All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
There is no harm in having more than one wet-nurse for a newborn child. This is permissible, in principle, unless proven prohibited by a revealed text. There is nothing wrong with this practice provided that it does not negatively affect the child or bring harm upon him.
The Prophet, sallallaahu ‘alayhi wa sallam, had more than one wet-nurse. Ibn Al-Qayyim wrote in the chapter on the wet nurses of the Prophet, sallallaahu ‘alayhi wa sallam, “Some of them were Thuwaybah, the slave girl of Abu Lahab, who nursed the Prophet, sallallaahu ‘alayhi wa sallam, for some days together with Abu Salamah ‘Abdullah ibn ‘Abd Al-Asad Al-Makhzoomi with the milk of her newborn Masrooh. She nursed with them Hamzah ibn ‘Abd Al-Muttalib, the paternal uncle of the Prophet . There are different scholarly opinions regarding whether she embraced Islam or not. Then, Haleemah As-Sa‘diyyah nursed the Prophet, sallallaahu ‘alayhi wa sallam, along with her newborn ‘Abdullaah. Hamzah ibn ‘Abd Al-Muttalib the Prophet’s paternal uncle, happened to be nursed by a wet-nurse from Banu Sa‘d ibn Bakr as well. His mother (through breastfeeding) nursed the Prophet, sallallaahu ‘alayhi wa sallam, some days when he, sallallaahu ‘alayhi wa sallam, was with Haleemah.” [Zaad Al-Ma‘aad]
Allaah Knows best.