Cronk was born in Glasgow in 1932, the daughter of a Clydeside ship worker.
[1] She first studied nursing at Glasgow Royal Infirmary, and in 1957 started training to be a midwife at Queen Charlotte's in London.
Cronk joined the English National Board of the United Kingdom Central Council for Nursing, Midwifery and Health Visiting, and served on the RCM Council between September 1999 and August 2003.
Cronk also wrote many articles on midwifery, covering a variety of topics, including physiological breech birth, of which she was a proponent.
[5][6] Once retired, Cronk continued to educate by hosting study days alongside fellow independent midwife Jane Evans; the pair disseminated information on unusual but normal births, including breech birth.