The CRADLE Vital Signs Alert

‘A simple, effective solution to reduce maternal mortality and morbidity worldwide.’


Every day around 810 women die from preventable causes related to pregnancy and childbirth.  Ninety-four percent of all maternal deaths occur in low and middle income countries.  The major complications that account for nearly 75% of maternal deaths are: haemorrhage (severe bleeding mostly after childbirth); sepsis (infection usually after childbirth); hypertension (high blood pressure during pregnancy known as pre-eclampsia which can lead to eclampsia or seizures and/ or stroke).1 Each of these conditions is associated with abnormalities in vital signs (blood pressure – BP and heart rate – HR)2, and are mostly preventable, through simple, affordable interventions administered in a timely way.  But, in low income, resource poor settings abnormal vital signs go undetected, due to a lack of functional accurate equipment and inadequate training of frontline workers.

In answer to these challenges a team at King’s College London developed the CRADLE (Community blood pressure monitoring in Rural Africa & Asia: Detection of underLying pre-Eclampsia and shock) Vital Signs Alert (VSA) to enable accurate vital signs measurement  in pregnant women in low income settings.  To date, over 10 000 CRADLE VSA devices have been used clinically in Africa, Asia and the Caribbean, and was the first accurate blood pressure device for pregnancy in the majority of clinics and hospitals, where it has resulted in a reduction in maternal mortality and morbidity.  For example, introduction of the CRADLE VSA to Primary Healthcare Facilities in Sierra Leone during CRADLE 3 trial was associated with a 60% reduction in maternal death, and a 40% reduction in eclampsia.3  Its simple technology could significantly contribute to United Nations Sustainable Development Goal 3: to reduce global maternal mortality to less than 70 per 100 000 live births by 2030.

The CRADLE VSA is one of the first blood pressure devices to be shown to be accurate in pregnancy.  The device has been validated for detecting high blood pressure4, and abnormally low blood pressure with a fast heart rate, crucial in the detection of shock secondary to infection or bleeding.5 It is also accurate in non-pregnant adults, increasing its widespread appeal in rural areas.6



  1. World Health Organisation. Maternal Mortality. [Accessed on 15th June 2021 at who.int: https://www.who.int/news-room/fact-sheets/detail/maternal-mortality].
  2. Alkema L, Chou D, Hogan D, Zhang S, Moller AB, Gemmill A, et al. Global, regional, and national levels and trends in maternal mortality between 1990 and 2015, with scenario-based projections to 2030: A systematic analysis by the un Maternal Mortality Estimation Inter-Agency Group. Lancet [Internet]. World Health Organization. Published by Elsevier Ltd/Inc/BV. All rights reserved.; 2016;387(10017):462–74. Available from: http://dx.doi.org/10.1016/S0140- 6736(15)00838-7
  3. Vousden N, Lawley E, Nathan HL, Seed PT, Gidiri MF, Goudar S et al. Effect of a novel vital sign device on maternal mortality and morbidity in low-resource settings: a pragmatic, stepped-wedge, cluster-randomised controlled trial Lancet Glob Health 2019; 7: e347–56
  4. Nathan HL, de Greeff A, Hezelgrave NL, Chappell LC, Shennan AH. An accurate semi- automated oscillometric blood pressure device for use in pregnancy (including pre-eclampsia) in a low-income and middle-income country population: the Microlife 3AS1-2. Blood Press Monit 20:52– 55, 2015 Wolters Kluwer Health, Inc.
  5. Nathan HL, de Greeff A, Hezelgrave NL, Chappell LC, Shennan AH. Accuracy validation of the Microlife 3AS1-2 blood pressure device in a pregnant population with low blood pressure. Blood Press Monit Wolters Kluwer Health, Inc.
  6. de Greeff A, Nathan H, Stafford N, Liu B, Shennan AH. Development of an accurate oscillometric blood pressure device for low resource settings. Blood Press. Monit. 2008;13(6):342–8.