Does a pregnant woman menstruate?

In the book of the major ablution in Bidayat al-Mujtahid, Ibn Rushd treats the blood a pregnant woman sees, saying the jurists have differed "of old and of late" over whether it is menstruation or irregular bleeding. ¹

• A pregnant woman menstruates: held by Malik, by al-Shafi'i in the sounder of his two views, and others. ¹
• She does not menstruate: held by Abu Hanifa, Ahmad, al-Thawri and others, who say the blood she sees is the blood of disorder and illness. ¹
• The point of consensus: they agree that blood seen once labour pains begin is lochia, with the rulings of menstruation in barring prayer and the rest. ¹

Ibn Rushd notes that Malik and his followers have views he calls inconsistent on when a pregnant woman whose bleeding continues passes from the ruling of menstruation to that of irregular bleeding: that she is like any menstruating woman, waiting the maximum days of menstruation or adding three days to her usual days provided the total does not exceed fifteen; that she waits double the maximum days of menstruation; or that she multiplies the maximum days of menstruation by the number of months of her pregnancy. ¹

Ibn Rushd traces the disagreement to the difficulty of settling the matter by experience and the mixing of two cases: the blood a pregnant woman sees is sometimes menstrual blood, when her strength is ample and the foetus small - which is how a pregnancy upon a pregnancy becomes possible, as Hippocrates, Galen and the other physicians report - and sometimes the blood of illness, from weakness and illness of the foetus following her own, and most often it is the latter. ^{1 2} The editor of the Bayt al-Afkar edition gives this passage as an example of Ibn Rushd's use of medicine in law. ³

In the Book of Menstruation and Irregular Bleeding of al-Muhalla, Ibn Hazm lays down that any blood a pregnant woman sees before she delivers the last child in her womb is neither menstruation nor post-natal bleeding and prevents nothing; for the proof that it is not menstruation he refers back to the Book of Purity, and he says it is not post-natal bleeding because she has not yet delivered, and that there is no consensus that it is either. ⁴ From this he concludes that prayer, fasting and the permission of intercourse, whose obligation or permission is established, do not lapse for her without a firm text. ⁴ The editors note that this is the view of Abu Hanifa and his companions, of Ahmad and Ishaq ibn Rahwayh, and al-Shafi'i's earlier view; that Malik distinguished between bleeding early and late in pregnancy; and that al-Shafi'i's later view, the one relied on in his school, is that it is menstruation. ⁴

Each school's evidence from its own books and modern medical opinion are not given here; the page is limited to what Ibn Rushd reports.