He is noted for coining the term 'Psi' to denote parapsychological phenomena;[1][2][3][4][5] for his research into human fertility and the diagnosis of pregnancy;[6][7] and for being the biological father of more than 600 people by anonymously donating sperm used by his wife the obstetrician Mary Barton to perform artificial insemination on women at her private practice in London.

Wiesner also researched the possibility of preventing and terminating pregnancy by physiological means without mechanical intervention based on oral ingestion of manufactured substances containing hormones.

[19][20][21] Two years later in 1927 the German gynecologists Bernhard Zondek and Selmar Ascheim discovered that the urine of a pregnant woman contained a substance later identified as the gonadotropic hormone human chorionic gonadotropin that caused an estrous reaction when injected into rats.

A number of notable scientists conducted research at the IAG, including physiologist John Scott Haldane, zoologist Lancelot Hogben and evolutionary biologist Julian Huxley.

Later, the scientists helped form the company Ayerst, McKenna and Harrison, Ltd (later, Wyeth) who marketed Premarin, a controversial hormone replacement therapy (HRT) drug based on pregnant mare's urine.

[39][40] While at the Institute of Animal Genetics, Wiesner resumed his earlier research into the prevention of pregnancy which contributed to the formulation of a reliable oral contraceptive for women.

[41][42][43] In addition, Wiesner collaborated with Kenneth Walker, a urological surgeon, at the Royal Northern Hospital where they had success in artificially inseminating women with sperm from anonymous donors in cases where the patient's husband was infertile or impotent.

[41] While working as an obstetrician at the Royal Free Hospital in London during the early 1940s, Mary Barton had also had similar success and founded the first private clinic offering artificial insemination in the United Kingdom.

[51] Wiesner's biological offspring, conceived by artificial insemination performed by Mary Barton and confirmed by DNA testing, include author and psychotherapist Paul Newham, barrister David Gollancz, writer Michael Bywater, comedian Simon Evans[52] and film maker Barry Stevens, whose documentary films were instrumental in facilitating and publicizing the process by which Wiesner's offspring can confirm their paternity.