The Herald-Sun reports that Dr Billings with his wife Dr Evelyn Billings pioneered the Billings Ovulation Method in the 1950s, a system that helps women to identify their fertile and non-fertile states based on their menstrual cycle.
Dr Billings, a neurologist who served with the Australian Imperial Force as a doctor in New Guinea during World War II, studied in London following the war but returned to practice in Melbourne.
He later became the head of the neurology department of St Vincent's Hospital, the clinical dean of its clinical school at the University of Melbourne and, from the late 1960s until recent years, the hospital's consulting neurologist.
But the work for which he was most famous began in 1953, when he was approached by the Catholic Church's Catholic Marriage Guidance Bureau to devise a method for couples to regulate their fertility.
Dr Billings and his wife have since spent more than 50 years researching fertility, and establishing WOOMB (The World Organisation Ovulation Method Billings International) in Melbourne as the centre for research and teaching the method around the world.
WOOMB director Marian Corkill said the Billings Method was taught in more than 100 countries including China, where it was the only natural fertility method accepted by the Government.
"His work was incredibly important, it has had a global effect.
"Australia has given people around the world a much greater understanding of fertility and it has given couples the opportunity to use that knowledge in a natural way to achieve or avoid pregnancy."
Dr Billings travelled the world to establish teaching centres and train teachers to educate women and couples about the method.
He was made a member of the Order of Australia (AM) in 1991 and also won a Papal knighthood for his work.
He is survived by his wife Evelyn, eight of his nine children and a growing family of grandchildren and great-grandchildren.
Better NFP promotion needed: Filipino lay leader says
Meanwhile, in the Philippines, Juliet Rivera, a lay leader of the Committee on Family Life Apostolate for Kalookan diocese, which includes Malabon city, has said that the Church must be more pro-active in promoting natural family planning methods.
Speaking at a public family planning event, Ms Rivera regretted a "cafeteria approach" to family planning promoted by NGOs which suggested "that artificial contraception is better because it's easier and more practical."
Rivera told UCA News that "activities like (the family planning event) must be a wake-up call for all members of the Church, to be proactive."
She submitted a proposal paper in late 2006 to Bishop Deogracias Iniguez of Kalookan indicating the committee's plans for "family and life centres in every parish," she said.
The diocese has 26 parishes. According to Ms Rivera, the bishop welcomed the suggestion. She hopes that "through our commission's new priest-coordinator, we can creatively propagate NFP."
Natural contraception pioneer dies (Herald-Sun, 2/4/07)
Fertility pioneer dies (The Age, 3/4/07)
Cafeteria-Style Kiosks Show Parishioners Prefer Artificial Birth Control Methods (UCA News, 2/4/07)
LINKS (not necessarily endorsed by Church Resources)
World Organisation for Ovulation Method Billings
Billings ovulation method (Wikipedia)
Natural family planning as good as pill, study finds (CathNews, 23/2/07)
Public servant defends funding for Church pregnancy advice (CathNews, 18/2/05)
New President for Natural Family Planning Council (CathNews, 16/11/04)
3 Apr 2007