Sheikh `Abd al-`Azîz b. Bâz
It was related from the Mother of Believers, Um Salamah, that she asked the Prophet (peace be upon him) about a woman’s bath (ghusl).
The Prophet (peace be upon him) told her: “When a woman performs ghusl after having sexual intercourse, there is no need for her to open up her hair. It is sufficient for her to pour water over her head three times. However, when she performs ghusl after completing her menstrual period, she has to open up her hair." [Sahîh Muslim]
Source: Islam Today