A premature birth is defined as the birth of an infant before completion of the 37th week of pregnancy. A normal pregnancy lasts forty weeks. For premature infants – often called “preemies” – it lasts less than 260 days and they usually weigh less than 2500 grams.

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According to the World Health Organization (WHO), 15 million children worldwide are born prematurely every year. In the industrialised countries, it is five to ten percent of all deliveries. Premature births are one of the most frequent causes of death and long-term illnesses in newborns [1]. In Europe, the number of babies born prematurely amounts to around 500'000 per year, whereby the numbers in the individual countries differ considerably. For example, in Switzerland, there were 6.7% of children who came into the world too early in the year 2019. 3.3% of the babies born prematurely were born as a twin. This makes it clear that an elevated risk of premature birth exists for multiple births [2].