Growth, Liquor, Dopplers Flashcards
Discuss uterine artery dopplers
-When to measure (2)
-Who to measure on (2)
-What it measures (3)
-What is abnormal (2)
-How it should be used in management (5)
- When to measure
-20 - 24 weeks gestation
-If abnormal at 20 weeks repeat at 24 weeks - Who to measure
-Women at risk of SGA and PET, current HTN disorder - What it measures
-Shows flow resistance on maternal side of the placenta
-Suggests maternal cause for growth restriction - What is abnormal
-Notching after 24 weeks
->95% percentile is abnormal
5 How it can be used in management
-Can be used to at time of diagnosis of SGA
-Helps predict risk of early onset IUGR
-Can help differentiate the SGA from IUGR babies
-If abnormal offer serial growth scans
-If normal offer third trimester growth scans
Discuss the pathophysiology of uterine artery dopplers
-Defective replacement of spiral arteries by trophoblasts results in failure to convert high resistance maternal arteries into low resistance channels resulting in poor blood supply to placenta and therefore fetus
Discuss umbilical artery dopplers
-When to measure (7)
-When should it not be done
-What it measures
-How to use in pregnancy
5. What is the frequency of doppler investigation
- When to measure
-SGA baby
-EFW <10th
-EFW dropped by >30 centiles
-AC less than 5th centile on population chart
-Discrepancy between head and abdo circumference > 30% with AC being lower
-Maternal HTN disorder
-Decreased FM - When should it not be done
-In normal pregnancies with no maternal or fetal risk factors - What does it measure
-Provides information about the fetal side of the placenta.
-Reflects downstream resistance at the placental stem and terminal villi - Use in pregnancy
-Primary surveillance screen in SGA
-Use has been shown to reduce perinatal mortality (Cochrane review)
-Use shows reduced CS and IOL if used - Frequency of doppler
-If SGA/IUGR and normal UAPI do fortnightly
-If SGA/IUGR and abnormal UAPI do twice weekly
-If SGA/IUGR and abnormal with AEDF or REDF do daily
Discuss umbilical artery dopplers
-Pathophysiology
-Progression
-What is an abnormal UAPI
- Pathophysiology
-Abnormal spiral artery remodelling leads to prolonged reduction in maternal intervillous perfusion
-Leads to reduced oxygen delivery to the fetal surface of the placenta
-Results in vasoconstriction of the stem villi
-Results in increased resistance to flow from fetus to the placenta - Progression
-Usually the resistance in the umbilical arteries drops as gestation increases
-30% of villous vascular dysfunction = increased UAPI
-60% of villous vascular dysfunction = AEDF/REDF
-In early onset IUGR with abnormal dopplers the time between AEDF and REDF may be weeks
-In third trimester the interval between AEDF and REDF is shorter - Abnormal UAPI = >95%
How should umbilical artery doppler be measured (6 points)
- Perform when baby is not moving
- Always keep Tlb <0.5 by reducing acoustic power output
- Identify free loop of umbilical cord
- Try to position the beam so the blood flow is parallel or at least has an angle less than 60 degrees
- Get spectral trace
- Freeze image when 5 symetrical wave forms have been obtained
Describe the umbilical wave forms for
1. Normal pregnancy
2. Reduced end diastolic flow
3. Absent end diastolic flow
4. Reversed end diastolic flow
Discuss middle cerebral artery dopplers
-When to measure (3)
-What it measures (5)
-Use in pregnancy (3)
-What is an abnormal MCA
- When to use
-SGA/IUGR and >34weeks regardless of UAPI
-SGA/IUGR and <34 if UAPI abnormal - What it measures
-Measures fetal brain arterial circulation.
-Normally shows high resistance pattern
-Low resistance pattern abnormal
-Reflects chronic hypoxia not acidemia
-Correlates poorly with acidemia at birth - Use in pregnancy (No longer used in NZ)
-If <34 weeks do not use to time delivery
-If>34 weeks time delivery at 38-39 weeks
-If abnormal chance of CS 68% - Abnormal MCA PI <5th centile
Discuss the pathophysiology of middle cerebral artery doppler
-Placental insufficiency leads to chronic hypoxia
-Brain arteries vasodilate to enhance local perfusion
-Resistance in vessels drops
-Once resistance as low as possible the MCA is no longer useful to predict worsening hypoxia
-Normalisation of MCA can reflect auto regulatory dysfunction as fetus no longer responding appropriately to hypoxic environment - be worried if MCA normalises and everything else abnormal
Discuss cerebral placental ratio
-When to measure
-What it measures
-Use in pregnancy (now used in NZ for timing)
-What is an abnormal CPR
- When to measure
-If MCA is performed then CPR should be calculated - What it measures
-Is a ratio of MCA: UAPI
-Represents fetal blood flow redistribution
-Predicts redistribution of cardiac output relative to cerebral blood flow - Use in pregnancy
-Might be useful in predicting at risk fetus whose individual parameters are normal
-May be useful in predicting baby’s that don’t tolerate labour
-If abnormal 58% chance of CS
-Ass with fetal distress, CS and NICU admission - Abnormal CPR = <5th centile
Discuss ductus venosus doppler
-When to measure (2)
-What it measures
-Use in pregnancy
- When to measure
-Abnormal dopplers <32 weeks - What it measures
-Flow through the ductus venosus which shunts blood from the umbilical vein to the IVC bypassing the liver
-Provides information about severe hypoxia and caridac health.
