Birth weight does not indicate the kitten's sex or future development. Many times the smallest kitten at birth "catches up". As a breeder I can only tell the color and pattern of the kitten a few hours after its birth. Before the kitten begins nursing I check the nose to make certain it is straight because once it has begun nursing the nose gets "crunched" into what I call a "nipple nose". It is also the best time to try to determine the sex of the kitten (my ability in this category is about 60% accurate). If I miss being able to sex the kitten at birth I need to wait until it is 3-4 weeks old before I know for certain. Other than these indicators, birthing time is a time for the kitten to eat, sleep, eat, sleep. The kittens change greatly from day to day, and the Norwegian Forest Cat Dams are very attentive and protective. The Dams gradually put their kittens on a nursing schedule beginning from constant nursing to more regulated nursing periods. Dams go into heat about 10 days from birth, then again in 30 days and then right back into their cycles. I prevent my Dams from any opportunity to breed during these times.
At the age of about 3 months the kittens have developed into little furballs with fat tummies. At this age there are considerable differences in weight of the kittens. Male kittens may not have yet outgrown their sisters, and usually there is one of the kittens who still thinks his mother's milk is the best food in the world. At this age the kittens usually look in balance or harmonious and well proportioned, but this is not to remain so. Somewhere between 4-6 months old the kitten body suddenly beings to grow but not in unison. The body may grow long or the legs get their spurt of growth. The ears may look like they belong on a bat instead of a cat. One glorious morning the lengthening tail may reach all the way to the nose. It is a time of rapid growth of the various parts and often results in humorous looking kittens. It is only a stage of kitten development.
At about 10-12 months the kitten body once more becomes proportioned in its parts. It is now possible to form an idea of what the adult cat is going to look like. From this period up to adulthood the changes become much more gradual and subtle. The Wegie is not fully matured until it is about 4-5 years old, females maturing a bit earlier. Not until mature will the cat reach its maximum adult weight. The Wegie is one of the breed which has the greatest difference in size between male and female. The females are often elegant creatures of 8-11 pounds whereas a fully grown male usually weighs between 12-17 pounds. Neutered cats will get a little bigger and carry a bit more weight.
There are some who say that a Wegie should not be neutered because it will not grow to the right size or develop the correct coat. The fact of the matter is that neutered Wegies often become larger than their fertile counterparts. Moreover, the neutered Wegie gets a thicker and more beautiful coat. There are many relatively new statistics indicating early spaying or neutering does not damage the cats'; growth. I suggest you discuss this with your veterinarian and weigh the pluses and minuses. Suffice to say that females and males need to spayed or neutered when they reach sexual maturity. In the Norwegian Forest Cat breed that time can be anywhere between 10 months to 2 years, depending upon the lines the kittens are coming from. It is a slow developing breed most usually. Again you should discuss this with your vet and breeder as the breeder knows the bloodlines.
The Development from Kittens to Adults