1998 Honda Accord slipping during shifting

I have a 98 Honda Accord with 2.3 vetc. The problem I am having is with the transmission. It slips shifting from 1st to 2nd, (about a 1 to 2 hundred) tach increase during the shift transition (say about 3 second’s period). It does it going from 2nd to 3rd also but it is less noticeable.
It also doesn’t do after five minutes of driving.
Any idea of what is wrong.

Mike Kaniclides

I changed the fluid after the problem started It is at the correct level. Also no problems with old fluid.