On 10 March 1720 he was elected a Fellow of the Royal Society, and on 30 September in the same year was admitted a licentiate of the London College of Physicians.
[1] In 1726 Manningham published Exact Diary of what was observed during a close attendance upon Mary Toft the pretended Rabbit Breeder.
Manningham, working with James Douglas, showed that these were pieces of adult and not of young rabbits, and that Toft was not parturient.
[1][4] Manningham published in 1740 Artis Obstetricariæ Compendium; the parts of the subject of obstetrics are arranged in tabular forms, each tabulation being followed by a series of aphorisms.
He lived in his father's house in Jermyn Street, London, till 1780, when he went to Bath, Somerset, and died there 3 February 1794.