Abdullah bin Nujayy narrates from Sayyiduna Ali (may Allah be pleased with him) that he used to accept the testimony of the midwife; Abu Awanah added: alone.
This is not sound: Jabir al-Ju'fi is matruk (abandoned), and Abdullah bin Nujayy is questionable. Suwayd bin Abd al-Aziz, who is da'if (weak), also narrated it from Ghaylan bin Jami', from Ata bin Abi Marwan, from his father, from Ali (may Allah be pleased with him). Ishaq al-Hanzali said: If the testimony of the midwife were authentic from Ali (may Allah be pleased with him), we would hold it, but there is a defect in its chain.
Imam al-Shafi'i (may Allah have mercy on him) said: It is not established from Sayyiduna Ali (may Allah be pleased with him); otherwise we would act on it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20544