Her baby is 20% breastfed; can she not fast?
Question

My baby is about one month old and is only 20% breastfed because my milk is very little; the rest of what he needs is given by means of artificial milk. I am living in a country where the hours of fasting are approximately seventeen hours. What is the ruling on fasting in my case?
Praise be to Allah.I put this question to our shaykh, ‘Abd ar-Rahmaan al-Barraak (may Allah preserve him) and he said:
She may break the fast and make it up on short days. End quote. 
Please see also the answer to question no. 49794 
And Allah knows best.