Antenatal and neonatal screening Flashcards
Define screening
The process of identifying apparently healthy people who may have an increased chance of a disease or condition
Information, further tests and treatment are then provided to reduce associated problems or complications
What are the wilson and jugner criteria for a screening programme?
- it is an important health problem
- the natural history of the condition is well understood
- there is a detectable early stage
- treatment at an early stage should be of more benefit than at a later stage
- there is a suitable test to identify the early stage
- the test is acceptable
- intervals for repeating the test should be determined
- there should be adequate service provision for the extra screening workload
- the risks - both physical and psychological - should be less than the benefits
- the costs should be balanced against the benefits
What are the antenatal screening programmes?
Mother - Sickle cell and Thalassemia - Infectious diseases screening - Diabetic eye screening
Fetus
- Down’s Edwards’ and Patau’s syndrome
- Fetal anomaly scan
What are the neonatal screening programmes?
- Newborn infant physical examination
- hearing screen
- blood spot
Who are screened for sickle cell and thalassaemia?
Both parents - to see if they are carriers
How are sickle cell and thalassaemia inherited?
recessive
If both parents are carriers of sickle cell or thalassaemia genes, what is the chance their baby will have it?
1 in 4
What are the complications of sickle cell disease?
stroke acute chest syndrome blindness bone damage priapism chronic organ damage
What is the cure for sickle cell disease?
Bone marrow transplant
From which part of the world are people at highest risk of sickle cell disease?
West Africans Afro-Caribbeans Mediterranean Asia Middle East
What are the main symptoms of sickle cell disease?
Symptoms of anaemia
Sickle cell crises - severe pain
What are the two main forms of thalassaemia?
Alpha and beta
What are alpha and beta thalassaemia?
hereditary disorders of reduced or absent synthesis of alpha or β globin chains respectively
How is thalassaemia major treated?
regular blood transfusions
iron chelation to prevent iron overload
What is the prognosis of alpha thalassaemia major?
usually fatal in utero due to hydrops fetalis
and haemolytic anaemia
- hydrops fetalis is abnormal accumulation of fluid in two or more fetal compartments, including ascites, pleural effusion, pericardial effusion, and skin edema
Are both parents tested for thalassaemia trait?
If the mother does have the trait, the father is then offered a test to see if he carries it, too
Which types of thalassaemia are screened for in pregnancy?
only beta, bot alpha as there are no good biological markers for detecting alpha thalassaemia CARRIERS
if the fetus develops hydrops fetalis, then can take a blood sample from the fetus to confirm whether the fetus has alpha thalassaemia
Who is offered sickle cell and thalassaemia screening and when?
All women in high risk trusts
Certain women after using family origin questionnaire
by 8-10 weeks
Biological father of the baby is tested if female partner is a carrier
What is used alongside the sickle cell and thalassaemia screening?
Family Origin Questionnaire assists laboratory to interpret results and request appropriate testing
What is offered to mother and father if they are screened and found to be carriers of sickle cell and thalas.
offered counselling and prenatal diagnosis by chorionic villous sampling (taking a sample from the placenta) by 12+0 weeks
Can have TOP for an affected fetus
if born affected - will have referral to a paediatric haematologist
What is the alternative to antenatal sickle cell and thalassaemia screening?
can wait as all babies tested for sickle and thalassaemia on blood spot testing
What are the types of beta thalassaemia?
- Normal: genotype β2/β2.
Slightly anaemic, clinically asymptomatic. - β thalassaemia intermedia (genotype -/βo or β+/β+): Anaemic (symptoms usually develop when the haemoglobin level remains below 7.0 g/dL), very low MCV and MCH; splenomegaly, variable bone changes, variable transfusion dependency.
- β thalassaemia major (genotype -o/-o): Severe haemolytic anaemia, chronic transfusion dependency.
What diseases are screened for in infectious diseases screening?
HIV
Hep B
Syphillis
When are infectious diseases screened for in pregnancy?
women in early pregnancy
unbooked women in labour
How are women who test positive for infectious disease treated?
