Background B.OSS

In obstetric medicine we know several diseases and complications that can result in so-called near-miss events: ‘Severe life-threatening obstetric complications necessitating urgent medical intervention in order to prevent likely death of the mother‘.

Unfortunately rare obstetric diseases are not specifically listed as one of the important categories of conditions in the rare diseases consultation. Realizing that at least 2% of all females are pregnant at any given time, hence many millions of women will face the potential risk of obstetric complications, this should be considered as a meaningful misjudegment. Many of these obstetric complications cannot be anticipated by risk factors or tests. Obstetricians will be challenged by these complications at the most a few times along their clinical career, therefore individual expertise is scarce. Rare obstetric diseases are under-researched: there is no rigorous evidence on incidence, risk factors and pathophysiology and we lack evidence-based guidelines on prevention and management. 

The United Kingdom was a pioneer when developing the UK Obstetric Surveillance System (UKOSS) in 2006, a nationwide survey to identify and study  ‘near-miss’ events and  rare diseases of pregnancy. Collaboration of all maternities nationwide to collect data enables identification of a relatively small number of women. This allows to conduct descriptive epidemiologic studies, case-control and parallel cohort studies. Gathering experience and knowledge on incidence, risk factors, pathophysiology and management  results in better understanding, better patient information and care by practical improvements in prevention and treatment of these uncommon conditions. Since initiation in 2006 UKOSS has completed and published a large numer of studies (

Similar surveillance systems have been set up in other countries and the International Network of Obstetric Surveillance Systems (INOSS) has been constituted in July 2010. Current member countries of INOSS include Australia, Austria, Belgium, Denmark, Finland, France, Germany, Iceland, Italy, the Netherlands, New Zealand, Norway, Portugal, Slovakia, Spain, Sweden and the United Kingdom. The mission of INOSS is to co-operate, share information and enable cross-national comparisons and analyses  (

The Belgian Obstetric Surveillance System, B.OSS, supported by the College of Mother and Newborn, has been constituted in 2011 and started registering in the whole of Belgium as from January 2012. Meanwhile, the registration and evaluation of some diseases or rare complications in pregnancy has become a widely accepted practice in Belgium. Belgian gynaecologists are happy to receive advice based on own data, because practice in Belgium and certainly the organization of medical care do differ from that used in neighbouring countries. Whereas Peristat ( develops valid and reliable indicators that can be used for monitoring and evaluating perinatal health in the EU, the purpose of B.OSS in Belgium and of INOSS internationally is trying to analyse and explain the figures that are obtained and to establish the best possible treatment to avoid maternal near misses and deaths.


The purpose of B.OSS is to achieve a registry and a surveillance of rare maternal complications of pregnancy in Belgium: to bring together expertise on the knowledge and the management of these conditions,  so that in the future pregnant women with a rare complication of pregnancy could benefit through better information on the condition and the outcome of the condition.

Aim is to  conduct descriptive epidemiological studies  on rare obstetric disorders based on data  collected by B.OSS: to define prevalence  in Belgium and identify risk-factors, to describe and evaluate management and compare with international studies and guideline. Secondary objectives are to formulate recommendations for prevention: primary prevention (based on risk-factors) and secondary prevention (based on management and substandard care) and to formulate national guidelines.  

Aim is a high quality performance of the Belgian Obstetric Surveillance System (B.OSS) to be a respectable partner of INOSS, capable to co-operate and compare with other international obstetric surveillance systems.