Genetics, Pregnancy and Child Health Flashcards
What can all pregnant women be screened for at 11 weeks gestation?
Down’s syndrome
What is needed to do DNA/chromosome testing on a baby in utero?
Tissue with the same genetic make up = placenta (chorionic villus biopsy), skin/urine cells (amniocentesis)
When can DNA/chromosome testing be done?
CVS = at 11.5 weeks Amniocentesis = at 15+ weeks
What is sampled in non-invasive prenatal testing?
Free foetal DNA in maternal circulation (only 10% comes from foetus)
What can non-invasive prenatal testing be used for?
Trisomy testing and sex determination
Does amniocentesis carry any risks?
Yes = 1% chance of causing miscarriage
What is confined placental mosaicism?
When the placenta carries a genetic difference that the foetus doesn’t carry (e.g placenta may have chromosome trisomy that is absent in foetus)
What kind of result in non-invasive prenatal testing would indicate foetal Down’s syndrome?
Slight excess in chromosome 21 in maternal serum
Why is screening during pregnancy deemed acceptable?
Allows early recognition, gives parents time to adjust to diagnosis before birth, patients consider it a part of their healthcare service
How is termination of pregnancy carried out?
Surgical termination before 13 weeks
Induction of pregnancy thereafter
In what scenarios would their be no time limit on getting a termination of pregnancy?
If there is risk of serious abnormality in the child or to the health of the mother
What causes Edward’s syndrome?
Trisomy of chromosome 18 = poor prognosis, often born premature, very small size and cardiac defects
What are some influences that may cause parents to decide to get a termination of pregnancy?
Social and religious views, previous experience, perception of disease
Are terminations of pregnancy usually seen in wanted or unwanted pregnancy?
Usually for a wanted pregnancy
How does known haemophilia in a foetus impact their future management?
More foetal blood tests requested to confirm diagnosis
Vitamin K isn’t given via IM injection
What is invasive testing used to identify, and what methods are used?
Single gene changes = PCR, next generation sequencing
Chromosome abnormalities = chromosomal microarray
What does aCGH identify?
How much DNA a person has (i.e how much of a certain chromosome is present)
What are the benefits and issues with chromosome microarray?
Benefit = high resolution, rapid, technically easier Issues = also finds polymorphisms, may make incidental findings
What are some indications for invasive testing?
High risk of chromosomal trisomy on screening
Positive non-invasive test results
Foetal abnormality on scanning
If parent has balanced chromosome rearrangement
What are some foetal abnormalities seen on scanning that may need further invasive testing?
Small size, increased nuchal thickness, malformations
What are some features of a floppy baby?
Like a rag doll, lack of head control, increased ROM, frog legged, possible breathing difficulties
What are some locations that may be affected to cause floppiness in a baby?
Cortex, spinal cord, anterior rami/motor neurons, neuromuscular junction, muscle
What site is most commonly implicated in causing floppiness
Central causes (i.e brain)
How many polymorphisms do most people have?
3 million
What kind of mutation is implicated in a significant proportion of severe presentations in neonates?
De novo mutations
