Obs Physiology Flashcards
Role of Human Chorionic Gonadotrophin in pregnancy
Prevents corpus luteum degradation so that the CL can produce progestins until the placenta is formed.
Role of Progesterone in pregnancy
Source = corpus luteum then placenta.
Prepares endometrium and uterus for implantation by:
1) Proliferation, vascularisation and differentiation of endometrial stroma.
2)Promotes endometrial quiescence.
3) Increase maternal ventilation.
4) Promotes glucose deposition in fat stores.
Role of Oestrogen in pregnancy
Source = ovary then placenta.
Facilitates progesterone action by increasing progesterone receptors at endometrium.
Indicator of fetal wellbeing during pregnancy.
IgA in pregnancy
Secreted in breast milk
IgE in pregnancy
Mast cells, used in anaphylaxis
IgG in pregnancy
Only antibody able to cross placenta. Role in Rhesus disease with IgM.
Starts to cross at 16 weeks but majority is acquried in last 4 weeks.
Immunology of pregnancy
Increase in both T helper 1 and 2 cells but bias towards Th2. Trophoblast has non-immunogenic interface with mother.
Vascular changes at the uterus in pregnancy
Extra-Villus Trophoblast invade and remodel maternal spiral arteries. Invading chords form Primary villi which branch to form Secondary villi and then Free-floating villi. Penetrate to inner third of myometrium via decidua.
Maternal adaptations at the cervix
Increased vascularity
Reduction in collagen
Increased mucus secretions via gland hypertrophy
Maternal adaptations of the CV system
Increase cardiac output
Increase heart rate
Decrease in total peripheral resistance and decrease in blood pressure.
Increase red cell mass
Blood pressure initially falls and then rises in second half of pregnancy.
Maternal adaptations in the resp system
Lower maternal PaCO2 to allow better gas exchange with fetus.
Nutrients in pregnancy
Glucose main fatal energy substrate.
Hyperlipidaemia state for mother.
Thyroid function in pregnancy
Increases
Glomerular filtration rate in pregnancy
Increases
What maternal hormones are suppressed by placenta hormones
growth hormone, LH and FSH
How does glucose cross the placenta
Facilitated diffusion
Examples of molecules which cross placenta via simple diffusion
Ketones, urea.
Examples of molecules which cross placenta via active transport
Amino acids, water soluble vitamins.
Early pregnancy maternal glucose levels
Post-prandial levels are low
Late pregnancy maternal glucose levels
Post-prandial levels are high
Stages of labour
First stage = onset of labour to fully dilated cervix (10cm). Includes latent and active phase. Latent = irregular contractions, ‘show’, cervix effaces, to 3cm dilated. Active = dilation over 4cm to fully dilated, regular contractions, engagement of fetus’ presenting part.
Second stage = from full dilation to fetus is delivered. Passive stage until head reaches pelvic floor and desire for mum to push commences, active stage with pushing from mum.
Third stage = from fetal delivery to passing of placenta and membranes.
Features of labour onset
Painful, regular contractions
‘Show’ of mucus plug.
Cervix dilates (3cm) and effacement
Rupture of membranes can occur but is not defining feature.
Braxton Hicks contractions
Painless, intermittent catering contractions before labour onset.
3 factors which determine progress in labour
Passage - bony pelvis and resistance by soft tissue
Power - maternal uterine contraction force
Passenger - fetus
Cervical effacement
Cervical ripening = thinning of cervix and shortening as muscle fibres retract.
Accompanied by dilation.
Caused by raised COX-2 levels.
Stages of fetal descend in labour
Engagement Descent Flexion Internal rotation External rotation Restitution Lateral rotation
Types of cephalic presentation
Vertex/crown (normal) Sinciput (forehead first) Brow Face Chin
Types of breech presentation
Complete
Footling
Frank
Types of vertex presentation
According to position of occiput. Left, right or transverse? Anterior or posterior?
Best for fitting through pelvis is occiput-anterior and is mostly commonly left.
Endocrinology of labour
- Progesterone synthesis decreases due to corticotropin-releasing hormone. Oestrogen levels also drop.
- Ferguson’s reflex from stretched myometrium triggers oxytocin release from posterior pituitary gland. Causes smooth muscle contractions.
- Prostaglandins increase in labour to aid contractions via increasing myocyte contractility, ripen cervix and vasodilator small cervical vessels.
Trimesters
1 = 0 until 12+6 2 = 13+0 until 28+6 3 = 28+6 until birth/40
Hb in pregnancy
Physiological anaemia (low Hb), but increase red cell volume
4 functions of the placenta
Gas exchange
Endocrine (betahCG, progesterone etc)
Nutrient and waste product exchange
Barrier for infection
Non-worrying murmur in pregnancy woman
Ejection systolic murmur
Length of 3rd stage of labour
5-30 mins, over 30 mins increases PPH risk.
Rate of dilation in active first stage of labour
0.5-1.0 cm/hour. Nulliparous = 1.2cm/hr and multiparous 1.5cm/hr. If active first stage is over 2hrs look for cause.
Length of second stage of labour
Consider interventions if
>2hrs for a nulliparous woman
>1hr for a multiparous woman
What can you use to track labour progress
Partogram
Pattern of rise and fall of human chorionic gonadotrophin hormone
Detectable 8days after conception.
Levels double every 48hrs in the first weeks of pregnancy. Reach peak at 10weeks of 80,000mIU/ml and then fall to 10,000mIU/ml for rest of pregnancy.
Role of human placental lactogen hormone in pregnancy?
Mobilise glucose from fat reserves.
Increase blood glucose levels.
encourage mammary glands to become milk secreting tissues.
Surfactant production by fetus
24 weeks
When does the fetal heart start beating
4-5 weeks
Discuss fetal haemoglobin and the changes on the oxygen saturation curve
HbF has higher affinity to oxygen than HbA (adult). This allows the oxygen in the mothers blood to transfer down to the fetus’ haemoglobin which has a stronger attraction to the oxygen.
HbA starts to be created at about 32-34 weeks.
LEFT SHIFT ON CURVE
