LISBON — Pregnant women with serum glucose levels as low as 7.8 mmol/L 2 hours following an oral glucose tolerance test should be diagnosed with gestational diabetes, according to results from two independent studies.
Our data “make it hard to ignore 'mild' gestational diabetes,” Dr. Daghni Rajasingam said at the annual meeting of the International Society of Obstetric Medicine. She and her associates reviewed the outcomes of 184 pregnant women seen at St. Thomas' Hospital, London, who had a serum glucose level of 7.8–8.9 mmol/L 2 hours after an oral glucose tolerance test (OGTT) at 28 weeks' gestational age, and found a high incidence of cesarean sections and macrosomia.
The second study, conducted in Australia at the Royal North Shore Hospital in Sydney, reviewed 478 women with a serum glucose level of at least 7.8 mmol/L 2 hours after an OGTT and compared treated and untreated subgroups of these women with a comparator group with no gestational diabetes. Again, the results showed untreated, mild gestational diabetes led to a higher rate of adverse outcomes.
“Our results support the conclusions of the Australian Carbohydrate Intolerance Study in Pregnant Women [ACHOIS],” Dr. Michelle H. Kwik, an ob.gyn. at Royal North Shore Hospital, said at the 15th World Congress of the International Society for the Study of Hypertension in Pregnancy.
ACHOIS established the efficacy of diabetes intervention—dietary advice, blood glucose monitoring, and insulin therapy when needed—in pregnant women, while defining gestational diabetes as a serum glucose level of 7.8–11.0 mmol/L 2 hours after an OGTT (N. Engl. J. Med. 2005;352:2477–86). This definition, endorsed by the World Health Organization, uses a minimum serum glucose level significantly lower than the 8.6 mmol/L minimum the American Diabetes Association adopts.
The goal of both of the new studies was to examine whether women with serum glucose levels as low as 7.8 mmol/L have complications consistent with more severe gestational diabetes.
The St. Thomas' Hospital study reviewed the outcomes of women who were treated there during April 2002-July 2005. The outcomes of the 184 women with mild gestational diabetes were compared with those of a group of pregnant women without gestational diabetes seen at the hospital at the same time, and with the intervention and controls groups from the ACHOIS trial.
The incidence of induced labor in the mild diabetes group at St. Thomas' Hospital was 18%, not much higher than that of the normal women there (15%), and less than the intervention and control groups in ACHOIS (28% and 38%, respectively). But for the two other criteria examined, the mild diabetes group had a substantially higher rate of complications.
The cesarean section rate was 39% in the mild diabetes group, compared with 25% in the healthy group. And the macrosomia rate was 20% in newborns in the mild diabetes group, compared with 9% in the healthy group, reported Dr. Rajasingam, an ob.gyn. at St. Thomas' Hospital. More than 60% of the cesarean deliveries in the women with mild diabetes were emergency deliveries.
Use of a more restrictive definition of gestational diabetes, with a higher minimum glucose level, had been driven by the difficulty of providing gestational-diabetes care to a larger number of women. But the new finding showed all women with a serum glucose level of at least 7.8 mmol/L 2 hours after an OGTT need more intensive prenatal care, Dr. Rajasingam said.
The Royal North Shore Hospital study reviewed three groups of pregnant women who were seen there during February 2000-May 2005. The untreated group included 213 women with a normal fasting serum glucose level, but with a serum level of at least 7.8 mmol/L 2 hours after an OGTT.
A second group (those who received treatment) included 265 women with an OGTT serum level of at least 7.8 mmol/L as well as an abnormally high fasting glucose level. Treatment consisted of dietary counseling for 182 of these women and insulin treatment for the other 83. The third group, the comparison group, included 197 women who failed a 50-g glucose challenge test, but whose serum glucose was less than 7.8 mmol/L 2 hours after an OGTT.
The study's primary outcomes were the incidence of macrosomia, defined as a birth weight greater than the 90th percentile, and the incidence of shoulder dystocia. The incidence of macrosomia was 15% in the comparison group, 23% in the untreated group, and 12% in the treated group. Shoulder dystocia occurred in 1% of comparison deliveries, 5.2% of untreated deliveries, and 2.6% of treated deliveries. For both outcomes, the difference between the roups was statistically significant.