The quantity or frequency of the transfusion depends on some factors like body weight, activity level of the child and overall general health of the child. The HB tends to fall faster for very active child or in case of general illness like cough, cold, fever etc. Usually the amount required for transfusion is decided on body weight - the rule is 12 - 15 ml/ kg of body weight. Initially when the baby is small and activity levels are low, the frequency and quantity of transfusion will be lesser. As the baby grows and gains body weight, the quantity of blood required during each transfusion will go up. For every KG of body weight gain, the quantity of blood transfused will go up by 15 ml.
For the first 2-3 years, your frequency of visit to the hospital for transfusion may remain low at one visit in 4-6 weeks as it is the quantity of blood required that will go up and not how frequently the child is transfused. The frequency of transfusion will stabilize between once in 4 - 5 weeks as the child grows further and the activity level goes up, say for the next 3-6 years.
Once the child attains a body weight of 25 - 30 kgs, the frequency of visit to hospital possibly would be between once in 3- 4 weeks. By that time the child possibly would be 10 - 12 years old.