Thread support in cygwin!

Hi, I'm trying to port a program used pthread in Linux to Windows.In cygwin, I compiled it but when executing I got this message : Threads are not supported
In Linux, it works fine.
Then in Cygwin I write this simple program :

#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
int main()
{
#ifdef _POSIX_THREADS
        printf("sysconf(_SC_THREADS): %d\n", sysconf(_SC_THREADS));
#else
        printf("_POSIX_THREADS not defined\n");
#endif
        return 0;
}

And I get :
sysconf(_SC_THREADS): -1

Is that mean cygwin doesn't support threads? Or I missed some package?