The literal definition of the Arabic term hayd is “to flow.” Legally, hayd refers to the physical blood that exits from the female body as well as the state of impurity a woman enters during the days of menstruation. Both prohibit her from specific ritual worship, such as fasting, prayer, and recitation of Qur’an.
Practically, hayd is blood which originates from the uterus and exits from the vaginal opening. At a minimum, a threshold of 72 hours must be reached and a maximum of 240 hours is allowed to be hayd. This correlates to 3 days/nights and 10 days/nights. When the blood aligns within these parameters, it is classified as valid blood. (Sunan al-Daraqutni 406-7/1, Al-Tabrani 129/8)
Post-Natal Bleeding (Nifas)
The literal definition of nifas is to give birth. Legally, nifas is blood which originates from the uterus and exits from the vaginal opening during childbirth. Once more than half of the child has exited from the vaginal canal, the blood is considered nifas. While there is no minimum duration, nifas cannot exceed 960 hours, or 40 days/nights. (Sunan al-Daraqutni 410/1, Al-Mustadrak 283/1)
Irregular Bleeding (Istihada)
Istihada exits from the vaginal opening, but unlike hayd and nifas, it is considered an invalid blood. Practically, it is that blood which a woman sees for less than three days or for more than ten days, i.e. below the minimum or beyond the maximum of menstruation, or for more than 40 days after childbirth. When a woman experiences bleeding out of her norm, it is important that she review her bleeding record to determine whether it falls under the category of hayd or istihada. (Sahih al-Bukhari 55/1 & 68/1, Sahih Muslim 262/1)