Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
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.
Thanks for your interesting question, and we earnestly implore Allah to increase our knowledge about Islam and guide us all to the best.
There is nothing wrong in making use of the human milk banks as long as there is an apparent necessity to do so. Benefiting from the milk kept in human milk banks does not entail prohibiting marriage because of nursing because the milk in those banks is a mixture of milk donated by a number of unidentified wet nurses.
Responding to the question, the European Council for Fatwa and Research, states:
The members of the Council discussed the topic of providing Muslim children—particularly the premature and underweight babies—with milk from the human milk banks widely available in Western countries, which such babies are badly in need of to save their lives.
After looking into the decision taken by the International Islamic Fiqh Academy concerning the establishment of milk banks in the Muslim world and the prohibition of nursing from them, the Council reviewed the technical and Shar`i studies submitted by some of its members on milk banks.
Due to the change in the criteria on which the decision of the International Islamic Fiqh Academy was based, particularly what concerns the Muslims residing in Western countries, where milk banks have existed for a long time and where they increase in number and spread from one country to another; and due to the increase in the number of Muslims residing in the West and the absence of identified wet nurses, as is the case in the Muslim world, the Council decided the following:
1- There is no objection in terms of the Shari`ah to benefiting from the milk of the milk banks when necessary.
2- Benefiting from this milk does not entail prohibiting marriage because of nursing. This is partly because the number of nursing times is unknown, and partly because the milk is mixed and the wet nurses cannot be identified because of the legal prohibition on disclosing the names of the milk donors.
This is in addition to the large number of donors. The decision is based on consulting the jurists’ decision that marriage is not prohibited in the case when a baby is nursed by an unknown woman in a village, due to the impossibility of identifying her, and on the fact that the milk offered by these banks is a mixture of milk donated by a number of unidentified wet nurses and the major proportion of it is unknown.
Almighty Allah knows best.