Kava Tea and breastfeeding and / or pregnancy do not mix. It is not advised to drink kava while breastfeeding as the effects of kava will be passed through your breast milk to your baby.
Kava is known to create several 'feel good' symptoms, and to relieve stress, however I am not confident to say it is okay for your baby.
You may want to discuss this with your medical doctor or herbalist. My opinion is to not mix breast feeding with kava.
Hope this helps, and please do seek some professional advice on the matter and let us all know what you have been able to find out.