From the New York Times obituary:
John Billings, an Australian physician who more than half a century ago developed a natural contraception method endorsed by the Roman Catholic Church, died Sunday in Melbourne. He was 89 and a lifelong Melbourne resident…
A neurologist by training, Dr. Billings began investigating natural contraception, that is, techniques not relying on devices or drugs that block conception, in 1953, at the request of the Catholic Marriage Guidance Bureau in Melbourne. Working with his wife, Dr. Evelyn Billings, a pediatrician, he created what is now known as the Billings ovulation method, or the Billings method. The method relies on a woman's ability to sense changes in the amount and texture of her cervical mucus, which help predict ovulation and fertility.
And here's where the irony meter soars:
Besides his wife, the former Evelyn Thomas, whom he married in 1943, Dr. Billings is survived by eight of their nine children (emphasis added), and many grandchildren and great-grandchildren.
If natural family planning is followed perfectly pregnancies result between 1 to 9 percent of the time depending on the method. However compliance (that is, chiefly periodic sexual abstinence) is rarely perfect, so actual the actual pregnancy rate is closer to 25 percent.