Screening tests Flashcards
When is amniocentesis indicated?
Chromosomal abnormalities
DNA analysis for genetic disease (sickle cell, CF, muscular dystrophy)
Enzyme assays for errors of metabolism
Release intrauterine pressure in polyhydramnios
Rule out chorioamnionitis
Intraamniotic dye to confirm cases of PROM
How is amniocentesis carried out?
Remove amniotic fluid with a fine gauge needle under USS guidance
15-20ml sampled
Results for:
Aneuplodies within 48 hours
Full culture 7 - 10 days
Genetic disorders varied time
Safe to do from 15 weeks gestation
1% risk of miscarriage, risk of talipes if <15 weeks
How quick do results get back for amniocentesis?
Aneuplodies within 48 hours
Full culture 7 - 10 days
Genetic disorders varied time
When is amniocentesis safe to perform?
Safe to do from 15 weeks gestation
1% risk of miscarriage, risk of talipes if <15 weeks
Risks of amniocentesis?
1% risk of miscarriage, risk of talipes if <15 weeks
How is Chorionic villus sampling done?
Biopsy of trophoblast with fine gauge needle through abdominal wall under USS guidance or forceps/catheter through cervix into placenta
What does amniotic fluid contain (amniocentesis)?
Amniocytes
Fibroblasts
from fetal membranes
When can chorionic villus sampling happen?
From 11 weeks
Higher rate of miscarriage as performed earlier when early miscarriage is likely
Risk of fetal limb abnormality if <10 weeks
What can happen if chorionic villus sampling occurs?
Higher rate of miscarriage as performed earlier when early miscarriage is likely
Risk of fetal limb abnormality if <10 weeks
What happens if placental mosaicism is found in chorionic villus sampling?
Abnormality in one cell line but other cell line is normal = obtain another fetal tissue e.g. amniocentesis
What occurs at the booking visit?
Booking visit: 8 - 12 weeks
When women believes she is pregnant: information given by midwife
Measurements:
- Height
- Weight
- BMI
- BP
- Urine
Ask about domestic abuse, FGM and OBG history
When does the booking visit take place?
Booking visit: 8 - 12 weeks
When women believes she is pregnant: information given by midwife
What measurements are taken in the booking visit?
Measurements:
- Height
- Weight
- BMI
- BP
- Urine
Ask about domestic abuse, FGM and OBG history
What booking bloods are taken during the booking visit?
Bloods:
FBC, Cross match
ABO, Rhesus antibodies
Rubella
HIV
Syphilis
Haemoglobinopathies (SCD, thalassaemia)
Why is LMP not accurate for EDD calculations?
Assumed a 28 day cycle with ovulation at day 14
When is the dating scan done?
8 - 14 weeks
Calculate EDD using USS: Uses Crown rump length, accurate up to 13+6 weeks
How is Estimated Due date calculated during the dating scan?
Calculate EDD using USS: Uses Crown rump length, accurate up to 13+6 weeks
If a person presents with a late booking for pregnancy, past usual dating scan week range (8-14), how is EDD measured?
Use a head circumference rather than crown rump length for 14-20 weeks
USS becomes less accurate in later pregnancies.
As well as the dating scan in weeks 8-14, what other test is done?
Combined test (screening for down syndrome)
11-14 weeks
-> USS nuchal translucency +
-> bHCG
-> PAP-A
What is measured at the combined test at 11-14 weeks?
Combined test (screening for down syndrome)
11-14 weeks
-> USS nuchal translucency +
-> bHCG
-> PAP-A
What is the 20 weeks anomaly scan?
Review and discuss the results of screening tests, offer amniocentesis or Chorionic villus sampling if high risk: 1/150
Also offer whooping cough vaccine up to 32 weeks
What is considered as high risk genetic disorder?
1/150
Also offer whooping cough vaccine up to 32 weeks
What is the Quadruple test?
Offered at 14+2 weeks - when nuchal translucency was not obtained or 20+2 weeks for down syndrome when nuchal test is less accurate
What Anomaly scan occurs between weeks 18-20 and what for?
Anomaly US for 11 physical conditions:
- cleft lip
- anencephaly
- spina bifida
- diaphragmatic hernia
- gastroschisis
- exomphalos
- cardiac abnormalities
- renal agenesis
- skeletal dysplasia
- Edwards
- Patau
