Is it true that both Faatimah, may Allaah be pleased with her, daughter of our beloved Prophet, sallallaahu alayhi wa sallam, and Maryam, may Allaah exalt her mention, the mother of 'Eesaa, may Allaah exalt his mention, did not menstruate (i.e. did not have periods) and that is why they are both called Zahraa?

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, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Some of the interpreters of the Quran said regarding the Saying of Allaah The Almighty (which means): {And (remember) when the angels said: "O Maryam (Mary)! Verily, Allaah has chosen you, purified you (from polytheism and disbelief), and chosen you above the women of the 'Aalameen (mankind and the Jinns) (of her lifetime).}[Quran, 3:42] That she is purified from all forms of impurities like menstruation, confinement period and so on. As-Suddi said that Maryam, may Allaah exalt her mention, never menstruated. However, we do not know that she is called Az-Zahraa'.

As for Faatimah some scholars stated that she never had menstruations and when she gave birth she was purified one hour later so that she would not miss even one prayer. Nevertheless, we do not know any authentic evidence regarding this. In principle women have menstruations as the Prophet, sallallaahu ‘alayhi wa sallam, told 'Aa'ishah when he, sallallaahu ‘alayhi wa sallam, found her crying when she had menstruations on the Farewell Pilgrimage: “This is a matter that Allaah has decreed on the daughters of Aadam (i.e. women)." [Al-Bukhari and Muslim]

In any case, both Maryam, may Allaah exalt her mention, and Faatimah do not need us to mention things that are not authentic about them to prove their excellence. Their excellence is proved in the books of Sunnah (Prophetic tradition). It is enough to mention the saying of the Prophet, sallallaahu ‘alayhi wa sallam: “The best women of Paradise are Khadeedjah bint Khuwaylid, Faatimah bint Muhammad, Aasiyah bint Muzaahim, who was the wife of Pharaoh, and Maryam bint 'Imraan." [Ahmad]

Allaah Knows best.