Table 2

Maternal and fetal metabolic parameters comparing women with normal glucose tolerance, impaired glucose tolerance, and gestational diabetes mellitus

Normal glucose toleranceImpaired glucose toleranceGestational diabetes mellitusP value for difference trendAdjusted P value*
n1913126
Mother in pregnancy
First trimester, random blood
    Glucose (mg/dl)83.4 ± 14.185.2 ± 12.590.4 ± 15.90.130.050.48
    Glucose (mmol/l)4.6 ± 0.84.7 ± 0.75.0 ± 0.9
24–28 weeks, 50 g OGTT
    Glucose (mg/dl)105.6 ± 17.9152.8 ± 12.7170.4 ± 28.8§<0.0001<0.0001<0.0001
    Glucose (mmol/l)5.9 ± 1.08.5 ± 0.79.5 ± 1.6
    Insulin (mU/ml)39.4 ± 53.669.3 ± 69.093.0 ± 76.6§<0.0001<0.0001<0.0001
    Insulin (pmol/l)236.5 ± 321.5415.6 ± 414.0557.9 ± 459.5§
    Proinsulin (pmol/l)17.5 ± 10.921.3 ± 15.627.3 ± 21.3<0.0001<0.0010.003
    Proinsulin-to-insulin ratio0.07 ± 0.080.05 ± 0.040.05 ± 0.050.200.120.11
32–35 weeks, random blood
    Proinsulin (pmol/l)16.6 ± 13.420.3 ± 18.517.8 ± 23.40.300.280.47
Fetus (cord blood)
    Glucose (mg/dl)84.7 ± 17.478.7 ± 11.181.1 ± 16.70.120.130.12
    Glucose (mmol/l)4.6 ± 1.04.4 ± 0.64.5 ± 0.9
    Insulin (mU/ml)4.1 ± 4.84.3 ± 3.27.8 ± 8.2<0.0010.0010.02
    Insulin (pmol/l)24.8 ± 28.625.7 ± 19.147.0 ± 49.2
    Glucose (mg/dl)-to-insulin (μU/ml) ratio20.0 ± 24.218.2 ± 14.510.1 ± 10.0<0.001<0.0010.03
    Proinsulin (pmol/l)13.8 ± 9.414.9 ± 8.724.4 ± 15.8§<0.0001<0.0001<0.0001
    Proinsulin-to-insulin ratio0.56 ± 0.590.58 ± 0.440.52 ± 0.420.840.760.40
  • Data are means ± SD unless otherwise indicated. Geometric means are presented for biomarkers (insulin, proinsulin, glucose-to-insulin ratio, and proinsulin-to-insulin ratio) with highly skewed crude data distributions. Pseudo-SDs (in regular scale) are presented for geometric means by calculating the average SDs within the 95% CIs (1 SD change is not a constant in back-transformation from the log to regular scale, larger in the upper tail). 50 g OGTT = 50 g, 1-h OGTT.

  • *Adjusted P values for the differences across the three study groups. For maternal measurements, the comparisons were adjusted for ethnicity, age, parity, smoking, alcohol use, and prepregnancy BMI (SD score); for cord blood measurements, the comparisons were further adjusted for family history of diabetes, weight gain in pregnancy (SD score), gestational hypertension, bacterial vaginosis and other minor infections (no major infections reported), mode of delivery, maternal glucose (5% dextrose, in all such cases) infusion during delivery, infant sex, gestational age, birth weight (SD score), and ponderal index (SD score).

  • P < 0.05;

  • P < 0.01;

  • §P < 0.001, for comparisons to the reference group (normal glucose tolerance) after the adjustments; similar differences were observed in boys and girls (data not shown).

  • ‖The same unit (picomoles per liter) was used for both insulin and proinsulin in calculating the proinsulin-to-insulin ratio.