The name of a female nurse and embryologist who played a crucial role in developing the world’s first test-tube baby was excluded from a plaque honouring the pioneers of IVF despite objections from her colleagues, newly released letters reveal.

Jean Purdy was one of three scientists whose groundbreaking work led to the birth of the first IVF baby, Louise Brown, in 1978. Yet her central role was largely forgotten in the rush to praise her colleagues, Prof Sir Robert Edwards and the surgeon Patrick Steptoe.

The letters show that Purdy’s name was left off a plaque honouring her two colleagues, despite protests from Edwards.

Letters revealed in Edwards’ archive show that he wrote to Oldham Area Health Authority in 1980 asking if it would be possible to have plaques at the hospitals involved “to do justice to the participants involved”, and he proposed including Purdy’s name.

In a reply from an administrator, he was told that the authorised wording would read: “Human in vitro fertilisation followed by the world’s first successful pregnancy, was performed in this hospital by Mr Patrick Steptoe, Dr Robert Edwards and their supporting staff in November 1977.”

Administrator David Killion wrote: “I hope you will find it sufficiently acceptable to enable us at least to put up something to commemorate your work, even if this does not describe it as fully or as clearly as you would wish.”

Edwards protested in a letter of 1981, writing: “I feel strongly about the inclusion of the names of the people who helped with the conception of Louise Brown. I feel this especially about Jean Purdy, who travelled to Oldham with me for 10 years, and contributed as much as I did to the project. Indeed, I regard her as an equal contributor to Patrick Steptoe and myself.”

However, the plaque at Kershaw’s Cottage hospital near Oldham was put up without Purdy’s name.

Facebook Twitter Pinterest Louise Brown, the world’s first baby to be born following successful in vitro fertilisation, at an event to celebrate 40 years of IVF. Photograph: Daniel Leal-Olivas/AFP/Getty Images

The letters have been released from Edwards’ private papers, which are held at Cambridge University’s Churchill Archives Centre and have been opened to the public following work to catalogue the collection funded by the Wellcome Trust.

Madelin Evans, an archivist, said the letters do not reveal an “explicit reason” why Purdy’s name was omitted but that “it probably had quite a bit to do with the fact she was a nurse, an embryologist and a woman I suppose”.

Asked if it was a case of sexism, she said: “I think it was probably one of the factors, and the fact probably that nurses weren’t seen as important maybe as doctors and scientists.”

Purdy, who died from cancer in 1985 aged 39, was described by Edwards as “crucial” to their IVF work and was the first person to witness the successful cell division of the embryo that would become Louise Brown.

Having initially joined the team as a lab technician, Purdy became so indispensable that work stopped for several months when she had to care for her ailing mother.

Edwards was awarded a Nobel prize in 2010 for the development of IVF and was knighted in 2011. Neither award can be made posthumously, so acknowledgment came too late for Purdy and Steptoe (who died in 1988) – but the discovery was a team effort.