All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The scholars stated that a person taking a means (to achieve something) which Allaah did not legislate nor decree it to be a means of achieving such an objective, is considered a type of minor Shirk [associating partners to Allaah]. Therefore, believing that a pregnant woman who uses a knife, when there is an eclipse will cause harm, is considered Shirk because using the knife is not a reason of being harmed and this is neither legislated nor decreed, and neither in eclipse nor at other times.
Also, saying that the cat's crying - if we suppose that a cat cries - or the weeping of a person causes harm, is seeing an evil omen, and it is confirmed that the Prophet said: "Seeing an evil omen is Shirk." [Ahmad] Likewise, wearing a black string in order to protect oneself from evil eye or from the harm of the people or the Jinn is considered Shirk. If one believes that it can harm by itself, then this is a major Shirk, and if one believes that it is a means of protection by Allaah's Will, then this is a minor Shirk, because Allaah did not make it as a means of protection neither by legislation nor decree. The Prophet said: "Whoever wears an amulet, he has indeed committed an act of Shirk." [Ahmad] Furthermore, the Prophet said: "May Allaah not achieve (the aim) of the one who wears an amulet, and may Allaah not achieve the objective of whoever wears an item to protect him from envy and other evils." [Ahmad]
Allaah Knows best.