Pregnancy Physiology Flashcards
What is the role of the placenta?
Acts as the foetal lungs
Supplies foetus with oxygen and removes CO2
What 3 factors facilitate the supply of oxygen to the foetus?
- Foetal Hb- increased ability to carry O2
- Higher Hb concentration in foetal blood- 50% more than in adults
- Bohr effect- Foetal Hb can carry more O2 in low pCO2 than in high pCO2
Describe the way in which water and electrolytes pass from the mother to foetus via the placenta
Water diffuses into the placenta along osmotic gradient- this exchnage increases during pregnancy up until the 35th week
Electrolytes follow water
Iron and Calcium can only go from mother to foetus
What is the role of HCG on the corpus luteum?
Prevents involution in the first 12 weeks of pregnancy
The CL stimulates progesterone and oestrogens
What is the role of progesterone?
- Development of the decidual cells
- Decreases uterine contractility
- Prepares for lactation
What role do the oestrogens play?
- Enlargement of uterus
- Breast development
- Relaxation of the ligaments in preperation for birth
True or false?
In early pregnancy the levels of HCG double every 24 hours
False
Levels double every 48 hours
Why is nausea and vomiting seen in the first trimester?
It is a side effect of HCG
The levels of HCG start to fall around 12-14 weeks and so does its side effects
During pregnancy, how much does the mother’s CO increase by?
Around 30-50%
(begining around week 6 and peaking week 24)
Why does a mother’s HR increase during pregnancy?
In order to increase CO- increases to around 90 bpm
Describe how blood pressure changes throughout pregnancy
- BP initially falls, reaching its lowest point in the 2nd semester
- At its lowest it is around 15mmHg lower than the pre-pregnancy BP
- In the 3rd trimester BP rises, reaching pre-pregnancy levels by term
What 3 big changes occur in the blood of the mother?
- Plasma volume increases proportionatley with CO (50%)
- erythropoesis (RBC) increase by 25%
- Hb is decreased by dilution (RBC increase) which increases the blood viscosity
Outwith pregnancy, what is the normal limit of blood iron?
Hb 120-160g/L
What is the ranges for diagnosing anaemia in pregnant women?
First trimester Hb < 110g/L
2nd and 3rd trimester Hb < 105g/L
Why do changes in lung function come about in pregnancy?
Partly as a result of progesterone increase (P signals brain to lower CO2 levels)
Also because the enlarging uterus interferes with lung function
In pregnancy, how are CO2 levels lowered? (4)
- respiratory rate increases
- tidal and minute volume increases by 50%
- pCO2 decreases slightly
- Vital capacity and pO2 dont change
In pregnancy, how do postural changes affect renal function?
Upright position- decreases
Supine position- increases
Lateral position whilst asleep- really increases
What happens to GFR in pregnancy?
Increases around 30-50% (peaks 16-24 weeks)
How does a mother’s coagulation change through pregnancy?
- Hypercoagulable state
- This reduces risk of haemorrhage during and after delivery
- However, increases risk of VTE
What is the average weight gain of a mother during pregnancy?
11kg (can be as much as 30)
How many extra calories does a pregnant women need to consume each day?
Around 200 kcal
How are the metabolic phases of pregnancy split up?
Into 2 phases
First phase is the mother’s anabolic phase- week 1-20
Weeks 21-40 is the catabolic phase
Describe the metabolic demands of the foetus on the mother?
- Weeks 1-20 (mother’s anabolic phase)- small nutritional demand from the conceptus
- From weeks 21-40- foetus has high metabolic demands and so there is accelerated starvation of the mother
What happens to the mother in the anabolic phase?
- Normal or increases sensitivity to insulin
- Lower plasmatic glucose level
- Lipogenesis, glycogen stores increase
- Growth of breasts and uterus- weight gain
What happens to the mother in the catabolic phase (accelerated starvation)?
- Maternal insulin resistence
- Increased transport of nutrients through the placental membrane
- Lipolysis
What changes in hormones occurs during parturition?
-
Eostrogen:Progesterone ratio alters which increases excitability.
- Progesterone inhibits contractility
- Oestrogen increases contractility
- Prostaglandins are produced by the placenta, myometrium, decidua, and membranes
- Oxytocin is released which increases contractions and excitability
What part of the pituitary releases oxytocin?
Posterior pituitary gland
What hormone is further released as the cervix stretches?
Oxytocin
What is given to induce labour?
Prostaglandins and Oxytocin
Oxy is given IV, Prostaglandins are given as a gel or pessary
What is the role of prostaglandins during child birth?
Stimulates more vigorous contractions of the uterus
What are the 3 stages of labour?
- 1st Stage= cervical dilation (8-24 hours)
- 2nd Stage= passage of the foetus through the birth canal (minutes to 120 minutes)
- 3rd Stage= expulsion of the placenta
What are the roles of progesterone and oestrogen in regards to lactation?
Oestrogen - growth of the ductile system
Progesterone - development of the lobule-alveolar system
Both inhibit milk production and so drop at birth
What hormone stimulates milk production?
Prolactin
Around 1-7 days after birth, prolactin induces high milk production. Stimulates first milk (colostrum)
What hormone controls the milk ‘let-down’ reflex?
Oxytocin
True or False?
Oxytocin causes milk to be ejected from the nipple
True (causes smooth muscle contration)
