Types of amulets and superstition that some Muslims fall into
Question

Unfortunately there are some customs that are widespread among some mothers which are wrong and serious at the same time, and which go against Islam. These include: 
1. Hazaazah for the child who has hiccups They collect any amount of money, whatever it is, from seven people whose name has to be Muhammad, and they take it to a blacksmith to make what they call hazaazah, which they then place on the child’s clothes to take away the hiccups.
2. After giving birth, when the woman is still in the state of nifaas or postpartum bleeding, no other woman should enter upon her who has her monthly period, because that will prevent her from having children.
3. After small girls have been circumcised, they should not enter upon one another either.  And there are many other things of this nature. I want to know the religious evidence for the prohibition on this, because I believe that the first issue comes under the heading of amulets which are association of others with Allaah (shirk).
Praise be to Allah.Firstly: 
With regard to these myths which many people adhere to in word and deed, there is no evidence for them either in Islam or in terms of reason. Rather Islam forbids them and prohibits them, and they are forms of shirk. 
With regard to the three myths mentioned in the question: the first one comes under the heading of amulets; the second and third come under the heading of tiyarah or a superstition. It has been clearly stated that amulets and superstition are shirk. 
Secondly: 
With regard to the first myth: 
It comes under the ruling on amulets which they believe can bring benefit and ward off harm, and they are things which are worn such as beads, strings, horse shoes, blue eyes, “hands of Fatima” and many other things which they believe can bring good and benefit or ward off evil and harm. 
It was narrated that ‘Abd-Allah ibn Mas’ood (may Allah be pleased with him) said: I heard the Messenger of Allah (blessings and peace of Allah be upon him) say: “Ruqyah, amulets and love charms are shirk.” 
Narrated by Abu Dawood (3883) and Ibn Majaah (3530): classed as saheeh by al-Albani in Saheeh Abi Dawood.  
The ruling on the use of amulets -- including what is mentioned in the question of wearing hazaazah -- is that the one who acquires them or wears them, if he believes that they are a cause of bringing benefits and warding off harm and that benefit and harm are in the hand of Allah, then he has fallen into minor shirk, because he has made something that is not a means into a means. 
If he believes that it can bring benefit or cause harm in and of itself, then he has fallen into major shirk. 
What anyone who has taken anything of that nature or anything like it must do is get rid of it and repent to Allah. 
It was narrated from Abu Basheer al-Ansaari (may Allah be pleased with him) that he was with the Messenger of Allah (blessings and peace of Allah be upon him) on one of his journeys, and the people were at their places of rest. The Messenger of Allah (blessings and peace of Allah be upon him) sent a messenger (saying): “No camel is to be left among any group of people with a garland of sinew or a garland, but it is to be cut off.”  
Narrated by al-Bukhaari (2843) and Muslim (2115). 
Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have mercy on him) said: 
His words: “a garland of sinew or a garland” – the narrator was not sure, but the former is more likely, because garlands were made from sinew, and they believed that that could ward off the evil eye from the camels. This is a false belief, because it is placing one’s hope in a thing that is not a means or a cause. We have seen above that placing one’s hope in things that are not shar’i or tangible means or causes is shirk, because by placing his hope in them he is believing in them as means when Allah has not made them means, whether by His law or by His decree. Hence the Prophet (blessings and peace of Allah be upon him) ordered that these garlands be cut. End quote. 
Majmoo’ Fataawa al-Shaykh al-‘Uthaymeen (9/169) 
Thirdly: 
With regard to the second and third myths: 
These come under the heading of superstition. 
It was narrated from ‘Abd-Allah ibn Mas’ood that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Tiyarah (superstitious belief in bird omens) is shirk.” Narrated by Abu Dawood (3910) and classed as saheeh by al-Albani in al-Silsilah al-Saheehah (429). 
Reality shows these myths mentioned in the question to be false. Menstruating women often enter upon women who are in nifaas, to congratulate them or to uphold ties of kinship and that never prevented the woman from giving birth again. 
And why shouldn't girls who have been circumcised enter upon one another? 
What harm can be caused by a menstruating woman or woman in nifaas or a girl who has been circumcised entering upon a girl who has just been circumcised? 
There is no harm in that; rather this is just an illusion and myth which is in circulation among the common folk, as well as ignorance of Tawheed and of Islamic teachings, and it is their lack of common sense. 
We ask Allah to set the affairs of the Muslims straight. 
And Allah knows best.