WHC, which provides advice to women about their health, has become the patient arm of the BMS, a society for health professionals. WHC will retain its name and brand identity within the new organisation, which will operate under the British Menopause Society name.
The three part-time staff members at WHC and three part-time employees at the BMS will retain their jobs under the new structure. The charities already shared offices in Marlow, Buckinghamshire.
Sara Moger, chief executive of the BMS, will head the new organisation. Dr John Stevenson, WHC chair, and Patrick Shervington, honorary chief executive of the WHC, have been appointed as trustees of the BMS.
Nick Panay, consultant gynaecologist at the Chelsea and Westminster Hospital and chair of the BMS, said: "We have been close sister charities for many years. This formal merger will enable us to interact with more doctors and nurses and with women of all ages needing advice on a wide range of health, wellbeing and lifestyle issues."
Shervington said the merger was due to the need for cost-effectiveness.