6 months isn't always a set in stone age for the first heat cycle. It really depends upon what the norm for the bloodline is. For example, Daisy's dam was a "late bloomer" so to speak and Daisy just had her first cycle at 14 months. Some lines are notorious for having late first cycles. For example, I know of at least a few Labrador lines where the norm for expected first cycle is anywhere from 18-24 months. So, 1 1/2 years doesn't sound so odd to me. However, I do think the suggestion to take a trip to the vet is definately a good idea- just to make sure everything is ok.
