In Sri Lanka, the prevalence of anaemia in pregnancy was estimated to be approximately 29% in 2001 but is estimated to have significantly reduced to be < 20%, at least in certain areas, during the last decade. Among its many causes, nutritional iron deficiency anaemia (IDA) is the commonest, but establishing a definitive diagnosis is difficult. Strategies adopted globally, as well as in Sri Lanka, to prevent IDA in pregnancy, have changed significantly during the last three decades. A comprehensive literature review was carried out and inter alia three relevant World Health Organization Guidelines, in which the author was a member of the guideline development group and six other publications of the author, on the topic of iron deficiency (ID) and IDA in pregnancy are included in this review. Ten studies on the detection and prevention of ID and IDA in pregnancy, carried out from 1990 to 2017 at the Academic Obstetrics and Gynaecology Unit (AOGU) of the Teaching Hospital Mahamodera, Galle (THMG) are described. The results and conclusions of these studies were: poor compliance and unsatisfactory methods of ingestion of the antenatal oral iron supplement could have contributed to the high rates of ID and IDA at term during the period 1990 to 1992; haematological indices during pregnancy need to be interpreted with caution; although the agreement between haematological indices obtained from different laboratories in Galle in 2000 was unsatisfactory, better agreement was observed in 2015; the rates of ID and IDA in pregnant women presenting for antenatal care to the AOGU of the THMG have significantly decreased from approximately 69% and 44% respectively in 1990 to approximately 37% and 17% respectively in 2015. Therefore, weekly antenatal oral iron supplements should be adequate to improve birth outcomes in the non-anaemic women attending this clinic.