-Is a late sign of things going badly if abnormal - Use in pregnancy
-Best predictor of acidemia at birth in early onset fetal growth restriction
-Should be used to time delivery in SGA/IUGR babies who are preterm <32/40
-Deliver when there is an absent a wave indicating absent or reversed flow (Truffle trial)
Discuss ductus venosus dopplers
-Pathophysiology
-What is abnormal
- Pathophysiology
-Increasing arterial resistance leads to poor myocardial contractility and increased R heart pressures (effectively heart failure driven by HTN).
-Increased R heart pressure leads to reduced diastolic flow in the ductus venosus
-Reduced flow from DV means less oxygenated blood which results in increased DV dilatation to allow for increased blood flow
-Leads to loss of a wave - Abnormal findings
-DVPI is abnormal when >95%
-Absent A wave (Late finding)
Discuss MCA PSV doppler
-Indications
-How to interpret
-What it measures
- Indications
-Maternal fetal isoimmunisation
-Any suspicion of fetal anemia
-Unexplained hydrops
-MCDA twins >24 weeks gestation
-MCDA twins with known TTTS or TAPS - How to interpret
->1.5Mom is abnormal
-Differs with gestational age (MCA PSV increases) - What it measures
-A measure of anaemia
-Based on increased blood flow from increased cardiac output and reduced blood viscosity
-Predicts moderate to severe anaemia
-False positive rates increase after 35/40
Discuss fetal hydrops
-Definition (2)
-Incidence (2)
-Prognosis (4)
- Definition
-Excessive extravascular fluid accumulation
-Diagnosed by 2 or more of
-Pericardial effusion
-Pleural effusion
-Ascites
-Skin oedema
-Polyhydramnios
-Placental enlargement - Incidence
-1:1500 - 3500
Ratio of non-immune to immune 9:1 - Prognosis
-50-70% overall
-100% if associated with structural heart defect / TTTS / chromosomal abnormality
-Live birth rate 40-60%
-Those born alive have 60% chance of normal developmental outcomes
What are the causes of hydrops (6 groups)
- Immune
-Red blood cell alloimmunisation resulting in fetal haemolytic anemia - Chromosomal
-Turners, T21/13/18 - Haematological
-Thalassemia (Barts hydrops)
-Anaemia
-TTTS - Infection
-Parvovirus, CMV, Toxoplasmosis - Metabolic
-Glucose-6-phosphate dehydrogenase deficiency
-Pyruvate kinase deficiency - Structural
-Cardiac - primary cardiac failure, secondary cardiac heart failure
-Thoracic CPAM, congenital diaphragmatic hernia
-GIT - oesophageal atresia
-Renal - Low urine output from renal agenesis / obstruction
-Lymphatic obstruction
Discuss the pathophysiology of hydrops
Causes of hydrops feed into three main outcomes
-Endothelial failure = increased capillary leakage
-Liver failure = decreased oncotic pressure
-Heart failure = increased central venous pressure
These things result in increased fluid in the tissue
How should hydrops be investigated (7)
-Maternal blood group and screen for HDN antibodies
-Kliehauer to assess maternal fetal haemorrhage
-MCA PSV to assess fetal anaemia
-Maternal serology for infection
-Amnio for karyotype
-Fetal tertiary anatomy scan and echo for fetal heart defects
-Consider fetal blood sampling
How should hydrops be managed
-Antenatal (5)
-Delivery (4)
-Postpartum (3)
- Antenatal management
-Management depends on cause
-Consider intrauterine fetal transfusion if cause is fetal anaemia
-Transplacental anti-arrythmics if cause is fetal arrythmia
-Drainage of pleural effusions to prevent lung hypoplasia
-Laser photocoagulation of placental anastomosis in TTTS - Intrapartum management
-Delivery if maternal health at risk (PET)
-Consider delivery after 34 weeks
-Needs to be case by case
-Choice of delivery case by case - Postnatal management
-Deliver at a place with NICU. Will likely need resus
-Drain effusions
-Investigate for possible causes
Discuss maternal implications of fetal hydrops
-Fetal hydrops from any cause can result in maternal symptoms
-Can mimic PET or nephrotic syndrome
-Generalise oedema that mimics fetal sites of oedema
-Can occur at anytime and may persist postpartum but usually resolves
-Severe maternal complications in 21%
-Reversal of fetal hydrops or fetal demise reverses maternal symptoms
-Usually warrants prompt delivery as can deteriorate rapidly
Discuss fetal macrosomia
-Definition (3)
-Prevalence (2)
-Risk factors (10)
- Definition
-Macrosomia is >4kg or 4.5kg at any gestation
-No universally accepted definition
-LGA = Birth weight >90%
-RANZCOG guideline uses EFW/AC >95% - Prevalence
- 9% >4kg
- 0.1 >5kg - Risk factors
-Incorrectly dated gestation
- Constitutional
-Maternal diabetes
-Maternal obesity - 12.7% or 22% if GDM
-Excessive maternal weight gain
-AMA >30yrs
-Post dates
-Multiparity
-Previous macrosomic/LGA baby
-Ethnicity
-Male fetus