Antenatal screening Flashcards
What are the principles of screening
Sensitivity = true positive rate Specificity = true negative rate Positive predictive value Easily used in large populations Safe and cheap
when is the booking appointment
8-12 weeks
What is done in the booking appointment
History Examination - BP, BMI, CVS and abdo exams FBC - Hb G&S - Ab, ABO, Rh STI check Urinalysis USS Estimated date of delivery
How can you estimate the due date in the booking appointment
Naegele’s rule = LMP + 9 months and 7 days
Crown Rump Length (CRL) = length from head to bottom (more accurate)
What does USS assess on the booking visit
viability of pregnancy - foetal heart singleton vs multiple in utero gestational age major structural anomalies Downs syndrome screening offered
What is done on follow up visits
BP, urinalysis physical and mental health assessment symphyseal fundal height lie and presentation foetal head engagement foetal heart auscultation
When is the foetal anomaly scan done
20 weeks
What can the foetal anomaly scan screening programme pick up
NTD cleft lip heart defects Abdominal wall defects - gastroschisis diaphragmatic hernia bilateral renal agenesis skeletal dysplasia Trisomies - Edwards (18), Pataus (13), Downs (21)
If you do not find any anomalies on scan this completely rules them out, true or false
False, need to know limitations of scans
What is placental previa
Low lying placenta obstructing the cervix
What is the bigest RF for having a baby with Down’s syndrome
Advanced maternal age
When can you have Downs screening and when is it more accurate
1st and 2nd trimester
More accurate in 1st trimester
What is measured in the 1st trimester for Downs screening
Nuchal thickness/translucency (NT) = measure of skin thickness behind foetal neck
PAPP-A levels = low
hCG levels = high
What is involved in 2nd trimester screening for Downs
Blood test at 15-20+6 weeks
hCG levels = high
AFP levels = low
What is measured in 2nd trimester screening for aneuploidy
Maternal age hCG AFP UE3 - unconjugated oestrodiol inhibin A
what is non-invasive pre natal testing (NIPT)
detects cell free foetal DNA (cffDNA)
identifies women at higher risk of trisomies
more accurate
not yet available but will be soon
what are specific diagnostic tests for Downs syndrome
amniocentesis
chorionic villus sampling CVS
When can amniocentesis be done and what is a risk
> 15 weeks
miscarriage
When can CVS be done and what is a risk
> 12 weeks
miscarriage
What are the main haemoglobulinopathies and what is their inheritance pattern
Sickle cell disease and thalamssemias
Autosomal recessive
Why is it important to check rhesus status
Rh+ father and Rh- mother could result in Rh+ baby in Rh- mother –> production of Rh antibodies in mother that circulate in her blood and can attack baby in future pregnancy causing Rh disease
What is given to RhD- mothers with Rh+ baby
Anti-D to mop up foetal blood that has gotten into maternal circulation through sensitising events
RhD+ mothers need anti-D, true or false
FALSE
What does urinalysis look for in antenatal checks
Proteinuria
glucosuria
leukocytes
ketonuria
How should you manage asymptomatic bacteriuria in pregnancy
Treat it!
What are risk factors for GDM (gestational diabetes)
BMI>30 previous GDM previous macrosomic baby >4.5kg FH of DM minority ethnicity
How do you diagnose GDM
OGTT
Fasting glucose >=5.1
2 hour plasma glucose >=8.5
SIGN guidelines ^^, differ from NICE
Who should a pregnant mother see if they are are on the green or red pathway
Green - midwife
Red - obstetrician and midwife support
When is symphyseal fundal height measured antenatally
from 24 weeks onwards
What are high risk factors for PET (Pre eclampsic toxaemia)
hypertensive disease during previous pregnancy autoimmune conditions CKD Type 1 or 2 DM chronic HTN
What are moderate RF for PET
1st pregnancy pregnancy interval >10 years BMI>35 FH of PET multiple pregnancy
How do you manage women at high risk of PET
150mg / low dose aspirin daily from 12wk –> birth
When is aspirin contraindicated
asthamatics
PUD
