Maternal screening Flashcards
Discuss the role of clinical biochemical tests in first and second trimester maternal screening
1st: more Sn to disease. Bchem Tests:
preg. assoc. plasm. Prot. A (PAPPA), free B HCG
2nd: unconjugated oestriol (uE3) from placenta, aFoeto protein (AFP), free B HCG
There is a high false positive rate (e.g. 5%) for the cut-off levels used for many of the tests used in first or second trimester screening.
a) What problems does this cause?
b) What would happen if the cut-off levels were changed to be more specific?
a) may cause harm? to person bc become concerned that they’re pos, maybe lead to inappropriate treatment?
b) If Inc Sp = dec Sn? (bad bc should be more Sn since screening)
How is the risk of an affected pregnancy determined?
Algorithm that combines:
+ pre-test risk: maternal age, Prev. Hx, weight
+ Biochemical MoMs (multiple of median)
+ Nuchal translucency
*Nuchal transluscency & age most important Risk F. give ~70% detection
a) What is NIPT and
b) what are its advantages compared to traditional first and second trimester testing
a) Non-invasive prenatal testing (NIPT)
- Analyse fetal DNA in maternal blood using NGS for vhromo. abnormality
b) more Sn than traditional markers (BUT $$$)
What is gestational diabetes mellitus (GDM)
Development of diabetes during pregnancy. Bc at pregnancy:
- mum on insulin resistant state i.e. not respond normally to insulin
- lrg fluctuations in plasma glucose in fast/fed states
What are the risk factors for GDM? (7)
- Age 40+ y.o.
- Family Hx w/ type II diabetes or gestational diabetes
- prev. Hx or had a baby >4.5kg
- Overweight
- have PCOS
- Ethnicity: e.g. African, Asian
- Drugs e.g. glucocorticoids = inc gluc.
what complications can arise in mothers with GDM and their offspring?
Mum: inc risk of mum developing diabetes later on
Baby: birthweight >4kg; inc risk of neonatal Hypoglycemia (bc their insulin working); perinatal mortality; preeclampsia (kidney damage)
how is GDM diagnosed?
- Mum tested24-28 weeks of preg.
- using modified OGTT aka POGTT (preg.)
- 2hr 75 OGTT
- result reported as % or mmol/mol (HbA1c per Hb)
what is the relevance of the term Multiple of Median (MoM)
a measure of normality for particular gestation age.
Multiple of median refers to *concentration of the biochemical *markers relative to the *median found in pregnant mothers with a foetus at the *same gestational age who have had successful pregnancies, i.e. producing healthy offspring
Nuchal translucency is done in the first trimester, what is it
- ultrasound
- measure thickness of subcutaneous fluid-filled space at bottome of baby’s neck
- If inc thickness = abnormal/delayed lymphatic drainage sys.
1st & 2nd trimester screening have 5% false pos.
a) What factor may have caused this?
b) Dx test for confirmation
a) frequently due to incorrect gestational age e.g. twins or poor foeatal health
b) Nuchal testing for 1x baby, biochem testing for twins
Dx tests for confirmation is invasive: amnioscentisis or chronic villi -> karyotyping & chromosomal studies
Method for measuring PAPPA, uE3, aFoeto protein (AFP), free B HCG
*uE3: steroid hormone = assayed w/ competitive/titrimetric assay or HPLS-MS / TMS/MS
*PAPPA, AFP, BHCG: immunometric or sandwich assay
