How authentic is the Hadith mentioned in the question?

The aforementioned hadith (definition) was not found, but a similar hadith was narrated on the authority of Abu Hurairah, which states: "When a woman becomes pregnant, she has the reward of one who fasts, prays, is devout, humble, and strives in the way of Allah – Almighty and Exalted. When labor pains strike her, none of the creation knows what reward she has. When she gives birth, for every birth she performs, she frees a soul." This was narrated by Ibn Hibban in "Al-Majrooheen," and he mentioned that it contains Al-Hasan (definition) ibn Muhammad al-Balkhi, who narrates fabricated and inverted hadiths. Al-Albani judged this hadith to be mawdu' (fabricated), meaning it is a lie attributed to the Prophet (peace and blessings of Allah be upon him).