maternal adaptations to pregnancy

Question 1

what facilitates maternal adaptations?

Answer 1

Two-way communication between maternal and fetal tissues

pregnancy hormones

• placental hormones (steroid hormones - oestrogen/progesterone, protein hormones (HCG, HPL, CRH prolactin, oxytocin, relaxin, POMC, placental GH & ALP, human chorionic thyrotropin & ACTH, activin, inhibin, pregnancy specific B1 glycoprotein)
• subsequent effects on maternal endocrinology

Question 2

what is HCG produced by and what are its functions?

Answer 2

produced by synctiotrophoblast
Marked rise first trimester then declines
Signals presence of blastocyst to mother
Maintainscorpus luteum

Question 3

what are progestins produced by and the what are their roles?

Answer 3

produced by the corpus lute and then the placenta
Increases until just before labour
“Pro-gestational”……
- Smooth muscle relaxation (many effects, including peripheral vasodilation)
- Inhibits OTR expression
Increases maternal ventilation
Promotes glucose deposition in fat stores
Raises body temperature

Question 4

what is the role of oestrogen and what are they produced by?

Answer 4

oestrogen are produced by the corpus lute and then the placenta

they increase just before labour 
Promotes changed in CV system 
alter carbohydrate metabolism - insulin resistance 
breast, nipple growth 
uterine blood flow, myometrial growth 
cervical softening 
increases oxytocin receptors in myometrium 
water retention 
thyroid mining globulin

Question 5

what is the is the role of hPL/human chorionic sommatomammotropin? what is it produced by?

Answer 5

produced by syncytiotrophoblast
Increases throughout pregnancy, levels proportional to size of placenta
Lactogenic and stimulates growth
Converts mammary glands into milk-secreting tissue
Mobilises glucose from fat reserves
↑insulin secretion but
↓insulin’s peripheral effect (fatty acids and glucose diverted to the fetus)

Question 6

what is the role of placental CRH?

Answer 6

Increases throughout pregnancy, overall CRH levels rise over 1000 fold.

Plays a role in timing of parturition, interacts with maternal and fetal HPA systems.

Question 7

what is the role of prolactin and what is it produced by?

Answer 7

produced by anterior pituitary
Milk production (but ONLY when E and P have declined post-partum)
Increases throughout pregnancy - levels 10-20 x higher by term.

Question 8

what is oxytocin produced by and what are its actions

Answer 8

posterior pituitary and placenta
Acts on uterus and breasts
Contraction of smooth muscle of uterus and PG production
Milk Ejection Reflex

Question 9

what is relaxin produced by and what are its actions?

Answer 9

produced by CL, decidua and placenta

Secreted by corpus luteum, decidua and placenta

Facilitates remodelling of connective tissue of reproductive tract in preparation for labour.

Question 10

why do physiological changes happen during pregnancy?

Answer 10

supply nutrients to the foetus
support amniotic fluid production
clear fetal waste products.
meet fetal and placental demands for glucose, amino acids and oxygen
adapt in preparation for labour - protect mum from CV insults at time of delivery

Question 11

what happens during each menstrual cycle to rehearse pregnancy?

Answer 11

peripheral vasodilation and resultant haemodynamic changes occur occur during each luteal phase

Question 12

what maintains pregnancy until placenta is formed?

Answer 12

Blastocyst HCG secretion prevents luteal regression

Corpus luteum synthesizes progestins until placenta is formed  Placenta takes over E and P production from ~9/40

Question 13

what are anatomical adapations of the uterus during pregnancy?

Answer 13

• 10 fold increase in weight and blood flow
• size: pear shaped organ around 10ml volume –> 5000ml volume
  composition: muscle cell hypertrophy, increased elastic tissue, increased supportive fibrous tissue
  mainly hypertrophy/hyperplasia in first half of pregnancy, then stretch effect
  hypertrophy of uterine and ovarian vessels
  orientation:straightens and dexrotates with increase in size

Question 14

what are the anatomical adaptations to the cervix during pregnancy?

Answer 14

increased vascularity and oedema, softening
increase In cervical glands –>production of tenacious mucous plug
hyperplasia/eversion of endo-cervical epithelium

Question 15

what are anatomical adaptations to the vagina during pregnancy?

Answer 15

• venous congestion –> blu/purple tinti(affects cervix too)
  oestrogen –> increased glycogen deposition in epithelium –> increased lactic acid (protective)

Question 16

what are the anatomical adaptations of the breasts during pregnancy?

Answer 16

lactiferous ducts and alveoli proliferate –> increase in size (cause by oestrogen and progesterone_
skin changes
colostrum produced
lactation (sudden drop in oestrogen and progesterone and increase in prolactin –> lactation)
suckling –> increased oxytocin –> milk ejection.

Question 17

what systems are affected during pregnancy?

Answer 17

CV
resp
haematological/coagulation 
renal 
GI
endocrine/metabolic 
immunological

Question 18

what are CV adaptations during pregnancy?

