而这可能也是为什么脐带很少打结的原因（在新生儿中仅有1%的发生几率）：母亲的子宫空间太小了，脐带难以互相缠绕。
This has been proposed as the reason why umbilical cord knots are rare ( happening in about 1 percent of births ): The womb is too small to allow for the organ to tangle around itself .
脐带打结