Birth Flashcards
What percentage of all pregnancies ends in miscarriage?
50%
What is the most common cause of miscarriage?
Chromosomal abnormality
How many babies at term have a chromosomal abnormality?
1/250
What are the three types of chromosomal abnormalities?
- Aneuploidy
- Rearrangement
- Deletions or duplications
What is aneuploidy?
Too many or too few chromosomes
What are three types of chromosomal rearrangements?
- translocation
- inversioin
- complex chromosome rearrangement
What are two common causes of aneuploidies?
- Malsegregation
2. Raised maternal age
When does Malsegregation of chromosomes happen?
- In gonad during meiosis —> abnormal gamete
- During mitosis in the germline —> mosaicism in the gonad
- During mitosis in the early embryo —> mosaicism in the embryo
What are the two types of chromosomal translocations?
- Robertsonian
2. Reciprocal
What happens in Robertsonian translocation?
Two chromosomes halves fuse two form one
What is the most common Robertsonian translocation?
Chromosome 13 and 14
What is the prognosis for Robertsonian translocation?
Phenotypically normal, may have increased reproductive risk
What is reciprocal translocation?
Two chromosomes exchange halves (total number of chromosomes normal)
What is the prognosis of reciprocal translocation?
Phenotypically normal
What is the prevalence of T21?
1/800
0.12%
What is Edwards syndrome?T
T18
What is Patau syndrome?
T13
What is Turner’s syndrome?
45, X
What is Klinefelter syndrome?
47, XXY
What are three types of monogenetic disorders?
- Spinal muscular atrophy
- Cystic Fibrosis
- Duchenne muscular dystrophy
What is genetic testing?
sample from the pregnancy for the presence of specific disorders (invasive)
What is genetic prenatal screening?
produces a risk figure for the fetus of having certain abnormalities, this is NOT a diagnosis
What does QF-PCR detect?
Aneuplodies
What do array comparative genomic hybridisation tests detect?
Genomic imbalance across genome
T13, T18, T21
What is FISH used for?
to detect unbalanced products of a known familial unbalanced rearrangement
What invasive testing tools can be employed?
- Chronic villus sampling
- Amniotic fluid sampling
- Fetal blood sampling
What non-invasive testing tools can be employed?
Peripheral maternal blood sampling
What is a normal order of prenatal testing (tools)?
Samples from amniotic fluid, chronic villus fluid or fetal blood
QF-PCR for trisomy
FISH for unbalanced products of the rearrangement
What prenatal tests are routine?
Infectious disease
Screening for T21, T18, T13
What is a combined prenatal test to detect trisomies?
- Maternal age
- Measurement of nuchal translucency
- Gestational age from the length of the fetus
- Level of two hormones (PAPP-A and B-hCG) in maternal blood
When can a combined prenatal test be carried out?
10-14 weeks
When can a quadruple test be carried out?
14-22 weeks
What does a quadruple test measure?
AFP, hCG, unconjugated estriol, inhibin A
What can the 20 week anomaly scan detect?
Patau, Edwards, Downs
What percentage of Down fetuses will not be detected?
10-20%
What three genetic tests are available?
- testing for a singular gene disorder
- Parental chromosome arrangement
- Genome testing following the detection of fetal abnormality