Biochemical analysis
Blood glucose and insulin were analysed with a Cobas Modular system
(Roche Diagnostics, Risch, Switzerland) at the Clinical Chemistry
Laboratory, Sahlgrenska University Hospital (accredited in accordance
with the International Standard ISO 15189:2007). HOMA-IR was calculated
as (fasting glucose × fasting insulin)/22.5 and HOMA-B as (20 × fasting
insulin)/(fasting glucose − 3.5)25. GDF15 was analysed
with an ELISA (Human GDF-15 Quantikine Elisa Kit, R&D Systems,
Minneapolis, MN, USA); serum samples during and after pregnancy were
diluted 1:64 and 1:4, respectively. The intra- and inter-assay CVs for
GDF15 measurements were 1.7% and 7%, respectively.