Answer 18

HR - increases, up to 20% by 3rd trimester
SV increases
CO - increases very early in 1st trimester, plateaus, increases again at start of labour
TRP/SVR - falls
BP - falls until 24/40 then slowly recovers to normal values at term
plasma volume increases

Question 19

what causes increase CO during pregnancy?

Answer 19

increased HR
decreased HR variability
Increased stroke volume

BP falls despite the increase in CO because of the marked fall in peripheral resistance

Question 20

what does lowered total peripheral resistance lead to in pregnancy?

Answer 20

decreased after load –> perceived underselling –> activation of RAAS –> increased plasma volume >50% (and reduced plasma osmolality)

Question 21

what is aortocaval compression?

Answer 21

From 20/40 gravid uterus is big enough to compress great vessels.
Supine position at term -> 30-50% reduction in CO.
May be asymptomatic or cause marked hypotension.
Reduces uteroplacental perfusion -> fetal distres

Question 22

what is the uterine blood flow at term?

Answer 22

500-800ml/minute
◦ Blood loss can accumulate rapidly in postpartum haemorrhage
◦ Circulating volume only ~5000ml – identify & treat promptly!

Question 23

what are the respiratory adaptations during pregnancy?

Answer 23

overall, less demand on respiratory than CV system
Patients with lung disease do relatively well in pregnancy unless severely affected

mechanism for changes
- increased oxygen consumption (around 16%) and Carbon dioxide production –> increase in tidal volume –> increase in ventilation –> decrease in pCO2
trigger unclear
progesterone possibly lowers threshold/increases sensitivity of respiratory centre to CO2

Tidal volume - increases 
Total lung capacity - decreases 
Vital capacity - non change 
inspiratory capacity - increases
expiratory reserve volume - decreased
residual volum - decreased 
functional residual capacity - decreased 
RR - no change

Question 24

what are the mechanical changes in pregnancy?

Answer 24

uterus expands
Lower ribs flare (ligaments relax - hormonal effect)
diameter of chest increases

the diaphragm is raised by 5cm
chest wall compliance decreases

Question 25

what facilitates efficient gas change in the foetus?

Answer 25

maternal pCO2 reduced to less than half of fetal pCO2

Question 26

what are the haematological adaptations during pregnancy ?

Answer 26

blood volume expand around 45%
fluide redistribution: increased plasma and interstitial volume

red cell mass increases ( number and size) due to increased erythropeisis
Iron requirements go up

plasma volume increase is greater than red cell increase –> dilution anaemia of pregnancy
- haemoglobin and haematocrit fall
WCC rises, particularly neutrophils
T and B lymphocyte counts stable but decrease function –> increased susceptibility to some infections

platelet count unchanged

pregnancy is a hyper-coagulable state
pro-coagulation clotting factors increase
inhibitory clotting factors fall

highest risk for thromboembolism in postnatal period
VTE is consistently one of the comments causes of direct maternal death in the UK

Question 27

what are renal adaptations during pregnancy ?

Answer 27

functional and structural adaptations occur - these support CV system adaptation

Structural : increased blood flow (kidneys increase 1cm in length)
increase progesterone (= increase in size of. collecting system)
compression from gravid uterus at pelvic brim –> physiological hydronephrosis (R>L) present in 80% of woman.

overall effect = mild obstruction/urinary stasis = increased infection risk

Functional adaptations:
Renal blood flow(35-60%)
Glomerular filtration rate(40-50%)
◦ Affects urea and creatinine
◦ Affects interpretation of timed urine collection
Glycosuria common in pregnancy (GFR and decreased resorption in distal tubules)

ResistancetoangiotensinIIdevelopsandRAAS generally activated
◦ -> Large increase in extracellular water and Na/H2O retention

Question 28

what are the GI/metabolic adaptions

Answer 28

Progesterone effects:
◦ Relaxed lower oesophageal sphincter
+ pressure from uterus = reflux!
◦ Decreased gastric/intestinal motility
Gall bladder increases in size, empties slower -> degree of cholestasis
Progressive insulin resistance during 2nd
half of pregnancy:  blood glucose, crosses
placenta readily.
◦ ?Due to hPL/cortisol
Lipids increase – can’t interpret bloods in pregnancy.

Question 29

what immunological changes in pregnancy?

Answer 29

Shift from TH1 to TH2 immunological response
◦ Tolerance of fetus
◦ Susceptibility to infection
Influenza
◦ Amelioration of some TH1 mediated conditions e.g
Rheumatoid arthritis

Question 30

what is the intra-partum physiology?

Answer 30

• each contraction expels 300-500ml of blood into circulation
  increases venous return/preload
  increases cardiac output

pain, valsalva, anxiety, and position also affect CO

epidural can stabilise changes in CO (less HR variation ) used early in some cardiac patients

Overall CO increases as labour progresses (15% latent phase, 30% active phase, 45% second stage - pushing, 80% third stage)

Question 31

what are minor symptoms of pregnancy?

Answer 31

 Nausea & vomiting
 Heartburn
 Backache
 Urinary frequency
 Haemorrhoids/constipation
 Leg cramps
 Oedema
 Breast tenderness
 Paraesthesia
 Varicose vein