As others have said, there are pros and cons.
Yes, if you allow the bitch to have even one season, you increase the risk of cancers dramatically. On the other side the risk of "spay incontinence" is increased if you spay before first season - there is also some evidence that some bitches who are spayed early can fail to mature as well and remain slightly puppy-like (though I thought all spaniels were like this anyway!!!

). There are lots of articles on the web (Pro and Anti early spays) which got into far more detail about the risks and benefits of each - I found them doing a Google search for "bitch spay 6 months" I think.... bear in mind all are written with an agenda, so the Pro ones focus on the risks of having seasons and the Anti the risks of not!!
We decided to spay Honey before her first season. The health factors played a big part, but there were also practical issues to consider - I could book a week off work to stay with her after her spay, so that the fact that she was limited to on-lead gentle exercise wouldn't be an issue, whereas there is no way we could have planned any time off to ensure she got adequate exercise during her season. We live close to many dogs, and the only places we know to walk are used by many, many dog walkers... I think she would have been climbing the walls with the restrictions having a season would have placed on her. While this was not the over-riding factor in making the decision, it did have its place in the considerations.
