‘Abdullaah bin Ahmad bin Hanbal said: I heard my father say:
‘Zakaat ul Fitr is to be given on behalf of the unborn child – if it is known of.’*
‘Abdullaah bin Ahmad bin Hanbal said: I heard my father say: Mu’tamir bin Sulaimaan At-Taymee narrated to us from Humaid from Bakr and Qataadah that ‘Uthmaan would give the Sadaqatul Fitr on behalf of the small child and the elder and the unborn child.
*Note: There occurs a narration from Imaam Ahmad with this meaning mentioned by Aboo Dawood in Al-Masaa’il page 86, and Ibn Haani’ in Al-Masaa’il vol 1 page 111 number 550.
As for the madhab itself (the Hanbali madhab): then within it the Zakaat ul Fitr is not obligatory on behalf of the foetus, this is because there is no ruling upon it until it is born. However; it is recommended that it is given on its behalf if it is known to exist due to the practice of ‘Uthmaan (radhiyallaahu ‘anhu). See: Mukhtasir Al-Kharqee page 75 and Al-Hidaayah vol 1 page 75 and Al-Mughnee vol 3 page 99 and Al-Furoo’ vol 2 page 526 and Al-Qawaa’id of Ibn Rajab page 189 and Al-Insaaf vol 3 page 168 and Al-Mubdi’ vol 2 page 388.