C. Webb describes the Fanny Alger/Joseph relationship as a sealing and states that Fanny Alger was pregnant.
Wilhelm Wyl, Mormon Portraits: Joseph Smith the Prophet, His Family and His Friends: A Study Based on Facts and Documents (Salt Lake City: Tribune Printing and Publishing Company, 1886), 57
Mr. W.: "Joseph's dissolute life began already in the first times of the church, in Kirtland. He was sealed there secretly to Fanny Alger. Emma was furious, and drove the girl, who was unable to conceal the consequences of her celestial relation with the prophet, out of her house."
Mr. W. is Chauncey Griswold Webb as identified on page 6 of Mormon Portraits: Joseph Smith the Prophet, His Family and His Friends: A Study Based on Facts and Documents.