Praise be to Allah.
We should note that there is no specific prayer for ihraam, because it was not narrated from the Prophet (peace and blessings of Allaah be upon him) that he prescribed any prayer for his ummah for ihraam, neither in his words nor his deeds, nor did he approve of any such prayer.
The woman whose period started before she entered ihraam can enter ihraam whilst she is menstruating, because the Prophet (peace and blessings of Allaah be upon him) commanded Asma’ bint ‘Umays, the wife of Abu Bakr (may Allaah be pleased with him and with her), when she was bleeding following childbirth in Dhu’l-Hulayfah, to wash herself with a clothand enter ihraam. The same applies to the one who is menstruating. She should remain in ihraam until she becomes pure (i.e., her period ends), then she should do tawaaf around the Ka’bah and saa’i.
From the words of Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him), Sitteen Mas’alah fi’l-Hayd.
See also question no. 2564.