Anatomy and physiology of pregnancy Flashcards
Describe the diameters of the pelvis in terms of transverse, oblique and anterior posterior
-Pelvic inlet
-Pelvic cavity
-Pelvic outlet
- Pelvic inlet
-Transverse diameter - 13cm - largest
-Oblique diameter - 12cm
-AP diameter - 11cm - Pelvic cavity
-Transverse diameter - 12cm
-Oblique diameter 13cm - largest
-AP diameter 12cm - Pelvic outlet
-Transver diameter - 11cm
-Oblique diameter - 12cm
-AP diameter 13cm - largest
Discuss the dimensions of the fetal head
-Submentobregmatic (face presentation)
-Verticomental (Brow presentation)
-Occipitofrontal (deflexed presentation)
-Occipitomental
-Suboccipitobregmatic dimension (Vertex presentation)
- Submentobregmatic 9.5cm narrowest diamter
- Verticomental brow - 13.5cm widest diameter
- Occipitofrontal - 11.5cm
- Occipitomental 12.5cm
- Suboccipitobregmatic 9.5cm narrowest diamter
Discuss the cardiovascular changes in pregnancy
-Vasodilation (2)
-Cardiac output (2)
-Blood pressure (4)
-Murmurs (1)
-Arrythmias (2)
- Vasodilation
-Increases by 30%
-Mediated by nitric oxide synthesis and prostaglandins - Cardiac output (stroke volume x HR)
-Increases due to stroke volume 10-30% from increased end diastolic volume and increase ventricle contractility
2’ to hypertrophy
-Increased heart rate - 10-20 bpm - Blood pressure ( SV x HR x PVR)
-Drops due to increased PVR to a nadir at 22-24 weeks
-Rises to pre pregnancy level at term
-Falls immediately post partum then peaks day 3-6
-Drops 25% in supine position - Ejection systolic murmur in 90% of women
- Premature atrial and ventricular beats = common, paroxsymal atrial tachycardia = common
Discuss impact of pregnancy on maternal ventilation
-Minute ventilation (2)
-Oxygen consumption (1)
-Respitratory rate (1)
-Maternal hyperventilation (3)
-Impact of progesterone on respiration (3)
-Mechanism of breathlessness in pregnancy (2)
- Minute ventilation = tidal volume x resp rate
-Increases by 40-50%
-Mostly due to increase in tidal volume by 200mL 2’ to progesterone - Oxygen consumption increased by 20%
- Respiratory rate - no change
- Maternal hyperventilation
-Results in mild respiratory alkalosis
-reduces the pO2 and pCO2 gradient to increase O2 for fetus
-Mother has decreased buffering capacity to manage acids so increased hyperventilation - Progesterone impact to respiratory changes:
-Increased bronchodilation
-stimulation of respiratory center
-Increased respiratory sensitivity to CO2 - Breathlessness in pregnancy driven by maternal hyperventilation and elevated diaphram
-Expereinced by 75% of women
Discuss haematological changes in pregnancy to
-Volumes of blood, plasma, erythrocytes (4)
-WCC (2)
-Platelets
-Clotting factors (5)
- Increased volumes
-Blood - 40%
-Plasma - 50%
-Erythrocyte volume - 20%
-Leads to dilutional anaemia with lower Hb and Hct.No change in MCV or MCH - WCC increases up to 16 is normal in pregnancy. Up to 18 is normal in labour
- Platelets drop but stays within normal limits
- Pregnancy hypercoagulable state
-Increased clotting factors 8,9,10
-Increased fibrinogen (Up to 50%)
-Decreased fibrinolytics
-Decreased antithrombin and protien S
-APTT, PT and TT remain normal
Discuss metabolic changes in pregnancy
-Changes to insulin (3)
-Drivers of insulin resistance (4)
-Changes to insulin requirments during pregnacy (2)
-Changes to maternal fuel types (2)
-Renal management of glucose (2)
- Changes to insulin
-Pregnancy is a diabetogenic state
-Increased insulin resistance and glucose intolerance
-Fasting glucose levels lower in pregnancy - Insulin resistance is driven by:
-Cortisol, progesterone, oestrogen, human placental lactogen. - Changing insulin requirments
-T1 = Increased insulin sesntivity = low insulin requirment and hypoglycemia.
-T2 and T3 = increased insulin resistance = hyperglycemia - Increased use of lipolysis and ketogenesis
- Renal management of glucose
-Renal tubular threshold drops leading to glucosuria
-There is no correlation between plasma and urinary glucose
Discuss pituitary changes in pregnancy (4)
-Volume of anterior pituitary increased 35%
-Prolactin increases 10 fold
-FSH and LH are suppressed
-ACTH and ARH remain unchanged
Discuss the impact of the placenta on:
-Cortisol (2)
-Renin-angiostensin aldosterone (3)
- The placenta produces ACTH and ARH this increases:
-cortisol 3 fold by term
-increased hepatic synthesis of cortisol binding globulin - ARA system
-Angiotensin II is increased 2-4 fold
-Renin activity increases 2-3 fold
-Aldosterone increases 3 fold in first trimester to 10 fold by term
Discuss the impact of pregnancy on the thyroid (5)
- Increased hepatic synthesis of thyroid binding globulin
- Total levels of T4 and T3 increase but free T3/4 are reduced.
- TSH rise and then fall in T1 then rise in T2 and T3.
- Increased renal loss of iodine from transfer to fetus and increased renal loss causing iodine deficiency
- Increased uptake of iodine by thyroid = 3 fold
What are the ranges of TSH in:
-Non-pregnant
-T1
-T2
-T3
- Non pregnant - 0.27 - 4.2
- T1 - 0-5.5
- T2 0.5 - 3.5
- 0.5 - 4.0
Discuss the impact of pregnancy on the gastro-intestine tract
-Impact of progesterone (5)
-Impact of oestrogen (2)
-Changes to liver (3)
- Progesterone decreases smooth muscle mobility causing
-decreased oesophageal pressure
-Decreased gastric peristalsis
-Delayed gastric emptying
-Decreased gall bladder emptying
-Decreased gastric motility - Oestrogen causes:
-Increased serum cholesterone
-Increased bile salt synthesis - Increased liver metabolism
-Increased fibrinogen synthesis
-Increased Thyroid binding globulin
-Increased corticosteriod binding globulin
Discuss renal changes during pregnancy
1. Physical changes to the kidney (4)
2. Blood flow changes
3. GFR rate changes
4. Protien excretion
5. Impact on bladder (2)
6. Sodium and water changes
7. Changes to renal endocrine functions (3)
- Physical changes to the kidney
Dilitation of the urinary collecting system
-progesterone induced smooth muscle relaxation of ureters, calyces and bladder
-compression of ureters
-Hydronephrosis with pelvicalyceal diameter of 5mm on L and 15mm on R kidney.
-R kidney larger than left secondary to uterine detrorotation - Increased blood flow by 80%
- Increased GFR. CrCl 50% increase. Leads to protien and glucosuria
- Increased protien excretion
- Impact to bladder
-increased vascular tortuosity - microscopic haematuria
-UTI and pyelo from urinary stasis - Salt and water changes
-Increased retention of salt and water secondary to RAS system - Renal endocrine changes
-Increase in renin and aldosterone production
-Increased erythropoietin production - increased RBC
-Increase in Vit D production
Discuss the MSK changes in pregnancy (4)
MSK changes mediated by progesterone and relaxin
-Relaxation of ligaments and muscles
-Accentuation of lumbar lordosis
-Symphsis pubis diastasis
-Swelling of soft tissue resulting in carple tunnel and sciatica
