Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Performing a marriage contract with a woman while she is menstruating is permissible and valid.
The late prominent Saudi Muslim scholar, Sheikh Ibn Uthaymeen, stated:
Is marriage during menses valid in Islam?
Performing a marriage contract with a woman while she is menstruating is permissible and valid. There is no harm in it.
The basic ruling concerning contracts is that of permissibility and legality unless there is evidence to show that it is not allowed.
There is no evidence to show that one may not finalize a marriage contract while the woman is menstruating. Therefore, the aforementioned contract is sound. There is no harm in it.
One must also understand and know the difference between the marriage contract and divorce. Divorce is not permissible while the woman is menstruating. In fact, it is forbidden.
Prophet Muhammad (peace be upon him) became angry when it reached him that `Abdullah ibn `Umar ibn al-Khattab had divorced his wife while she was menstruating.
Prophet Muhammad ordered that he goes back to her and not touch her until she became pure, had her menses again and then became pure again. Then he could afterwards remain with her or divorce her. (Al-Bukhari and Muslim)
Furthermore, Allah has stated,
{O Prophet! When you divorce women, divorce them at their prescribed periods (iddah) and count (accurately) their periods. And fear Allah your Lord. And turn them not out of their [husband’s] homes, nor shall they [themselves] leave, except in cases where they are guilty of open illegal sexual intercourse. Those are the set limits of Allah. Whosoever transgresses the set limits of Allah, then indeed he has wronged himself.} (Al-Talaq 65:1)
So it is not allowed for a man to divorce his wife while she is menstruating. He also cannot divorce her during a time of purity in which they had had sexual intercourse, unless it is clear that she is pregnant. If it is clear that she is pregnant, he may divorce her whenever he wishes and that divorce will take effect.
Is divorce during pregnancy valid in Islam?
It is very strange that among the masses there is a common misconception that a divorce stated while the woman is pregnant does not take effect. This is not correct. The divorce of a pregnant woman does take effect. In fact, the rules are more liberal concerning it.
For example, it is permissible for a man to divorce his pregnant wife even if he had just recently had sexual intercourse with her. This is not so for woman who is not known to be pregnant. If he has intercourse with her, he must wait until her next menses and their finishing or it becomes clear that she is pregnant before he pronounces divorce.
Allah states,
{For those who are pregnant, their waiting period is until they deliver.} (Al-Talaq 65:4)
This is a clear indication that such a divorce does take effect. Furthermore, in some of the hadith of Ibn Umar, it is narrated that the Prophet (peace be upon him) said,
“Order him to return to his wife and then divorce her when she is pure [of her menses] or she is pregnant.” (Muslim)
If it is clear that the marriage contract done while the woman is menstruating is a sound marriage contract, I still feel that the man should not enter upon the woman [be with her alone] until her menses come to an end.
This is because if he does join her before she becomes pure, it is feared that he may engage in an act which is forbidden while she is menstruating, especially if he is not able to control himself. Especially if he is a young man, he should wait until she becomes pure, at a time when he is able to enjoy her company by sexual intercourse.
Almighty Allah knows best.
Source: Islamic Fatawa Regarding Women, Compiled by Muhammad Ibn Abdul-Aziz Al-Musnad and translated by Jamal Al-Din Zarabozo, Darussalam, 1996.