Physiology 2 Flashcards
Which endocrine changes occur during the pregnancy?
Increase in oestrogen (from placenta) + progesterone (from corpus luteum + later from placenta)
Increase in thyroid binding globulin (TBG)
Increase in anti-insulin hormones:
- human placental lactogen
- prolactin
- cortisol
Increase in lipolysis as alternative energy source
What is the result of an increase in TBG during pregnancy?
More T3 + T4 bind to TBG
–> more TSH released from anterior pituitary
Therefore, free T3 and T4 levels remain the same but TOTAL T3 + T4 levels rise
Why do the changes in TBG in pregnancy occur?
Thyroxin is essential for the foetus’ neural development
–> ensures constant supply to foetus in early pregnancy
What do the anti-insulin hormones do in pregnancy?
Increase insulin resistance + reduce peripheral uptake of glucose
–> ensures constant supply of glucose for foetus
What is the risk of increased lipolysis during pregnancy?
Increased risk of ketoacidosis
Which cardiovascular adaptations occur during pregnancy?
Progesterone –> decreased SVR –> decrease in diastolic BP during first + second trimesters
In response, CO increases by about 30-50%
Total blood volume increases due to activation of RAAS
Which respiratory adaptations occur during pregnancy?
Increase in total volume + ventilation rate to match increased oxygen demand
Hyperventilation is common and can cause respiratory alkalosis
Which changes in the urinary system occur during pregnancy?
Increase in CO –> increase in renal plasma flow –> increase in GRF by about 50-60%
(urea + creatinine will be lower)
Relaxation of ureter + bladder –> increased risk of UTIs
Which haematological changes occur during pregnancy?
Increased risk of VTE due to:
- increase in fibrinogen + clotting factors
- decrease in fibrinolysis
- stasis of blood + venodilation
Plasma volume increase –> physiological dilutional anaemia
How can an increased risk of VTE be treated in pregnancy?
LMWH
NOT warfarin - teratogenic
What is the most common site of ectopic implantation?
Ampulla of the fallopian tube
What are Braxton Hicks contractions?
Irregular, involuntary contractions of the uterine smooth muscle that occur during the third trimester
(not part of labour)
Which 2 things need to happen for labour to commence?
Cervical ripening
Myometrial excitability
When is a women typically considered to be in labour?
When regular, painful contractions lead to effacement and dilatation of the cervix
What is cervical ripening?
Softening of the cervix that occurs before labour
- without this, the cervix cannot dilate
Which substance is particularly important for cervical ripening?
Prostaglandins
Which hormonal change is responsible for myometrial excitability?
Decrease in progesterone in relation to oestrogen
Which chemical is responsible for initiating uterine contractions?
Oxytocin (from posterior pituitary)
What are the stages of labour?
First stage (latent + active phase)
Second stage (passive + active stage)
Delivery
Third stage
When is a women considered to be in the first stage of labour?
From the beginning of labour until the cervix is fully dilated (10cm)
How regular are contractions in the first stage of labour?
Every 2-3 minutes
What happens during the latent phase of the first stage of labour?
Slow cervical dilatation over several hours until reaches 4 cm
What happens during the active phase of the first stage of labour?
Faster rate of cervical dilatation up to 10cm
- 1cm/hr in nulliparous women
- 2cm/hr in multiparous women
When is a women considered to be in the second stage of labour?
From full dilatation of the cervix until the foetus has been expelled
What happens during the second stage of labour?
Passive stage:
- until the head reaches the pelvic floor
- rotation + flexion of the head
Active stage:
- pressure of head on pelvic floor –> urge to push
- woman pushes in conjunction with her contractions to expel foetus
Which two hormones make contractions more forceful and frequent during the second stage of labour?
Prostaglandins (increase force)
Oxytocin (increases frequency)
How long should the active second stage last?
40 minutes in nulliparous women
20 minutes in multiparous women
- if it takes > 1 hour, spontaneous delivery becomes unlikely
How does the foetal hand position assist with delivery?
Once head reaches perineum –> extends
Following delivery of the head –> rotates 90 degrees to help delivery of shoulders
How are the shoulders delivered?
Anterior shoulder first, coming under the pubic symphysis
Then posterior should
When is a woman considered to be in the third stage of labour?
Following delivery of the foetus until the placenta has been delivered
How long does the their stage typically last?
About 15 minutes
How much blood loss in normal in the third stage of labour?
Up to 500ml
How is bleeding normally controlled during the third stage of labour?
Contraction of the uterus constricts blood vessels
Pressure is exerted on placental site by walls of contracting uterus
Normal blood clotting mechanism
What are the three main methods of artificially inducing labour?
Vaginal prostaglandins
Amniotomy
Membrane sweep
What are the complications of artificial induction of labour?
Failure of induction
Uterine hyperstimulation
Increased rate of further interventions (compared to spontaneous labour)
What is colostrum?
Breast milk produced immediately after birth
- less water soluble vitamins, fat and sugar than mature milk
- more proteins (esp Ig) and fat soluble vitamins
Which hormone regulates breast milk production?
Prolactin (from anterior pituitary)
Which hormone controls prolactin secretion?
Dopamine (from hypothalamus) INHIBITS prolactin
Also stimulated by suckling
Where does the inguinal ligament lie?
Between the ASIS and the pubic tubercle
In what position should the foetal head enter the pelvic cavity and why?
Facing either to the left or to the right
- at pelvic inlet, transverse diameter is wider than AP diameter
- occipitofrontal diameter is longer than the biparietal diameter of the foetal skull
What is the ‘station’ referring to?
Distance of the foetal head from the ischial spines
- negative number means the head is superior to the spines
- positive number means the head is inferior to the spines
When descending through the pelvis cavity, what position should the foetal head be in?
Flexed (chin on chest)
and rotating
In what position should the foetal head pass through the pelvic outlet?
Ideally occipitoanterior (OA)
What position should the foetal head be in during delivery?
Extension
