Will slapadd work with delta-syncrepl?

I have set up delta-syncrepl between provider A and consumer B, and it seems
to work ok. Online updates to A are synch'ed to B. However, about once a
month, there is a large update which contains hundreds of million records.
Online update is going to take days. I tried to bring A offline, do
slapdadd, and bring A back online. But these new entries were not synch'ed
to B. Is there a way I can make this work?

Thanks,
Khoa