Risk Factors for Gestational. Diabetes in Black Population. David S.H. Bell, MD. Bruce 0. Barger, PhD. Rodney C.P. Go, PhD. Robert L. Goldenberg, MD.
Risk Factors for Gestational Diabetes in Black Population
In a long-term longitudinal study of gestational diabetes mellitus in Black women, risk factors that were identified were age, obesity, a family history of diabetes, and the presence of hypertension. Poor predictors were a history of a previous large-for-date infant, parity, and age at first pregnancy. The prevalence of smooth muscle and nuclear autoantibodies was higher in gestational diabetic subjects. Gestational diabetic subjects who required insulin for glycemic control were more obese, had a lower frequency of the Bf-F phenotype and a higher frequency of the Bf-F1 phenotype, and had a lower frequency of the type 2 allele at the polymorphic locus adjacent to the insulin gene. Restriction-fragmentlength polymorphisms flanking the insulin and apolipoprotein A-l and C-MI genes, although not associated with gestational diabetes mellitus, may be associated with hyperlipidemia and subsequent atherosclerosis. Diabetes Care 13 (Suppl. 4): 1196-201, 1990
WHAT IS GESTATIONAL DIABETES? Gestational diabetes has been defined as glucose intolerance developing during pregnancy (1). Risk factors identified in other populations have been obesity, a family history of diabetes, a previous large-for-date infant, high maternal age, multiparity >5, previous perinatal death, or previous fetal malformation (2-7). After screening, gestational diabetes, as in this study, is usually diagnosed by a glucose tolerance test with the criteria of O'Sullivan and Mahan (8), which state that,
From the University of Alabama at Birmingham, Birmingham, Alabama. Address correspondence and reprint requests to David S.H. Bell, MD, University of Alabama at Birmingham, Birmingham, AL 35294.
1196
David S.H. Bell, MD Bruce 0 . Barger, PhD Rodney C.P. Go, PhD Robert L. Goldenberg, MD Laura L. Perkins, PhD Chotip J. Vanichanan, MD Jeffrey Roseman, MD, PhD, MPH Ronald T. Acton, PhD
after 100 g of glucose, two or more of the following values for plasma glucose must be met or exceeded: fasting, 5.8 mM; 1 h, 10.6 mM; 2 h, 7.5 mM; and 3 h, 8.0 mM.
WHAT ARE CONSEQUENCES OF GESTATIONAL DIABETES? The consequences of gestational diabetes include congenital malformations; complications of pregnancy including preeclampsia and kidney problems; intrauterine death, especially when ketoacidosis occurs; macrosomia; and neonatal hypoglycemia. In women who have persistent hyperglycemia, hyperinsulinemia occurs in the fetus so that insulin acts as a growth factor and causes macrosomia (9). Also, as a result of fetal hyperinsulinemia, neonatal hypoglycemia often occurs. Due to the immaturity of the fetus, respiratory distress syndrome is common in the newborn, and it has been reported that there are lowered IQ and neuropsychiatric deficits in the offspring of mothers who have persistent hyperglycemia and ketosis during pregnancy (10-14).
WHAT IS PROGNOSIS FOR PATIENT WITH GESTATIONAL DIABETES? The incidence of subsequent overt diabetes is severalfold higher in women who have previously experienced gestational diabetes (15). O'Sullivan (16) found a 16fold greater incidence of diabetes in women who had gestational diabetes than in those who did not have diabetes during pregnancy. It has also been observed that the incidence of diabetes developing in obese gestational diabetic subjects over 10 yr was 46.7% compared
DIABETES CARE, VOL. 13, NO. 11, SUPPL. 4, NOVEMBER 1990
D.S.H. BELL AND ASSOCIATES
to 25.6% in nonobese gestational diabetic subjects (11,16).
