Maternal changes Flashcards
How may pregnancy precipitate maternal illness?
- exacerbate a pre-existing condition
- uncover a hidden or mild condition
What are the main changes that occur during pregnancy for the woman?
- increased uterine size
- increased metabolic requirements (of uterus)
- structural and metabolic demand of foetus
- foetal waste removal
- production of amniotic fluid
- preparation of delivery and puerperium
Which hormones mediate the maternal changes during pregnancy?
PLACENTAL PEPTIDES
hCG, hPL, GH
MATERNAL STEROIDS
placenta takes over oestrogen and progesterone production at ~ wk 7
PLACENTAL/FOETAL STEROIDS
progesterone, oestradiol, oestriol
PITUITARY PEPTIDES
GH, thyroid hormones, PL, CRF
What is the general effect of placental steroids during pregnancy?
Profound vasodilation Uterine quiescence (inhibits contraction during pregnancy)
effects on:
- RAAS (increased)
- Respiratory centre (increased RR and minute ventilation)
- GI tract (reduced motility)
- blood vessels
- uterine myometrial contractility
How much weight gain occurs during pregnancy?
TOTAL: 12.5-13kg
failure to gain or sudden change needs to be monitored
What are the maternal differences to energy balance during pregnancy?
INCREASED ENERGY
increased output: respiration and CO
increased storage: for foetus, labour and puerperium
FAT/PROTEIN GAIN (4-5kg)
- increased consumption
- reduced use
- mainly laid down in ANTERIOR ABDO WALL
- utilised in late pregnancy and puerperium
What happens to the BMR during pregnancy?
BMR = basal metabolic rate
INCREASED generally
MID GESTATION: +350kcal/day
LATE GESTATION: +250kcal/day
What occurs to the MATERNAL reserves of glucose during the 1st trimester?
- beta cell hyperplasia
- hyperinsulinaemia
- fasting hypoglycaemia (relative)
laid down as glycogen stores and used by muscle
What occurs to the FOETAL reserves of glucose during the 2nd trimester?
- hPL, E2 and cortisol: INS resistance in mother
(less GLU into stores) - increased glucose available in serum (more crosses placenta)
=> this can cause GDM - INS
How do placental steroids affect the RAAS system during pregnancy?
[E2 and P]
- sodium retention
- osmostat reset
- decreased thirst threshold
- reduced plasma oncotic pressure (hypoalbuminaemia)
What effects does oedema caused by RAAS activation have during pregnancy?
- leakage: swollen ankles
- softening of lungs
- softening of connective tissue ligaments (prepare for labour)
How is maternal respiration affected during pregnancy?
INCREASED O2 CONSUMPTION
- hypercapnia in central respiratory centre
- thoracic anatomy: ribs displaces upwards and flare outwards
- breathing more deeply
- increased minute volume (+40%)
- arterial PO2 increases (+10%)
- arterial PCO2 decreases (-15-20%)
FACILITATES GAS TRANSFER TO FOETUS
What maternal blood changes occur during pregnancy?
- increased maternal blood volume (+40%)
- increased red cell mass (+18%) due to elevated EPO
BUT HAEMODILUTION overall - increased white blood cells and reduced platelets
- oestrogen stimulate clotting factor synthesis from liver
=> HYPERCOAGUBLE blood - increased iron absorption efficiency from gut
How may foetal hypoxia occur in utero?
smoking increases maternal carboxy-Hb
permanent change to Hb
reduced O2 binding capacity
but increased binding of CO to HbF
= foetal hypoxia
What maternal changes in the heart occur during pregnancy?
EXPANDING UTERUS
- left axis deviation of heart
- ECG changes and altered heart sounds
INCREASED CARDIAC OUTPUT
- increased HR and SV
- +40% by 28 weeks (max.)
- CO increase for maternal muscle and foetal supply
Why does the maternal stroke volume increase during pregnancy?
oestrogen/progesterone stimulate RAAS
Aldosterone axis promotes water retention
increased plasma volume
=> INCREASED SV
What maternal changes in the vascular system occur during pregnancy?
REDUCED PERIPHERAL RESISTANCE
- increased CO
- vasodilation
NEOANGIOGENESIS (+ increased flow)
- uterus, placenta, muscle, kidneys and skin
- spider naevi: extra capillaries in skin to assist heat loss
What maternal changes in the GI tract occur during pregnancy?
[Steroid effect]
- increased appetite and thirst
- reduce GI motility (constipation)
- relaxed lower oesophageal sphincter (acid reflux)
What is folate involved in the synthesis of?
- DNA production (S phase)
- global growth
- RBC synthesis
What maternal changes in the urinary system occur during pregnancy?
DILATION+RELAXATION OF URINARY TRACT
increased UTI due to urinary stasis
INCREASED BLOOD FLOW TO KIDNEY
- increased GFR
- increased clearance of creatinine, urea and uric acid
What maternal changes in the uterus occur during pregnancy?
huge increase in muscle mass and blood flow
muscle fibres grow in SPIRAL formation
when they contract, they will push baby out of birth canal
What are the different types of C-section used in delivery?
USCS: upper segment
rare performed in modern medicine
increased risk of bleeding
reduced healing time
LSCS: lower segment
less bleeding
heals better
What maternal changes in the cervix occur during pregnancy?
Main function: retain pregnancy
- increased vascularity
- softening and expansion prep from 8 wks (breakdown and oedema of connective tissue)
- gland proliferation (increased mucosa, mucus and anti-infective functions)
- mucus plug: created by columnar glandular epithelium cells
What processes occur post-delivery to return maternal physiology to normal?
Dramatic and rapid fall in steroids on delivery of the placenta
Most endocrine-driven changes return to normal rapidly
Uterine muscle rapidly looses oedema but contracts slowly: never returns to pre-pregnancy size
Removal of steroids permits action of raised prolactin on breast
Cardiovascular adaptation will return to normal within 2 weeks post-delivery
