Correlations between fasting plasma glucose level in the first trimester and gestational diabetes mellitus

Objective To investigate the relationships between fasting plasma glucose (FPG) level in early pregnancy and gestational diabetes mellitus (GDM).Methods Data of 11 477 pregnant women who accepted prenatal care in Beijing Obstetrics and Gynecology Hospital from October 2011 to September 2012 were collected.FPG was tested during 8 to 12 weeks of pregnancy in all women and those with FPG＜7.00 mmol/L were recruited.Women accepted 75 g oral glucose tolerance test (OGTT) during 24 to 28 weeks of pregnancy.The GDM diagnostic criteria was with reference to the criteria of International Association of Diabetes and Pregnancy Study Group.Mann-Whitney U test was used to analyze the difference of early pregnancy FPG between normal pregnant women and GDM women.Receiver operating characteristic (ROC) curve was used to analyze the validity and applicability of using early pregnancy FPG in GDM diagnosis.Chi-square test was used to analyze the relationship between the FPG levels and GDM diagnosis.Results There were 1 535 (13.4％) women diagnosed as GDM in 24 to 28 weeks of pregnancy (the rest 9 942 normal cases were taken as the controls).The median FPG level of the GDM group was 4.89 mmol/L (4.62-5.15 mmol/L),which was higher than that of the controls [4.75 mmol/L(4.53-4.98 mmol/L)] (Z=-13.994,P=0.000).The maximum area under curve (AUC),which was used to predict GDM with early pregnancy FPG,was 0.599 (95％ CI:0.582-0.617).Taking FPG 4.88 mmol/L as the cutoff value,the sensitivity was 0.523 and the specificity was 0.645.While taking FPG 5.10 and 5.60 mmol/L as the cutoff value,the sensitivity was 0.334 and 0.068,and the specificity was 0.811 and 0.983,respectively.When the FPG level ≤ 4.09,-4.60,-5.10,-5.60,-6.10 and ≥ 6.10 mmol/L,the GDM diagnostic rate gradually increased [8.5％(23/212),9.9％(335/3 379),12.3％(719/5 858),20.7％(359/1 734),40.2％ (78/194) and 52.5％ (21/40)] (x2=300.523,P=0.000).GDM diagnostic rate in FPG ≤ 4.09,-4.60,-5.10 and-5.60 mmol/L group were lower than that in FPG ≥ 5.60 but ＜6.10 mmol/L group and ≥ 6.10 mmol/L group (x2 were 67.242,164.680,128.125,37.860,55.843,76.856,58.589 and 23.484,all P=0.000) ; GDM diagnostic rate in FPG ≤ 4.09,-4.60,-5.10 mmol/L group were lower than that in FPG ≥ 5.10 but ＜5.60 mmol/L group (x2 were 22.877,113.717 and 78.040,all P=0.000); GDM diagnostic rate in FPG ≥ 4.09 but ＜4.60 mmol/L group was lower than that in FPG ≥ 4.60 but ＜5.10 mmol/L group (x2=11.803,P=0.001).When using abnormal fasting and postprandial OGTT level as GDM diagnostic criteria,the ratio of GDM in early pregnancy FPG level ≥ 5.60 but ＜6.10 mmol/L group and FPG ≥ 6.10 mmol/L group were higher than that of the FPG level ＜5.60 mmol/L group [50.0％ (39/78) and 71.4％ (15/21) vs24.1％ (346/1 436),x2 were 12.456 and 21.443,all P＜0.003].Conclusions Early pregnancy FPG level is not proper to be used as an early diagnostic tool of GDM.However,when early pregnancy FPG level is equal to or greater than 5.60 mmol/L,the incidence of GDM in late pregnancy will increase significantly. Key words: Blood glucose;  Pregnancy trimester, first;  Diabetes, gestational