Adverse pregnancy outcome among women with pre-gestational diabetes mellitus: a population-based multi-centric study in Beijing.

Objective: To investigate the prevalence of pre-gestational diabetes mellitus (pGDM) incidence and to evaluate whether the 2-h plasma glucose value of the oral glucose tolerance test (OGTT) should be used to diagnose pGDM during pregnancy.
Design: Observational cohort study of 15 194 women in 15 medical centers in Beijing from 20 June 2013 to 30 November 2013. The incidence of adverse pregnancy outcomes among women with pGDM was compared stratified according to diagnostic time and criteria.
Results: The prevalence of pGDM was 1.4% (208/15 194), of which only 32.2% (67/208) were diagnosed before pregnancy. The incidence of cesarean delivery (53.8% versus 67.2% and 66.3%), preeclampsia (1.9% versus 11.9% and 8.0%), insulin required (38.5% versus 65.7% and 52.8%) in those with 2-h plasma glucose ≥11.1 mmol/L during is lower than those with pGDM known prior pregnancy or diagnosed during pregnancy according to hemoglobin A1c (HbA1C) ≥ 6.5% or fasting plasma glucose (FPG) ≥ 7.0 mmol/L.
Conclusions: More than two-thirds of pGDM patients were diagnosed during pregnancy. FPG should be used as screening test to identify pGDM at first antenatal care. An abnormal 2-h glucose value only may not be suitable to diagnose pGDM during pregnancy in China.