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Thalassaemia Screening in the Pregnancy Booking Clinic
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- Couples attending the Royal Women's Hospital for antenatal care should be offered screening for haemoglobinopathies at the Pregnancy Booking Clinic.
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- All results are reviewed in Thalassaemia Clinic and where appropriate, appointments to the clinic sent with a covering letter indicating the possibility of thalassaemia and requesting partner screening.
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General information
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- Thalassaemia is an inherited condition that affects the production of haemoglobin, which carries oxygen in our blood. It appears in two forms:
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| carrier form - one member of the gene pair is not working properly
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| | | both members of the gene pair are not working
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| | | both members of the gene pair are not working
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- Thalassaemia may occur in people of any origin, however it is more common in people from certain regions.
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- Haemoglobinopathies are other abnormalities of haemoglobin that may interact with Thalassaemia or that may cause anaemia or episodes of severe pain.
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- The aim of the Thalassaemia Clinic is to identify couples in which both partners have thalassaemia minor and/or a haemoglobinopathy. Such couples are at risk of having a baby with serious disease. As prenatal diagnosis takes many weeks, it is vital to identify at-risk couples as early as possible in pregnancy.
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The significance of particular haemoglobinopathies and their potential interaction in pregnancy is a complex subject that lies outside the normal range of practice for many obstetricians, midwives and general practitioners.
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For this reason, it is strongly recommended that all patients with a documented haemoglobinopathy who are pregnant or considering pregnancy be referred to the Thalassaemia Clinic for appropriate investigation, treatment and genetic counselling, even if the partner testing appears normal.
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Patients of child-bearing age from at-risk groups should also be identified and screened when attending other clinics, particularly those involved with termination of pregnancy, family planning and reproductive biology.
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Patients may also be directly referred by hospital midwives or medical staff. Referrals from outside practitioners and patient self-referrals are also accepted.
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The Thalassaemia Clinic
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The Women's Thalassaemia Clinic is a multidisciplinary clinic that provides:
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- Genetic counselling for patients and partners;
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- Screening of partners and family members;
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- Diagnosis of pregnancies at risk of Thalassaemia / Haemoglobinopathies;
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- Coordination and genetic counselling for prenatal diagnosis.
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Couples at risk of infants with thalassaemia disease or severe haemoglobinopathy syndrome are referred to the Maternal Fetal Medicine (MFM) team for pregnancy management, including prenatal diagnosis.
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Mothers with thalassaemia disease or severe haemoglobinopathy syndromes are referred to the MFM Obstetrician attached to the Thalassaemia Clinic for pregnancy care.
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Consultation regarding Thalassaemia and the haemoglobinopathies is available at the Royal Women's Hospital through:
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| | | Tel: (03) 9345 5910 (pager 5828)
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Investigations
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Full Blood Examination alone is insufficient as a screening test.
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Testing for thalassaemia and abnormal haemoglobins requires:
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- haemoglobin electrophoresis.
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- If these results are suggestive of alpha thalassaemia:
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- DNA analysis is indicated.
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Screening of at risk patients (from high risk ethnic group, past history of anaemia, or family history of haemoglobinopathy) should occur prior to pregnancy.
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Prenatal diagnosis cannot be offered to at-risk couples unless DNA analysis has been performed and the exact nature of mutations has been determined.
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If the patient is iron deficient, screening should be repeated after iron stores have been replaced, as iron deficiency may result in an abnormal HbA2 in mild forms of beta thalassaemia minor.
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Partner screening in all cases where an abnormality is identified. Partner screening should be performed in all patients who are pregnant and iron deficient, as DNA studies may be required to determine thalassaemia risk if the partner demonstrates an abnormality.
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FBE findings in Thalassaemia and abnormal haemoglobins:
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| Potentially serious haemoglobinopathies for which prenatal diagnosis may be offered:
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MCV/MCH reduced +/- anaemia
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| Often normal red cell indices
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| Homozygous beta thalassaemia
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| Homozygous Hbs (sickle cell disease)
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| | | | Barts Hydrops (4 gene deletion alpha thalassaemia)
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| | | Haemoglobin H disease Hydrops (2 gene deletion plus point mutation)
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| | deltabeta thalassaemia minor
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| | Hb Lepore/beta thalassaemia
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| | Heterozygous Hb Lepore
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| | Hb O Arab/beta thalassaemia
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| | Some couples may request prenatal diagnosis for HbH disease (3 gene deletion alpha thalassaemia).
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| Rare variant haemoglobins
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Specific considerations
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- Pregnant women in whom beta thalassaemia minor is identified should receive high dose folic acid (5mg daily) throughout pregnancy as there is some evidence that this is beneficial in optimising haemoglobin levels.
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- Iron supplements should NOT be given in the absence of documented iron deficiency. Many patients with thalassaemia minor have a mild degree of iron overload and iron supplements do not improve haemoglobin or red cell indices unless iron deficiency is present.
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Further information
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Haemoglobinopathies (comprising the thalassaemias and abnormal haemoglobins) are hereditary disorders which affect the balance of globin chain synthesis and/or the structure of haemoglobin.
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These disorders are detected in approximately 4% of patients of reproductive age attending the Royal Women's Hospital. In almost half of these cases, the abnormality is not evident following simple full blood examination and is only detected by haemoglobin electrophoresis.
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Thalassaemias and abnormal haemoglobins have been described in every ethnic group. They are most frequent in people originating from:
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As the inheritance of thalassaemia syndromes is autosomal recessive, the heterozygous carrier states are essentially asymptomatic. Most people are unaware of their carrier state.
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Depending on the mutation, homozygous or compound heterozygous thalassaemia syndromes may result in adverse maternal outcomes, stillbirth, transfusion dependency, or sickling syndromes.
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The aim of screening couples for thalassaemia is to detect those at risk of having children with severe disease, with a view to offering prenatal diagnosis and the option of termination of pregnancy in the event of a positive diagnosis.
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Identification of at-risk couples allows for appropriate antenatal care of women with the potential to deliver a baby with Bart's Hydrops and early follow up of affected children, regardless of whether prenatal diagnosis is performed.
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Detailed genetic counselling and family studies are important for future pregnancies.
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Please remember to read our disclaimer.
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