Honestly, I don’t want to encourage where you should fast or not. I breastfed mine and I felt weak and my supply dipped. My 13 month old ate at that time so I was really concerned. If you are planning to fast , there is an electrolyte supplement you could mix with your water. It’s called iv fluids.
I tired a liquid fast the 1st day and it was a no go.
Fasting is not mandatory for pregnant, postpartum and breastfeeding mothers. If you even fear harm to the baby or yourself that’s enough to exclude you. Allah knows our struggles and also our intentions
I believe it's completely up to you and how you feel you'll be if you don't eat for hours. Only you will know if it's affecting yourself and/or your baby so assessing that will in shaa allah help make your decision.