Imam al-Shafi'i (may Allah have mercy on him) said: When the Messenger of Allah (peace and blessings be upon him) gave judgement of a fine (ghurrah) for the fetus of a free woman, and it is not reported from him that he asked whether it was male or female — and the fetus is the pregnancy, so as long as the pregnancy is a single one, it is the same whether it is male or female — then likewise is the ruling on the fetus of a slave woman.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16429