Question
I read on multiple sites about how to help a queen give birth to her kittens, and almost all of them say that the cat usually chews the umbilical cord, but if she doesn't, then you have to do it. But instead of just snipping it, they want you to tie thread on either side of it. I am completely blind, and without some means to envision what is actually going on, it is very hard for me to imagine why using a thread would be necessary when I could simply feel between the kitten's body and end of the cord and snip in between.
Besides, if you tied the thread to either side of the cord and then snipped the cord, the thread (if not snipped) would hold the severed cord, and it might also pose a danger to the queen.
Here's an example of one of these articles.
Answer
Saliva contains coagulants, so the mother chewing on the cord and licking the stump will help the blood clot, while cutting it with a blade would not clot naturally until a large amount of blood escaped—perhaps a fatal amount.
Tying the umbilical closed with a thread at the navel end will stop circulation to/from the kitten's body so you can safely cut the umbilical. Platelets will accumulate there and clot, and the umbilical stump will soon die (from lack of oxygen and nutrients) and fall off the kitten. If you tie off the placenta end too, it would be a second thread just to keep the blood in the placenta from draining out before you disposed of it.
The thread itself should be as thin as will do the job and any excess trimmed after tying the knot, so if it does end up getting eaten by the kitten or queen, it should pass through their digestive system without causing any problems.
When human babies are born in hospitals, doctors use sterile metal clamps instead of threads, but the basic idea is exactly the same.
Answered By - StephenS