FACT: If you are allowed to submit opening pages along with your email query pitch letter, including the prologue pages will kill your query 99.9% of the time and agents won’t ask for sample pages.
–Kristin Nelson’s #NLAquerytip #7.
Kristin goes on to explain why, but it’s basically because the tone tends to be so much different to the rest of the novel. If you’re querying an MS with a prologue, best to leave it off and start with your actual Chapter 1 for your sample pages.
That being said, I submitted Liesmith‘s prologue to Sara–who worked for Kristin at the time–and she forgave me for my sins. So… yeah. There are no rules, only guidelines, and all that.