Glycaemic control during pregnancy
We collected HbA1c concentrations during the first (n = 283), sec- ond (n = 276), and third trimesters (n = 262) from the local hospitals. We adopted a standardisation procedure to adjust for variations between the local HbA1c assays.14 We divided glycaemic control into three categories: mean HbA1c ≤ 6.0% (within normal range; “excellent”), mean HbA1c 6.1-7.0% (2-4 standard deviations from mean; “good”), and mean HbA1c > 7.0% (“not optimal”). We also asked the women to send a self obtained cap- illary blood sample to a central laboratory (Queen Beatrix Hos- pital, Winterswijk, Netherlands) for determination of HbA1c (HPLC, normal reference value 4.0-6.0%) early in pregnancy at about 10 weeks. We included only samples received between 8 and 14 weeks’ gestation (n = 227).
Severe hypoglycaemia occurring during the first and third trimesters was recorded. We defined severe hypoglycaemia as all episodes for which external help was needed, including hypoglycaemic coma.