3.4 - Ultrasound and Foetal Wellbeing Flashcards
When is the 1st trimester ultrasound typically performed?
Give 3 things you are looking for (role of US)
Typically performed at booking clinic => around week 12 (11-13). despite first trimester technically ending at week 12+6
1) Location of pregnancy (to rule out ectopic)
2) Viability of pregnancy
3) Confirm EDD vs LMP (>=5 discrepancy if 6-12 weeks and >=7 if 14+ weeks)
4) singleton vs multiple gestation (confirm chorionicity)
What is measured to confirm EDD in the first trimester US?
Crown-rump length vs LMP (>=5 discrepancy if 6-12 weeks and >=7 if 14+ weeks)
When is the 2nd trimester ultrasound typically performed?
Give 3 things you are looking for (role of US)
Weeks 18-22 (2nd trimester between 13-27+6)
1) Fetal anomaly scan (exclude CHD, NTD, obv chromosomal abnormalities)
2) Confirm placental location (exclude abnormal placentation)
3) Confirm EDD again
How is EDD measured in the 2nd trimester US?
BP (biparietal) diameter
Femur length
Abdominal circumference
Head circumference
Note: These are the same as how it is measured in 3rd trimester
Which parameters used to measure EDD in the 2nd trimester is best used to assess foetal growth?
Abdominal circumference (GA+/-2)
Same as SFH
When are 3rd trimester US scans typically performed?
What are you looking for? Give 3
Couldnt give you a bigger hint that there are multiple
Conducted Biweekly when attending OPD/GP before becoming weekly after 36 weeks.
1) Assess foetal size AND Estimated foetal weight (ESW)
2) Confirm placental location
3) Confirm fetal presentation
4) Evaluate volume of amniotic fluid for foetal wellbeing
How do you find the Estimated Foetal weight?
In 3rd trimester foetal ultrasound scans using the same parameters for size:
BP (biparietal) diameter
Femur length
Abdominal circumference
Head circumference
These are then compared to centiles for gestational age
Give 5 methods of antepartum surveillance of foetal wellbeing
1) Maternal perception of foetal activity
2) US evaluation of liquor volume (Also for monitoring foetal growth)
3) BPP - Biophysical profile
4) Doppler US
5) CTG
In the 3rd trimester, the foetus spends 10% of its time making gross body movements. All women should be encouraged to self-monitor foetal movements and advised to come to hospital if there is reduced foetal movements or changes in the frequency. How would you advise the woman to keep track of this?
Cardiff Count-to-10 chart
This is recommended routinely from 3rd trimester => 28 weeks. 60% accuracy
How is BPP (Biophysical profile) performed?
US
What parameters are measured for BPP (Biophysical profile)?
How do you interpret the results
Fetal hypoxia causes:
1) reduced CNS activity => Fetal tone
2) reduced gross movements => fetal gross body movements
3) reduced breathing => fetal breathing movement
4) reduced renal flow => Amniotic fluid volume
Scores are either 0 or 2
0,2,4 => concerning
6 => monitor
8 => reassuring
How is US doppler measured?
US doppler of Umbilical and Middle cerebral artery
What is the etiology of a pathological US doppler?
Give 4 causes
Increased resistance to flow (vascular resistance) causing foetal hypoxia. This is typically due to placental insufficiency => same causes as late decelerations
Acutely:
Maternal hypotension
Placental abruption
Antepartum hemorrhage
Rhesus isoimmunisation
Chronic:
GDM
Hypertension/PET
Renal disease
TTTS
Resistance in the umbilical artery is typically so low that flow continues even in diastole. What is shown in this image?
Absent End-diastolic flow
What is shown in this image?
What does this indicate in terms of management?
Reversed Diastolic flow
Emergency C-section
