I absolutely did consider that. Did you consider that I might actually have looked into this reasonably seriously at one point? Like, say, when I was on my way to being a father?
The link that I provided explains the characteristics of the umbilical cord that have been evolved to minimize the probability of problems. It really isn't a problem. Even in childbirths where people don't worry about the umbilical cord.
This shouldn't come as a surprise. Evolution has selected for safe natural childbirth. Unfortunately in homo sapiens there is a conflict between our recent evolutionary pressure for large heads, the needs of walking, and for safety during childbirth. And so childbirth is much more dangerous for us than for other mammals.
Modern humans also have the problem of mothers in poor health. Reasons vary from drug use, to age, to sedentary lifestyles. Of these, drug use is the most dangerous. Despite most mothers not using drugs, drug use is a factor in something like half of childbirth deaths.
Then there is the list of usual complications. Breech birth, infection, blood type incompatibility, diabetes, heart attack and so on. It is a long list. It interacts with the previous lists - for example breech birth is made more dangerous because of our large heads. Complications from knotting of the umbilical cord is very far down the list of things that go wrong.