Jean Sinclair (Clair) lsbister was a pioneer in the development of hospital and outpatient services for mothers and babies, particularly in the area of childbirth practices and post-natal care. Her epidemiological studies at the Royal North Shore Hospital and Tresillian led to the establishment of numerous programs for mothers, babies and the care of children.

Clair Isbister's grandfather, Joseph Beet, came to Australia from Devon in 1882 as a schoolteacher, with Clair's mother, Hannah, then three years old. He taught at Copperfield, near Claremont in central Queensland, then in Townsville, where Hannah excelled at school and was one of the first girls admitted to Townsville Boys Grammar School. She had hoped to become a doctor but became a nurse.

Clair's father, Peter Sinclair Paton, was a Scottish master builder who worked on Flinders Street Station in Melbourne and Brisbane City Hall. He met Hannah when admitted to hospital with appendicitis.

Clair, the eldest of three children, was christened Jean Sinclair Paton, but she preferred the abbreviation of Sinclair. Her father built a house at Doonan, near Eumundi. Clair has her early education at the school, also built by him. He then bought a dairy farm, which Clair grew to love, together with the bush, gardening, reading and entertaining herself. The family later moved to a banana farm, then to Sydney for the children's education. Clair attended St George Girl's High, where she was dux, and won scholarships to Sydney University, where she joined the Student Christian Movement and the League of Nations Union and met James Isbister also a medical student. They graduated in 1938.

After graduation, Clair completed her internship at Royal Prince Alfred Hospital and the Royal Alexandra Hospital for Children (RAHC.) James enlisted in the RAAF and they married in 1940. He was posted to the Tamworth RAAF Base soon after their marriage and Clair went with him. She worked later in Armidale covering for the local GPs who were in the forces. Later the couple went to England and completed their Royal College of Physicians (London) Memberships, before returning to Sydney with their young family. As a mother of four, Clair continued to work at RAHC and began working for Tresillian under the founder, Margaret Harper. Her work at Tresillian for the next twenty years enabled her to conduct some of her research studies in a non-hospital environment and use the data for comparison. At the same time, Clair began weekly radio talks on ABC Radio, speaking on many general medical topics, but mostly focussing on childbirth, child care and breastfeeding. Broadcasting policy of the time still dictated that such speakers remain anonymous, yet she became well known, particularly amongst rural listeners, as 'the Lady Doctor'. Reflecting back on these shows she said, "they were so important for country women who weren't getting information from other sources."

In 1948, she was appointed Consultant Paediatrician at Royal North Shore Hospital, Sydney and subsequently at the Blue Mountains District Hospital. At Royal North Shore she was appointed to the care of newborns, although her role was later broadened to include older children. She stayed at the Royal North Shore Hospital in varied capacities until her retirement in 1980, during this time conducting many of her medical studies of children. Early in her time there, she began studies of infections in children and established that newborns were contracting infections from the hospital environments, rather than their mothers. Her role at Tresillian helped her compare the different patterns of infection babies were presenting with in a non-hospital environment.

Clair's studies of lactating mothers resulted in changes in the management and teaching of breastfeeding to novice mothers. She also implemented simple techniques for looking after premature babies, for example, before the days of reliable incubators, she set up cots with electric blankets designed for pedigree Greyhound dogs. She was also responsible for the implementation of pre-delivery rooms for women in labour and their partners at Royal North Shore. Although there was some education for expectant parents, Clair established Preparation for Parenthood programs that were given by specialist doctors, nurses and physiotherapists. Her program included education on the management of pregnancy, childbirth and baby care, including lactation. With Clair's guidance, Royal North Shore established daytime visiting rights for parents of sick children and provided play facilities in the children's wards.

Working for the hospitals and Tresillian, and having conducted a major study of children with severe asthma, Clair became highly knowledgeable about allergies and asthma in children. She served as a volunteer for the Asthma Foundation for 36 years, during which time she developed the Asthma Swimming Program in which children were taught not only to swim, but also taught therapeutic techniques for breathing. The children's breathing capacity was tested prior to commencement of the program and were medically monitored throughout, thus enabling them to participate without fear. As part of her work with the Foundation, Clair also edited The Asthma Welfarer for 30 years. Since 1956, Clair has published numerous articles and books on topics relating to child care and child-birth.

In 1969, she was awarded an OBE for her services to mothers and babies, and was awarded a CBE in 1976 for her services to medicine. She was survived by sons, Peter, James and John, twelve grandchildren, many great-grandchildren and her sister, Jo Quinn.