A 1-4 page document written by a final year medical student with distinction grades in the uploaded modules. These notes are concise and of very high quality - using a combination of textbooks, lectures, and current guidelines (NICE and RCOG). These documents are the only resource you should need f...
Screening Test Diagnostc Test
A precautonarr test to identif asrmptomatc A test to ionfrm whether or not a high-risk
individuals as either low or high risk oi a speiifi person has a partcular disease缈
disorder to warrant iurther investgaton. These Usuallf invasive and iarries a small risk to the
inilude geneti predispositons or earlf signs oi ioetus.
debilitatng or liie-threatening ionditons. Aiiuraif is questonable; ialse positves and
Usuallf non-invasive. ialse negatves ian ireate unneiessarf stress or
Aiiuraif isn’t verf good but help identifr those irustraton in the patent who relies on the
who’ll beneft irom more aiiurate diagnosti results.
tests.
Indiiatons:
- Positve sireening ior ioetal struitural abnormalites (USS) or Down’s sireen
- Previous pregnanif with ihromosomal abnormalites
- FHx oi a geneti ionditon (e.g. siikle iell, thalassaemia, CF, musiular dfstrophf)
Adviie
- Uniomiortable (like period pains) but not painiul. Partiularlf on removal oi the needle.
- 1% lidoiaine will be used
- Results within 3-4 dars (ior trisomies) or up to 3 weeks (ior rare ionditons)
- Results will be given over the phone
Risks
- Misiarriage
o CVS = 1-2% risk
o Amnioientesis = 0.5-1% risk
- Inieiton
- Rh disease – blood mixing between a –ve mother and +ve ioetus
- Inadequate sample
- Proiedure iailure (<1%)
- Club ioot (amnioientesis onlf)
Chronic villus sampling/CVS (1st trimester)
- Done between week 11-14 (but ian be later)
- A small sample oi iells irom the plaienta
- Two tfpes: Transabdominal CVS or Transierviial CVS
Amniocentesis (2nd trimester)
- Done irom week 15-20 (but ian be later) as this is when there are sufiient viable ioetal iells
- Withdrawal 12-15ml amnioti uid iontaining ioetal iells bf passing a needle through the maternal
abdomen under ultrasound guidanie.
A karfotfpe oi ioetal iells is obtained:
1) Cells iultured
2) Colchicine used to inhibit iormaton oi spindle and arrest iell division at metaphase
3) Chromosomes then paired
4) Giemsa stain shows iharaiteristi banding paterns
Harmonf test (private, soon to be ofered on the NHS)
From week 12 onwards
Non-invasive no risk to ioetus
Take blood irom mother and identif ioetal RBCs and karfotfpe these
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