Treatment of gestational diabetes reduces serious perinatal morbidity, Caroline A. Crowther, M.D., of the University of Adelaide (Australia) and her associates reported.
Although the risks associated with gestational diabetes mellitus (GDM) are well recognized, it has been uncertain whether screening and treatment to reduce maternal glucose levels reduces these risks. Given this uncertainty, professional groups disagree on which patients should be screened, the investigators said (N. Engl. J. Med. 2005;352:2477–86).
Now, new investigation findings in favor of screening come from the 18-center Australian Carbohydrate Intolerance Study in Pregnant Women (ACHOIS) in which serious perinatal complications occurred in just 1% of the infants of 490 women with GDM who were randomized to intensive glucose management, compared with 4% of 510 women who received routine care.
In an accompanying editorial, Michael F. Greene, M.D., and Caren G. Solomon, M.D., wrote that “this study provides critical evidence that identifying and treating [GDM] can substantially reduce the risk of adverse perinatal outcomes without, at least in this trial, increasing the rate of cesarean delivery.”
However, Dr. Greene and Dr. Solomon, both on the editorial board of the New England Journal of Medicine, noted that the study leaves unanswered the question of what level of blood glucose warrants routine intervention (N. Engl. J. Med. 2005;352:2544–6).
The study included women with a singleton or twin pregnancy between 16 and 30 weeks' gestation who had at least one risk factor for GDM on selective screening or a positive 50-g oral glucose challenge test, with a 1-hour postchallenge glucose level of at least 140 mg/dL followed by a 75-g oral glucose tolerance test at 24–34 weeks' gestation in which venous plasma glucose was less than 140 mg/dL after an overnight fast and 140–198 mg/dL at 2 hours.
When the study began, these women had been classified as having glucose intolerance of pregnancy by the World Health Organization, but during the course of the study (in 1998) WHO began classifying any glucose level above normal as being GDM. Women whose glucose values exceeded these cutoffs were not included in the study.
The women randomized to intensive intervention were informed of their diagnosis. They received dietary counseling and were taught how to perform self-blood glucose monitoring, with targets of no more than 99 mg/dL premeal and 126 mg/dL 2 hours after eating. Twenty percent received insulin therapy. The women randomized to routine care were told they did not have GDM, according to Dr. Crowther and her associates.
Serious perinatal outcomes, including death, shoulder dystocia, bone fracture, and nerve palsy, occurred in 1% of the intervention group vs. 4% of the routine care group after adjustment for maternal age, race/ethnicity, and parity. Thus, 34 mothers would need to be treated to prevent one serious outcome in an infant, they said.
Women in the intervention group were significantly more likely to have induction of labor (39% vs. 29%), but the rates of cesarean delivery were similar (31% vs. 32%), as were the reasons for it. Infants in the intervention group also had fewer admissions to the neonatal nursery (71% vs. 61%). At 3 months' post partum, fewer women in the intervention group had a score on the Edinburgh Postnatal Depression Scale suggestive of depression (8% vs. 17%); anxiety scores were similar.
Among the secondary outcomes, there were no perinatal deaths among the infants from the intervention group, but three stillbirths and two neonatal deaths occurred among infants in the routine care group. There were no differences in the rates of shoulder dystocia between the two groups. No bone fractures or nerve palsies occurred in the intervention group; the routine care group had one of the former and three of the latter.
Birth weights were significantly lower among the infants born to women in the intervention group (3,335 g vs. 3,482 g), and they were also born at an earlier gestational age, which makes sense given their higher rate of induction of labor. Significantly fewer infants in the intervention group were large for gestational age (13% vs. 22%), and fewer had macrosomia, defined by a birth weight of 4 kg or greater (10% vs. 21%).
Women in the intervention group made fewer prenatal clinic visits after enrollment than did the routine care group, but they made more visits to the physician. Weight gain was less in the intervention group, and fewer women were diagnosed with preeclampsia. The rates of prenatal hospital admissions were similar.
Dr. Greene and Dr. Solomon agreed with the authors' justification for having randomized one group of women to no treatment—that before this study there were no conclusive data regarding the effects of treating GDM, even after the WHO definition was revised.