I'm breastfeeding my 8mnth baby her weight is 7.700 kg. I have migraine so I need to take topiramate. Is my baby at risk if I use it?

Yes, extent unknown. Topiramate causes birth defects and growth retardation in exposed fetuses. You do not "have" to take topiramate to prevent migraine. 10% or more of your dose of topiramate is expressed in breast milk. No one can assure you that this is ok for your infant, whose brain is now growing at the highest rate. No information exists about potential increased risk of s autism or other problems.