What is the ruling on al-Ghīlah —may Allah reward you—?

If "al-ghilah" refers to a man having intercourse with his breastfeeding wife, or a woman breastfeeding while pregnant, there is no harm in that. The Prophet (peace be upon him) intended to prohibit it, but then mentioned that the Persians and Romans do it and it does not harm their children, which indicates its permissibility. Doctors believe that the milk of a breastfeeding pregnant woman may be a disease, but the hadith (definition) indicates that its harm is not to the extent that would necessitate a general prohibition.