So I asked this question today for the Ask a Vet radio show. Dr. Kanfer said there is absolutely no evidence in cats of long-term problems from early neutering, male or female. Now if you had a male sheep or goat, studies have shown that the urethra stops growing so THEY can end up with urinary trouble and blockages, so for male sheep and goats he asks people to hold off until they are 4 months old. But for cats, no long-term impact for males OR females, other than the positive outcome of the original point!