Prediction of infant birth weight by GDM screening tests. Importance of plasma triglyceride.
OBJECTIVE
We measured plasma glucose, GHb, GPro, IRI and TG at 24-28-wk gestation to determine the extent of elevations in GDM and relationships to glucose intolerance and infant macrosomia.


METHODS
Plasma samples were obtained 1 h after ingestion of 50 g glucose after an overnight fast in 521 randomly selected negative screenees, 264 positive screenees with GTT-, and 96 positive screenees with GTT+ (GDM).


RESULTS
Screening test values in GDM subjects exceeded the GTT- group, whose values exceeded those of negative screenees: glucose, 9.6*, 8.7*, 6.3 mM; GHb, 5.2*, 4.9*, 4.7%; GPro, 3.1*, 3.0*, 2.8%; IRI, 791*, 662*, 410 pM; and TG, 2.3*, 1.9, 1.9 mM, (*P < 0.005 vs. negative screenees). TG was the only test elevated in the GDM but not in the GTT- groups. Screening test values correlated with GTT values in the following order (strongest to weakest): glucose* > TG* > GHb* > IRI > GPro (*statistical significance). Plasma TG was the only screening test significantly associated with birth weight corrected for gestational age (birth-weight ratio) (r = 0.09-0.16) (P < 0.05 to < 0.01) and was of the same order as 1- and 2-h GTT associations with birth weight (r = 0.13 and 0.14, respectively) (P < 0.05 to < 0.01). Plots of TG/birth-weight ratio increased linearly to the 80-90th TG percentile in negative screenees and GTT- subjects. GDM subjects followed this trend but with more variation. Above the 90th percentile for TGs, birth-weight ratio trended lower, significantly so when the groups were combined (P < 0.05). In multivariate analysis, TG was associated with birth-weight ratio even when maternal prepregnancy weight and pregnancy weight gain associations with TG and birth-weight ratio were controlled (P < 0.019).


CONCLUSIONS
Of the five screening tests evaluated, all were elevated in GDM, but TG is the best discriminator of GDM from the GTT- group, and it is the only test significantly related to birth-weight ratio--and to glucose intolerance besides glucose itself. The TG association with birth weight is not explained fully by maternal weight. The results suggest that plasma TG may be a physiological contributor to infant birth weight. Further evaluation of plasma TG in GDM screening is justified, but GHb, GPro, and IRI appear to hold less promise.
Knopp
R H
RH
Department of Medicine, School of Medicine, University of Washington, Seattle.
Magee
M S
MS
Walden
C E
CE
Bonet
B
B
Benedetti
T J
TJ
D000704:Analysis of Variance; D001724:Birth Weight; D001786:Blood Glucose / Q000378:metabolism; D016640:Diabetes, Gestational / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007231:Infant, Newborn; D007328:Insulin / Q000097:blood; D008875:Middle Aged; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007328:Insulin; D014280:Triglycerides