- treatment
- MDT plan of care and neonatal alert process - a form that is filled to alert the MDT of the plan for the baby when born eg bloods or tests eg an USS of kidneys
How are babies born to hep B mothers treated?
Vaccination at these times:
- within 24 hours of birth
- 4, 8, 12 and 16 weeks
- 12 months
What happens to women who decline infectious diseases screening in early pregnancy?
Reofferred at 20 weeks
All unbooked women in labour must be offered
How is syphilis transmitted in pregnancy?
transplacentally at any stage
What can syphilis cause to the fetus?
miscarriage - eg hydrops fetalis
pre-term labour
stillbirth
congenital syphilis
What is congenital syphilis?
Early (first two years): rash including condylomata lata, vesiculobullous lesions snuffles - nasal discharge haemorrhagic rhinitis osteochondritis periostitis perioral fissures hepatosplenomegaly generalised lymphadenopathy glomerulonephritis neurological or ocular involvement, haemolysis thrombocytopenia
Late: arthritis of the knees Hutchinson's incisors mulberry molars high palatal arch deafness facial deformity - frontal bossing, short maxilla, protuberance of mandible, saddle nose deformity, sternoclavicular thickening neurological or gummatous involvement.
What is vertical trasmisssion?
Transmission of an infection from mother to fetus during pregnancy or childbirth
Which infections are transmitted vertically?
TORCH infections T – toxoplasmosis from Toxoplasma gondii O – other infections (see below) R – rubella C – cytomegalovirus H – herpes simplex virus-2
Other infections include: Parvovirus B19 Coxsackievirus Chickenpox (caused by varicella zoster virus) Chlamydia HIV Syphilis
What are the two types of vertical transmission?
Transplacental
During childbirth
What types of infection can be transmitted during childbirth?
- Blood borne infections eg Hep B and HIV , as the placental barrier is broken
- STIs
What factor is predictive of greater chance of getting hepatitis B as a fetus?
- higher viral load of mother: will known this from the maternal blood sample given at screening
Which genetic fetal anomalies are screened for
Down’s
Edwards
Patau
What genetic abnormality is Down’s?
T21
What genetic abnormality is Edwards?
T18
What genetic abnormality is Patau?
T13
Who is offered Downs, Edwards and Patau screening?
All women
When do we screen for Downs, Edwards and Patau ?
between 11+2 to 14+1 weeks (same as the booking scan times - as done in the booking scan)
How is Downs tested between 11+2 to 14+1 weeks ie at booking scan?
the Nuchal Combined test which is:
- Nuchal translucency
- Blood test - Serum levels of PAPP-A & Free Beta HCG (levels help to identify downs, edwards and patau)
Maternal age also inputted and crown-rump length is used to identify the gestational age to understand whether the scan is being done at the right time between 11+2 to 14+1 weeks and the concentration of the biochemistry markers depends on the gestational age of the fetus.
What happens in terms of downs testing when a pt misses their booking scan or not possible to measure nuchal translucency ?
Quadruple testing
When is quadruple testing for down’s done?
14+2 – 20+0
so if one day late for booking
Why might it not be possible to measure nuchal translucency?
- foetal position
- maternal obesity
Apart from the booking scan and the quadruple testing (for Down’s only), how can we test for Downs, Edwards and Patau?
Anatomy scan at 18+0 – 20+6 weeks for anatomical abnormalities of these syndromes
What anatomical abnormalities would you find on the anatomy scan for Down’s?
AVSD
Ventriculomegaly (brain)
Duodenal atresia
Neural tube defects
What is the main exception for doing booking scan testing for Down AND quadruple testing rather than one or the other?
Twin pregnancies
What conditions is Down’s syndrome associated with?
Epilepsy Childhood leukaemia Autism Thyroid disorders Heart conditions Problems with hearing and vision
What are the different types of genetic abnormalities that lead to Down’s?
Most are a trisomy (95%)
Some are a translocation - extra copy of the chromosome 21 is attached to another chromosome
Very few are mosaic - some cells have normal DNA and other’s don’t
How would you denote a male with trisomy 21?
