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:
- Intercourse during the day in Ramadan is one of the gravest things that break the fast.
- The expiation for that is freeing a slave or fasting for two consecutive month or feeding sixty poor persons.
- This woman must fast even if she knows that she will have her period, and fasting is not waived unless she is unable to do it.
Answering your question, the Fatwa Center at Islam Q and A, states:
Intercourse during the day in Ramadan is one of the gravest things that break the fast. The one who does that must pray for forgiveness and repent, make up that day, and offer expiation.
The expiation for that, in order of precedence is: freeing a slave; if that is not possible, then it is fasting for two consecutive months; if one is not able to do that, then he must feed sixty poor persons.
It is not permissible to move from one expiation to the next option, except if one is unable to do it.
If the woman had an excuse at the time of having intercourse, such as if she was forced, or she forgot, or she was unaware of the prohibition of intercourse during the day in Ramadan, then there is no sin on her and she does not have to offer expiation.
There was a difference of scholarly opinion regarding the soundness of her fast on the day on which she was forced to have intercourse. But if she chooses to make up that day to be on the safe side, and paying attention to those scholars who say that this is obligatory, then that is a good thing.
But if she willingly obeyed her husband in having intercourse, and she had no excuse, then she must make up that day and offer expiation. This is the view of the majority of scholars.
If a woman is unable to fast because of a considerable health problem, then expiation in her case is to feed sixty poor persons. She may either give this food herself, or delegate her husband to give it on her behalf.
Getting one’s menses after having started the fast does not cancel the sequence of expiatory fasts; rather the woman should stop fasting when her menses comes, then when it ends, she should carry on from where she left off fasting, until she completes the two months. That is because menses is something that Allah has decreed for the daughters of Adam, and she has no control over it. There is scholarly consensus on this point.
Based on that, the mere fact that the period comes every month, or the fear of hardship, does not count as an excuse for moving to the option of feeding the poor; rather she must fast even if she knows that she will have her period, and fasting is not waived unless one is unable to do it.
Almighty Allah knows best.
Source: IslamQA.Info