She overexerted herself in her house and had a miscarriage; does she have to offer expiation?
Question

                A woman miscarried when she was in the fourth month of pregnancy due to over exertion. She did not know that these efforts may cause a miscarriage. What is the ruling on this? Is it considered unintentional killing, should she fast then two consecutive months? What should she do if her period comes during fasting? 

These efforts were to prepare an invitation for her husband’s friends. He asked her for this.
Praise be to Allah.
    Firstly: 

    If what you did was something usual and there was no fear for 
    the foetus, then you do not have to do anything, because the basic principle 
    is that it is permissible for you to do these things. 

    But if the action was something that is usually known to be 
    harmful to the foetus, such as carrying heavy things, for example, which a 
    pregnant woman is not supposed to carry, and that resulted in miscarriage of 
    the foetus – in the fourth month, as mentioned in the question – then the 
    miscarriage of the foetus is not regarded as killing a person, because the 
    soul had not yet been breathed into it, as the soul is breathed into it 
    after one hundred and twenty days of pregnancy. 

    Based on this, there is no diyah (blood money) or kafaarah 
    (expiation) required as the result of this miscarriage. 

    Rather this miscarriage incurs a burden of sin, and you have 
    to repent and regret what you did. 

    The scholars of the Standing Committee for Issuing Fatwas 
    were asked : I went for Hajj with my husband and some of my children, and I 
    was four months pregnant. On the night of ‘Arafah we carried our luggage and 
    because we had so many things and they were heavy, I felt pain in my 
    stomach. On the same night I lost the foetus, and I buried it without 
    washing it or offering the funeral prayer for it. I was at the end of the 
    fourth month, and I had had some bleeding during the month of Dhu’l-Qa’dah. 
    After the miscarriage I had bleeding of nifaas, which lasted until the end 
    of Hajj. My question is: Do I have to do anything because of having a 
    miscarriage during this period? Please note that I did not wash him or offer 
    the funeral prayer for him, and I did not tell anyone about that, and the 
    miscarriage was not something that I wanted. 

    They replied: If the matter is as you describe, that the 
    pregnancy was in its fourth month and had not yet completed four months, 
    then you do not have to offer any expiation for the miscarriage of this 
    foetus, because the soul had not yet been breathed into it during this 
    period. Based on that, the foetus does not need to be given a name, washed 
    or prayed for, but you were sinning because you caused this miscarriage, so 
    you have to repent and pray for forgiveness for what happened, and not do 
    such a thing again in the future. End quote. 

    Fataawa al-Lajnah al-Daa’imah 
    (21/339). 

    Secondly: 

    If a woman starts to fast for two consecutive months then her 
    period comes, she should stop fasting during her period, then complete the 
    two-month fast after her period ends.

    Ibn Qudaamah (may Allaah have mercy on him) said: The 
    scholars are unanimously agreed that if a woman who is fasting for two 
    consecutive months gets her menses before she completes the fast, she should 
    make it up when she becomes pure (i.e., her menses ends) and she should 
    continue from where she was before her menses came. End quote from 
    al-Mughni (8/21). 

    And Allaah knows best.