Antenatal Care & Screening Flashcards
how do you assess the sensitivity of a screening test?
true positive / (positive + false negative)
how do you assess the specificity of a screening test?
true negative / (negative + false positive)
what history and examination is taken at the booking visit?
history
- menstrual
- medical
- obstetric
- family
- social
examination
- Ht, Wt, BP, CVS and abdomen
how can an estimated due date be predicted?
naegeles rule predicts it based on onset of woman’s last menstrual period
*add on nine months and 7 days
what investigations are undertook at the booking visit?
Hb ABO; Rhesus syphillis, HIV, hep B and C urinalysis, MSSU, c&s ultrasound
what is the role of the US during the booking visit?
confirm viability singleton/multiple pregnancy estimate gestational age (most accurate method to determine EDD) detect major structural abnormalities offer DSS
what history and examinations are undertook during follow up antenatal visits?
history
- physical and mental health
- foetal movements
examination
- BP and urinalysis
- symphysis - fundal height
- lie and presentation
- engagement of presenting part
- foetal heart auscultation
what is placenta praevia?
when the placenta is low lying in the womb and covers all or part of the cervix
*in most women, as womb grows upwards, the placenta moves with it so that it is in normal position before birth
what should you be offered if an earlier US scan (approx 20 weeks) showed that placenta extends over cervix?
should be offered another abdominal scan at 32 weeks
if this second scan is unclear, should be offered a vaginal scan
how is downs syndrome risk assessment carried out in the first trimester?
measure of skin thickness behind foetal neck using US (nuchal thickness: NT)
- measured at 11-13+6 weeks
- combined with HCG and PAPP-A
- a value of <3.5mm would be considered normal when CRL is between 45 and 84mm
how is downs syndrome risk assessment carried out in second trimester?
blood sample at 15-20 weeks
assay of HCG and AFP
- use combo of these, 1st trimester results and maternal age and gestation to give personal risk
- > 1:250 high risk and requires further investigation eg amniocentesis
in whom is second trimester screening for aneuploidy carried out and what tests are performed?
for those who miss first trimester screening or those who CUBS is unsuccessful
use maternal age + biochemical markers
- AFP
- hCG
- UE3
- inhibin A
what specific diagnostic tests can be carried out for chromosomal abnormalities?
amniocentesis
- usually after 15 weeks
- 1% miscarriage risk
chronic villus sampling
- usually after 12 weeks
- 2% miscarriage risk
what are the two main hereditary haemoglobin disorders?
HbS
thalassemias
what can cause maternal anaemia?
iron deficiency
folate deficiency
B12 deficiency
*screened at booking and 28 weeks
