Maternal changes in pregnancy Flashcards
What are 6 events that occur to cope with the changes during pregnancy?
- increase in size of uterus
- increased metabolic requirements of uterus
- structural + metabolic requirements of fetus
- removal of fetal waste products
- provision of amniotic fluid
- preparation for delivery + puerperium (first 6 weeks)
In which systems do major changes occur?
- energy balance
- respiratory
- cardiovascular
- gastrointestinal
- urinary
- endocrine
Which hormones cause most of the changes?
- maternal steroids - placenta takes over ovarian (CL) production around week 7
- placental peptides - hCG, hPL, GH
- placental + foetal steroids - progesterone, oestradiol, oestriol
- maternal + fetal pituitary hormones - GH, thyroid hormones, prolactin, CRF
Where is the effect of placental steroids?
- renin-angiotensin system
- respiratory centre
- GI tract
- blood vessels
- uterine myometrial contractility
What is the total weight gain during pregnancy?
-
12.5-13kg
- fetus + placenta = 5kg
- fat + protein = 4.5kg
- body water = 1.5kg
- breasts = 1kg
- uterus = 0.5-1kg
- ideally keep to less than 13kg
- failure to gain or sudden change needs monitoring
Why will a mother need to increase energy?
- output: to cope w/ increased respiration + cardiac output
- input: for fetus, labour + puerperium
Why is there a gain in fat and protein stores?
- 4-5kg
- increased consumption + reduced use
- mainly laid down in anterior abdominal wall
- utilised later in pregnancy + puerperium
What happens to the basal metabolic rate?
rises by:
- 350 kcal/day mid gestation
- 250 kcal/day late gestation
- usage: 75% fetus and uterus, 25% respiration (H&L)
- 9 calories = 1g fat, therefore 40g fat for 350kcal ie 1 large mars bar
When is glucose important in pregnancy?
Need increased levels in blood in 2nd trimester
How does the glucose get to the fetus?
- active transport across placenta as fetal energy source
- fetus stores some in liver
What happens in the 1st trimester with glucose?
- maternal reserves
- pancreatic B-cells inc in number
- plasma insulin increases so more goes into tissues
- laid down as stores + used by muscle
- fasting serum glucose decreases
What happens in the 2nd trimester with glucose?
- fetal reserves
- hPL causs insulin resistance
- ie less glucose into stores
- increase in serum glucose
- more crosses placenta
- but can cause diabetes
What are the reasons for increased water wain?
- E2 and P act on renin angiontensin system
- fluid retention possible due to sodium retention
- resetting of the osmostat
- decrease thirst threshold
- decrease in plasma oncotic pressure (albumin)
How is oxygen consumption increased?
- stimulated by E2 and P
- increases respiratory centre sensitivity to CO2
- thoracic anatomy changes.. ribcage displaced upwards, ribs flare outwards
- breathe more deeply
- minute volume increases 40%
- arterial PO2 increases 10%, PCO2 decreases 15-20%
- this facilitates placental gas transfer
What happens to the maternal blood content?
- Hb concentration will measure slightly lower due to higher intravascular fluid (haemodilution)
- red cell mass should rise (18%)
- placenta in fetuses are also iron-hungry
- increaseded efficiency of iron absorption from gut
- white cells increase
- blood becomes hypercoagulable = inc fibrinogen for placental separation, but inc risk of thrombosis
What happens to the foetal blood?
- increased Hb and altered in type
- increased O2 binding
- oxygen given up by maternal Hb
What does smoking do to the fetus?
- increases maternal carboxy-Hb
- it’s more permanent
- reduces the increased binding
- fetal hypoxia
The expanding uterus pushes heart round, there are changes in ECG + heart sounds. What happens to the cardiac output?
- increased cardiac output
- due to increased HR + SV
- begins as early as 3 weeks to max at 40% at 28 weeks
- for maternal muscle and fetal supply
What happens to the peripheral vascular system?
- inc CO + vasodilation by steroids
- -> reduced peripheral resistance
- inc flow to:
- uterus, placenta, muscle, kidney + skin
- neoangiogenesis - including extra capillaries in skin (spider naevi) to assist in heat loss
What happens in the GI tract?
steroids cause…
- appetite + thirst
- reduced GIT motility -> constipation
- relax lower oesophageal sphincter -> acid reflux
- large uterus -> acid reflux + smaller freq meals
Supplementation of folic acid advice is 400micrograms/day up to week 12. Why is folic acid supplementation important?
- DNA production, growth + blood cells (for uterus, placenta, fetus)
- deficiency linked to spina bifida - neural tube defect
What happens to the urinary tract?
- dilates, relaxes
- increased UTI (may persist)
What happens to the kidney?
- increased blood flow
- increased filtration rate
- increase clearance of creatinine, urea, uric acid
What changes occur in uterine size?
- huge increase in muscle mass (x20)
- huge increase in blood flow
- placenta + uterus = 1/6 of total
