REPRO: Maternal Changes In Pregnancy Flashcards
What are some of the causative factors for the major maternal changes in pregnancy?
There are major changes in multiple systems that occur in the body during pregnancy. The causative factors are: - high levels of steroids - mechanical displacement - foetal requirements
Pregnancy is a physiological event. The systems (normally) return back to normal after delivery, but not all of them.
A pregnant female is considered a very different physiological being compared to normal males and females.
How can pregnancy abnormalities be diagnosed and what issues can pregnancy pose?
To diagnose an abnormality in pregnancy, we need to detect changes within the changes.
However, pregnancy may:
- exacerbate a pre-existing condition
- uncover a ‘hidden’ or mild condition
E.g. - Blood pressure increases during pregnancy. If a woman is obese, then she can become insulin resistant and become diabetic.
What are of the physiological changes of pregnancy?
The changes are designed to cope with several main events:
- increase in the size of the uterus
- increased metabolic requirements of the uterus
- structural and metabolic requirements of the foetus
- removal of foetal waste products
- provision of amniotic fluid
- preparation for delivery and puerperium (the period of about six weeks after childbirth during which the mother’s reproductive organs return to their original non-pregnant condition)
There are also changes in breast tissue for feeding.
List the systems that pregnancy causes changes in.
- cardiovascular system
- respiratory system
- gastrointestinal system
- urinary system
- endocrine system
- energy balance
Which hormones (peptides and steroids) are involved in pregnancy?
Placental peptides:
- hCG (human chorionic gonadotropin)
- hPL (human placental lactogen)
- GH
Maternal steroids:
- placenta takes over ovarian (CL) production around week 7
Placental and foetal steroids:
- progesterone
- oestradiol
- oestriol
Maternal and foetal pituitary hormones:
- GH
- thyroid hormones
- prolactin
- CRF (a.k.a CRH)
Where do the effects of placental steroids take place?
- renin/angiotensin system
- respiratory centre
- GI tract
- blood vessels
- uterine myometrial contractility (progesterone causes relaxation of uterus during pregnancy - changes during delivery)
Describe the distribution of weight gain during pregnancy.
The total weight gain is 12.5 to 13 kg. The average baby weighs 3.6kg.
Foetus plus placenta: 5 kg Fat and protein: 4.5 kg Body water: 1.5 kg (intravascular, interstitial, intracellular) Breasts: 1 kg Uterus: 0.5-1 kg
Ideally, the gain is kept to less than 13kg; failure to gain the weight or a sudden change needs monitoring.
How does our energy balance and basal metabolic rate change during pregnancy?
We need to increase our energy: OUTPUT: - to cope with the increased respiration and cardiac output. STORAGE: - for the foetus - for labour and puerperium
We gain 4-5kg in fat and protein stores. The reasons for this are:
- increased consumption and reduced use
- mainly laid down in the anterior abdominal wall
- utilised later in pregnancy and puerperium
Basal Metabolic Rate:
Increases by 350 kcal/day (mid gestation) or 250 kcal/day (late gestation).
- 75% to fetus and uterus
- 25% for respiration
*9 calories=1g fat therefore 40g fat for 350kcal i.e. 1 large Mars Bar
What are some requirements for glucose during pregnancy?
We need:
- an increased availability of glucose in the 2nd trimester
- Facilitated diffusion across the placenta as a foetal energy source
- foetus storing some glucose in its liver
How is glucose stored and utilised in different trimesters of pregnancy?
During the first trimester we used maternal reserves:
- pancreatic β cells increase in number
- plasma insulin increases
- fasting serum glucose decreases (laid down as stores and used by muscles)
During the second trimester, we use foetal reserves:
- hPL causes insulin resistance (ie. there is less glucose going to stores)
- there is increased availability of serum glucose (thus more crosses the placenta, however, it can cause diabetes)
Where does all the water gain come from?
The water gain during pregnancy can account for up to 8.51 litres, coming from:
- PLASMA VOLUME
- foetus
- placenta
- amniotic fluid (fetal urine filtered by mum - water - about 1L)
- oedema (lungs, connective tissue, ligaments, leakage, swollen ankles)
- uterine muscles
- mammary glands
How do we increase the plasma volume during pregnancy?
Plasma volume increases by around 40-50%.
- sodium retention
- resetting of the osmostat
- decreased thirst threshold
- decrease in plasma oncotic pressure (albumin)
(E2 and P act on the renin-angiotensin system)
How do Oestradiol (E2) and Progesterone (P) increase oxygen consumption?
E2 and P increase the respiratory centre sensitivity to CO2. The thoracic anatomy of the mother also changes, with the ribcage displacing upwards and the ribs flaring outwards.
These factors cause the mother to breathe more deeply, causing the minute volume to decrease by about 40%.
Thus, the arterial PO2 increases (by about 10%), and the PCO2 decreases (by about 15-20%).
This facilitates gas transfer between the mother and the foetus (high O2 levels in mum will cause diffusion of 02 to foetus and low CO2 levels in mum will cause diffusion of CO2 from foetus to mother).
How does maternal blood composition differ from normal blood composition, and what effect does that have?
The maternal plasma volume increases by about 40-50%, and the red cell mass increases by about 18-20%.
There is also an increase in white cells and clotting factors.
Due to the changes in volume and red cell mass, the haemoglobin concentration actually decreases. This is a phenomenon called haemodilution, where there is apparent anaemia due to the concentration of Hb falling, not the amount.
To make all the additional red blood cells, there is an increased efficiency of iron absorption in the gut.
Due to the increase in white blood cells and clotting factors, the blood becomes hypercoagulable. This means we will have increased fibrinogen for placental separation, but an increased risk of thrombosis. It is useful for stopping the mum bleeding to death at the end of pregnancy.
Oestrogen makes the liver produce lots of extra clotting factors.
How is the foetal blood able to take oxygen off of the mother’s blood?
Foetal blood has increased haemoglobin and is altered in type. This increases O2 binding capacity.
Thus, oxygen is given up by the maternal Hb.
Dissociation curve shifted to the left.
