Serum fructosamine and amniotic fluid insulin levels in patients with gestational diabetes and healthy control subjects Hannes M. H. Hofmann, MD, Peter A. M. Weiss, MD, Peter Piirstner, MS, Josef Haas, MS, Guenther Gmoser, MD, Karl Tamussino, MD, and Barbara Schmon, PhD Graz, Austria Gestational diabetic pregnancies with fetal hyperinsulinism should be identified because these cases require insulin therapy. To determine the relationship between the serum fructosamine and amniotic fluid insulin concentrations, these substances were measured in 87 pregnant women with impaired glucose tolerance. Fructosamine was also measured in 678 healthy pregnant control subjects, in 113 of whom amniotic fluid insulin levels were available. Fetal hyperinsulinism was rare at serum fructosamine levels of 30 yr (%) Height (cm) Prepregnancy weight (kg) >100 kg (%) Weight gain (kg) Gravidity Parity Therapy

Control subjects

Class A

Class B

678 26.1 :!: 3.4 12.7 165 ± 5.5 60.2 ± 8.5 3.3 13 ± 5.2 1.9 ± 1.0 0.7 ± 0.8 None

69 31.5 ± 8.1* 55.2t 164.7 ± 7.3 70.8 ± 13.3t 14.9t 9.6 ± 4.7 2.7 ± 1.8t 1.4 ± 1.6 Diet

18 28.1 ± 5.9* 36.8t 163.3 ± 7.5 70.6 ± 17t 15.8t 10.8 ± 8.3 2.4 ± l.4t 1.0 ± 1.2 Insulin

*P < 0.005, difference versus control subjects. tp < 0.001.

Table II. metabolic parameters, mean (SD) of 678 control subjects and 69 women with class A and 18 with class AB gestational diabetes Control subjects

Class A diabetes

Class AB diabetes

Number Fructosamine (mmoIlL) Oral GTT (fasting) (mg/dl) Oral GTT (I hr value) Oral GTT (2 hr value)

678 2246 (0.221) 70 (7.2)

69 2.286 (0.251) 83 (12.8)

18 3.029 (0.263) 88 (18.0)

NS *

* *

* NS

Il3 (21.1) 91 (19.5)

175 (17.0) 124 (27.8)

185 (28.7) 139 (34.0)

* *

*

*

NS NS

HbA,,, % AFI (fLU/ml) AFG (mg/ml)

4.27 (0.64) 3.84 (1.8) 27.62 (11.5)

4.49 (0.62) 4.43 (2.0) 35.73 (14.3)

4.65 (0.99) 23.56 (24.7) 48.17 (24.1)

NS

*

*

NS

*

*

*

A vs AB

*

*

AFI, Amniotic fluid insulin; AFG, amniotic fluid glucose.

*P < 0.01. Insulin was administered according to a basal bolus schedule." This study evaluated ony fructosamine values before treatment was begun. Table I summarizes the demographic data of the three groups. Statistical analysis was done with an analysis of variance followed by multiple t tests with a BonferroniHolm correction of the significance level. Results The maternal age in classes A and AB was higher than that in the control group (p < 0.005). Initial body weight and the number of spontaneous abortions also differed from the control group (p < 0.001). There were no differences in height, weight gain during pregnancy, or parity (Table I). Table II summarizes the metabolic parameters. The 95th percentile for serum fructosamine was 2.59 mmol/L, which was thus considered the upper limit of normal. Patients with class AB gestational diabetes differed from the control group in fructosamine, HbA,o and

amniotic fluid insulin levels as well as in oral GTT results (p < 0.01). Class AB differed from class A in fructosamine and amniotic fluid insulin, but not in HbAi< or oral GTT results. Class A differed from the control group in oral GTT results and HbA" but not in fructosamine or amniotic fluid insulin. The fructosamine values in the three groups are shown in Fig. 1. Fructosamine levels in women with class A gestational diabetes were very similar to those in the normal group. In contrast, class AB barely overlapped the other two groups. Comment The consequences of gestational diabetes, such as fetal macrosomia, obesity, and metabolic abnormalities, result from fetal hyperinsulinism. This in turn results from hyperstimulation of the fetal islet organ by high glucose levels. Its exposure to glucose depends on the maternal blood glucose level, placental glucose transfer, and the individual responsiveness of the fetal islet or-

1176

Hofmann et al.

May 1990 Am J Obstet Gynecol

_

Controls e

3.5

o

Class A

o

ClassAB