34

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.

Question 35

why does eGFR increase in pregnancy?

Answer 35

reduced vascular resistance (due to progesterone) results in increased CO
also the blood volume has increased (due to RAS)

Question 36

why are renal and biliary stones more common in pregnancy?

Answer 36

stasis of fluid due to dilation by progesterone

Question 37

what defines T1, T2 and T3?

Answer 37

T1 = week 1 to 12
T2 = week 13 to 28 
T3 = week 29 to 41