Body odour can be caused by poor hygiene and by medical conditions where puberty occurs too early with secretion of certain hormones. This latter cause has to be thoroughly investigated especially when care of body/skin is not an issue. Any child less than 4years should not have body odour. Such a child has to be examined by a paediatric endocrinologist as soon as possible. The cure or treatment is dependent on the cause. the odour is reversible if its due to poor hygiene.

It is not necessary to give new borns bath twice daily, once a day is okay. Moreover new borns needs to be kept warm as much as possible.

No, it's not necessary. Just bath the baby normal and also there's no need for twice a day bath.