Study design and participants
This prospective observational multicentre study was conducted from January 2016 to March 2020 at seven different maternity clinics in Sweden (three regional clinics: Helsingborg, Ystad and Kristianstad, with a total of 7500 annual deliveries) and four tertiary clinics, Skåne University Hospital (9000 annual deliveries), Sahlgrenska University Hospital (10000 annual deliveries), Söder Hospital (8000 annual deliveries) and one in Australia, Westmead Hospital, Sydney (6000 annual deliveries).
Inclusion criteria were indication for fetal scalp blood sampling due to suspicious or pathological CTG patterns in labour, singleton pregnancy ≥35+0 gestational weeks (according to ultrasound dating in the first or second trimester), vertex presentation, and no contraindication for FBS (infections with risk for vertical transmission or suspected fetal thrombocytopenia or haemophilia).