Introducing a single Unicode character in an SMS message changes the character encoding to Unicode (UCS-2) and reduces the segment character limit from 160 to 70 characters for a single message. When messages with Unicode characters are stitched together, three characters are sacrificed per segment.
Therefore:
2 message segments with Unicode: 67+67=134 characters
3 message segments with Unicode: 67+67+67=201 characters
etc.