Hello,
as far as I know fragmentation is managed at the IP level in the IPv4 header/ IPv6 header.
In the TCP header there are some fields like the urgent pointer but they are not related to IP fragmentation.
See http://www.wtcs.org/snmp4tpc/images/TCP-Header.jpg
So the answer is that it is IP not UDP or TCP that deal with fragmentation.
hope to help
Giuseppe