What causes double aortic arch in babies?

Q: I am a 26 year old lady and was blessed with a son. At the time of birth his weight was 3.5 kgs and he was normal. With time I observed that he had a breathing problem which became more just after feeding. I contacted a doctor and finally the problem detected was double aortic arch which was compressing his breathing as well as feeding pipes. As per the doctor its remedy was surgery and he was operated and his recovery was fine. He was taking my milk but two days later during feeding he became blue and the doctor stopped mouth feeding saying he would investigate the problem. At mid-night bleeding started from the nose and he finally collapsed due to excessive bleeding. As per doctor it was totally unexpected and he did not explain to me the reason of death but guessed that the reason was haemorrhage of lung! May I know what may be the reason of his death? May I also know the reason behind the cause of double aortic arch. During pregnancy I had a positive toxoplasma test and I was treated for it but in last month of pregnency it was ok. Could this be the problem? My mother had heart problem but I am do not have any heart related problem. My husband smokes. Can this cause a double aortic arch as he assumes?What is the probability of the same in the next pregnancy and how can it be controlled during pregnency? Being a mother I am afraid and I spent around Rs. 1.5 lakh to treat my son but the result was sad. So advise me and I will be obliged to you. My question is too long but I hope I will be excused.

A:Obviously this problem is related to a complication of surgery and is unfortunate. We really do not know the cause of Double aortic arch. During development of the arch in the foetus, the arch is always duplicate and one of them regresses. This has failed to occur. I am not aware of any relation to smoking or positive toxoplasma results and these are so difficult to prove. There is association between Double aortic arch and 22q 11 deletion in chromosome but we are far from understanding why these deletions occur. It is suggested that both parents should have tests for asymptomatic chromosome deletion and this is something that Dr. I. C. Verma may be able to guide. If any of the parents are positive for deletion, then there is 50% chance that the next sibling may have cardiac problems related to q11 deletion. If the parents are negative then we would consider this as a mutation and then the chances are less (although not zero) for the next sibling to have a congenital heart disease. Many of these can however be detected by expert fetal echocardiographer early in pregnancy and appropriate counselling be performed.