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What precautions should we take before planning a child if my Hb A2 is raised?

Q: I am a 28 years old female weighing 55 kg. My HbA2 level is slightly high i.e. 3.6, but other factors like HbF are in the normal range. There is a history of thalassaemia in my husband’s family. What precautions should we take before planning a child?

A:Thalassemias are a group of genetic diseases caused by the production of abnormal hemoglobin, the red coloured protein present in red blood cells that transports oxygen in the body. Haemoglobin comprises two beta - globin and two alpha - globin chains, their production being governed by 2 beta and 4 alpha genes respectively. In alpha-thalassaemia, the production of alpha - chain is abnormal while in beta - thal it is the beta - chain. When only one beta - globin gene is affected (thal minor or trait or carrier or heterozygous), it results in mild anaemia not requiring treatment but the involvement of both genes results in severe disease (thalassaemia major or intermedia) requiring regular treatment and follow-up from infancy.

An adult normally has the following types of haemoglobins (Hb) present in blood:

Hb A – made up of 2 alpha and 2 beta globin chains : 95% of total
Hb A2 – made up of 2 alpha and 2 delta globin chains : 3% of total
Hb F – made up of 2 alpha and 2 gamma globin chains : 2% of total

The normal Hb A2 level in an adult is less than 3.5% and it is elevated (>4%) in ? thalassaemia trait. Beta thalassaemia trait is a clinically benign disorder. The importance lies in the fact that if both parents are carriers (i.e. carry one abnormal beta - gene), an offspring may co-inherit a beta -thalassaemia gene from both the parents making it homozygous resulting in a medically significant thalassaemia (beta - thalassaemia major). Hb A2 values between 3.6-4.0% are in the indeterminate range i.e. they may be of no clinical significance or may imply rare carriers. There are very rare instances where a thal carrier may have normal Hb A2 level and such cases can be detected only by DNA analysis (so called Silent or near silent?? -thalassaemia trait).

Please discuss with a haematologist and get your husband tested and if he is normal, there is no problem.

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