She is three weeks pregnant and her husband is threatening her with divorce if she does not abort the foetus
A number of scholars are of the view that it is permissible to abort the nutfah before forty days, as has been explained in the answer to question no. 115954.
Some of them limited it to cases where that serves an interest or wards off harm, as is mentioned in a statement of the Council of Senior Scholars, the text of which is as follows:
1 – It is not permissible to abort the pregnancy at various stages unless there is a shar’i justification for doing so, and within very narrow limits.
2 – If the pregnancy is in the first trimester, which is forty days, and there is a legitimate purpose to be served by aborting it or harm can be warded off thereby, then it is permissible to abort it. As for aborting it during this period just because one fears hardship in raising children or one fears being unable to afford the expenses of feeding them and educating them, or because of their future, or because the couple are happy with the number of children they have, that is not permissible. End quote from al-Fataawa al-Jaami’ah (3/1055).
Based on that, if you are afraid that your husband will divorce you if the pregnancy continues, and he is serious about that, then there is no sin on you if you abort the foetus within the first forty days of the pregnancy.
Shaykh Muhammad ibn Ibraaheem (may Allaah have mercy on him) said: From what we have seen above, it is seems that it is permissible to abort the nutfah. The evidence and reasons for that are clear.
As for the period in which it is permissible to abort the nutfah, it is forty days. End quote from Fataawa al-Shaykh Muhammad ibn Ibraaheem (11/125).
And Allaah knows best.