I'm horrified to see 2 people have already made arrangements to neuter their 4 month old kittens. What the? Why can't people let the kittens be kittens, bloody hell at that age they haven't even got their adult teeth! I know females can come in season early, but generally at 6 months and they also tend to come in season in Spring to early Summer. All it takes is a little common sense, no one could mistake a female in season .. if you get caught out keep them in.
I think far more research has been done on dogs but I'm sure you are aware there is a much greater risk of bone abnormalities, cruciate damage and some cancers in dogs neutered before maturity. Simply they need the sex hormones to close the growth plates. Personally I would never do it and leave my boy cats till 6 even 7 months. Some of the issues with early neutering in dogs are becoming apparent in cats, some of the cancers and behavioural problems, though of course vets will never admit to that! At 4 months old they are still very much babies and even Freshfields still recommend 6 months for both sexes.
Of course people need to neuter cats, there is no doubting that fact.Tthe situation in North Wales alone is dire. Responsible cat ownership must include neutering, but at a sensible age. I believe dogs can be and should be left till a minimum of 2 years old but with cats it's different, a different species a different life style, but the thought of getting Luther neutered now makes me shudder. Bloody American vets, this all started there and as ever the British don't think for themselves and consider the consequences of their actions!