Two-hour 75-g Oral Glucose Tolerance Test Early in Pregnancy Detects Most Cases of Gestational Diabetes

doi:10.2337/diacare.25.4.803

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Letters

Two-hour 75-g Oral Glucose Tolerance Test Early in Pregnancy Detects Most Cases of Gestational Diabetes

Umesh Dashora, MD, MRCP, Vandana Dashora, MS and Lee Kennedy, MD, FRCP

Royal Sunderland Hospital, Sunderland, U.K.

We congratulate Schmidt et al. (1) for their excellent workon gestational diabetes mellitus (GDM), published in DiabetesCare. We would like to make several comments. We believe thattesting for GDM early in pregnancy would help to detect casesand has the potential to improve pregnancy outcomes. Also, WorldHealth Organization criteria for the diagnosis of GDM receivedfurther endorsement at the Fourth International Workshop-Conferenceon Gestational Diabetes Mellitus in 1977 (2); therefore, 2-h75-g glucose may be a better diagnostic test than fasting glucosealone (3) or the currently recommended American Diabetes Associationcriteria for GDM.

We tested 564 patients attending the antenatal clinic of IbraRegional Referral Hospital of Oman for glucose intolerance byglucose tolerance test using 75 g anhydrous glucose. Oral glucosetolerance tests (OGTTs) were performed at booking. If the resultswere normal, the test was repeated two or three times at 2-monthintervals, the last being at the 7th month of pregnancy. Wefound that 21.3% of pregnant women had abnormal glucose tolerancein Oman. A small proportion (1.1%) had high fasting values (>6mmol/l in venous plasma), whereas many (20.2%) had high post-glucosevalues (>7.8 venous plasma). Over 88% of the patients withGDM were diagnosed before the 7th month of pregnancy. Hence,a large proportion of cases were detected by a test early inpregnancy rather than the usual recommended time of screeningfor GDM at 7 months of pregnancy. In our study, 10% of womenrequired a second test, and 2.5% were diagnosed only at thethird test. Of the children born to the GDM subjects, 10% hada complication or abnormality.

Birth weight of the children in the GDM group was 3.13 kg (SD0.54) compared with 2.90 kg (0.44) in the nondiabetic group(P < 0.01). Three women with abnormal glucose tolerance gavebirth to large babies, weighing >4 kg, compared with onelarge baby in the control group of 388 subjects (relative risk10.2, P = 0.0017). Three babies in the abnormal glucose tolerancegroup had congenital abnormalities compared with one in thecontrol group (P = 0.013). Early and multiple screening forGDM has the potential to increase detection of GDM and to favorablyinfluence pregnancy outcome. We recommend a more aggressivescreening program for GDM in Oman and in other places with highprevalences of diabetes early in pregnancy.

Footnotes

Address correspondence to Dr. Umesh Dashora, Royal SunderlandHospital, Kayll Road, Sunderland, U.K. SR4 7 TP. E-mail: dashora{at}hotmail.com.

References

Schmidt MI, Duncan BB, Reichelt AJ, Branchtein L, Matos MC, Costa e Forti A, Spichler ER, Pousada JMDC, Teixeira MM, Yamashita T: Gestational diabetes mellitus diagnosed with a 2-h 75-g oral glucose tolerance test and adverse pregnancy outcomes. Diabetes Care 24:1151–1155, 2001[Abstract/Free Full Text]
Metzger BE, Coustan DR, the Organizing Committee: Summary and recommendations of the Fourth International Workshop-Conference on Gestational Diabetes Mellitus. Diabetes Care 21(Suppl. 2):B161–B167, 1998
Perucchini D, Fischer U, Spinas GA, Huch R, Huch A, Lehmann R: Using fasting plasma glucose concentrations to screen for gestational diabetes mellitus: prospective population based study BMJ 319:812–815, 1999[Abstract/Free Full Text]