JEFFERSON COUNTY, ALABAMA, STUDY Since 1983, we have studied gestational diabetes in the Black population. No previously reported study has specifically examined the risk factors and outcomes in American Blacks. Because there is considerable intercorrelation among risk factors, e.g., age, parity, obesity, hypertension, and a family history of diabetes, it is important to evaluate the independence of these factors with multivariable logistic regression analysis. The objectives of our study are to investigate the interrelationship of clinical, immunological, and genetic risk factors for gestational diabetes mellitus in the Black population. A long-term objective is to investigate whether these risk factors can be used to predict who will subsequently develop insulin-dependent diabetes mellitus (IDDM), non-insulin-dependent diabetes mellitus (NIDDM), or recover. The study was comprised of women who attended one of eight Jefferson County Department of Health Prenatal Clinics. Subjects diagnosed as having gestational diabetes were automatically referred to the University of Alabama at Birmingham's Complication Center for management of their pregnancy. Eighty-five percent of the clinic population was Black, and we are accumulating — 100 cases of gestational diabetes/yr. Only Black subjects with gestational diabetes were included in this study. These subjects were compared with Black control subjects who were drawn from the same clinic population and who delivered immediately after a subject with gestational diabetes and had no personal history of diabetes. From diabetic subjects at their first prenatal visit to the complications clinic and control subjects at the time of delivery, information was obtained for maternal age, maternal weight, birth weight of previous infants, obstetric history, and a family history of diabetes in a firstdegree relative. Blood was drawn for HLA typing, autoantibodies, and various restriction-fragment-length
polymorphisms (RFLPs), particularly those flanking the insulin gene and the apolipoprotein (apo) A-l and C-lll genes from both control and diabetic subjects. All values are means ± SE. The comparison of frequencies between gestational diabetic and control subjects was made by use of x2-analysis or Fisher's exact test where appropriate. The relative risk was estimated with Woolf's odd's ratio, and 95% confidence intervals were calculated. Comparison of means were conducted by use of Student's t test or analysis of variance where appropriate. Multivariable analyses were performed with logistic regression analysis. All statistical analyses were performed with the SAS statistical package. P < 0.05 was significant. Some analyses were conducted on primigravidas or multigravidas only, because the primigravidas had no previous pregnancy history information that could be included in the multivariable models.
CLINICAL OBSERVATIONS So far in our study, we have found that subjects with gestational diabetes were significantly older than the control group. Because other factors such as obesity, parity, presence of diabetes, and hypertension are age related, these significant findings had to first be exposed to multivariable logistic regression analysis before their significance was confirmed. For example, we found that there was a significant increase in multiparity in our subjects, but this was not significant after controlling for age. Similarly, the age at first pregnancy was higher in the gestational diabetic subjects than in the control subjects, but again this was found not to be significant after correcting for age. As shown in Table 1, we found no significant difference in height between diabetic and control subjects; however, we did find that the diabetic subjects were heavier (76.7 ± 1.0 vs. 62.7 ± 1.1 kg, P < 0.0001), and this was significant after correcting for age. Similarly, with the use of >120% of ideal body weight taken from the Metropolitan Life Insurance tables as a measure of obesity (1 7), we found that the diabetic subjects were
TABLE 1 Clinical observations Characteristic Age (yr) Height (m) Weight last menstrual period (kg) Obesity (>120% ideal body weight) Body mass index (kg/m2) Family history of diabetes (%) Hypertension (this pregnancy; %) Ever hypertensive (%) Family history of ischemic heart disease (%)
Cestational diabetes
Control
28.1 ± 0.3 (406) 1.6400 ± 0.0004 (347) 76.7 ± 1.0 (403) 45.3 28.7 ± 0.5 (336) 43.3 26.9 46.8 9.4 (213)
21.7 ± 0.3 (263) 1.6300 ± 0.0004 (259) 62.7 ± 1.1 (269) 17.3 23.1 ± 0.3 (247) 16.6 2.7 18.2 3.7 (73)