47 XY
What defects will a fetus/baby with edwards have?
Severe learning disability
heart defects
problems with respiratory system, kidneys and digestive system
Most do not survive past their 1st birthday, very rarely they may survive to adulthood
What defects will a fetus with Patau have and what is the prognosis?
80% have congenital heart defects Holoprosencephaly - forebrain fails to develop into two hemispheres Midline facial defects Abdominal wall defects Urogenital malformations Abnormalities of hands and feet
Most will die before they are born, be stillbirth or die shortly after birth
What is the cut off risk for classifying a fetus as high risk for Downs, edwards and patau?
1 in 150
Less than this is low risk
Higher than this is high risk
What is the cut off risk for diagnostic testing for Down’s edwards and pataus
Only for high risk women 1 in1 50
What are the DIAGNOSTIC tests for Down’s
Chorionic villous sampling
Amnioscentesis
What is the difference between Chorionic villous sampling and Amnioscentesis and what are their adv and disadv
Chorionic villous sampling - Sample from the placenta
- can be mosaic - some cells represent cells of the baby and others do not represent the cells of the baby
- risk of miscarriage 2%
- done from 11-14 weeks, so provides early diagnosis and early termination
Amnioscentesis - sample of amniotic fluid which contains cells shed from the skin of the baby
- NOT done before 15 weeks, so 15+ weeks only
- risk of miscarriage 1%, can lead to pre-term delivery if done after 24 weeks
What does the quadruple test test for?
Down's syndrome only Is a blood test - Alpha Feto Protein - total Beta HCG - Oestriol - Inhibin A
What are the options for women with a high risk for downs?
- No further testing – await anomaly scan (not diagnostic)
- Non Invasive Prenatal Testing in private sector (screening)
- Invasive diagnostic test – CVS or Amniocentesis (carries 0.5 – 1% risk of miscarriage)
What is Non Invasive Prenatal Testing for down’s?
analyses fragments of fetal DNA in maternal blood
only available privately and not on nHS
Can give risk of T21, T13, T18 and fetal gender
Up to 99% detection rate
0.1% false positive rate - and because of this, it is not considered diagnostic and no one would terminate on the basis of this test, more provides reassurance if negative. Reason is that some of the placenta may have genetically abnormal cells but this does not represent the cells of the fetus (placental mosaicism)
What is the purpose of the booking scan in general?
Confirm viability
Ascertain if it is a singleton or multiple pregnancy
Estimate gestational age
Detect major structural anomalies that may be identified in early pregnancy, e.g. anencephaly
Screening for down’s edwards and patau
What is the purpose of the anatomy scan in general?
to identify major abnormalities which indicate the baby may die shortly after birth
to identify conditions that may benefit from treatment before birth
to optimise treatment after the baby is born
to plan delivery in an appropriate hospital/centre
to provide choices for the woman and her family about continuance or termination of the pregnancy
To revise again: when are the dating and anatomy scans done?
Dating: 11+2 - 14+1 weeks
Anatomy: 18+0 – 20+6
How often are diabetic women screened for diabetic retinopathy?
at least twice during the pregnancy - all diabetic women are offered this
What scan do diabetic women get before the booking scan?
viability scan
WHo is offered diabetic eye screening?
existing diabetics who become pregnant
When is newborn examination done and where?
- within 72 hours of birth - At hospital or in community by midwife
- at 6-8 weeks - done by GPs
What is examined during the newborn exmainations?
eyes - cataract
heart - murmurs
hips - developmental dysplasia of the hip
testes - undescended testes
What are the neonatal screening tests?
- eyes, heart, hips, testes
- hearing loss
- blood spot
What conditions does the blood spot screen for?
- sickle cell disease
- CF
- congenital hypothyroidism
- inherited metabolic diseases
o Phenylketonuria (PKU)
o Medium-chain acyl-CoA dehydrogenase deficiency (MCADD)
o Maple syrup urine disease (MSUD)
o Isovaleric acidaemia (IVA)
o Glutaric aciduria type 1 (GA1)
o Homocystinuria (HCU)
