Teratogenicity associated with pre-existing and gestational diabetes

To review the teratogenesis associated with pre-existing and gestational diabetes, to provide guidelines to optimize prevention and diagnosis of fetal abnormalities in women with diabetes, and to identify areas specific to fetal abnormalities and diabetes requiring further research. Pre-conception counselling, pre-conception and first trimester folic acid supplementation, and glycemic control. Increased awareness of fetal abnormalities associated with pre-existing and gestational diabetes. The Cochrane Library and Medline were searched for English-language articles, published from 1990 to February 2005, relating to pre-existing and gestational diabetes and fetal abnormalities. Search terms included pregnancy, diabetes mellitus, pre-existing diabetes, type 1 diabetes, type 2 diabetes, insulin dependent diabetes, gestational diabetes, impaired glucose tolerance, congenital anomalies, malformations, and stillbirth. Additional publications were identified from the bibliographies of these articles as well as the Science Citation Index. All study types were reviewed. Randomized controlled trials were considered evidence of the highest quality, followed by cohort studies. Key studies and supporting data for each recommendation are summarized with evaluative comments and referenced. The evidence collected was reviewed by the Genetics and Maternal Fetal Medicine Committees of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the criteria and classifications of the Canadian Task Force on Preventive Health Care. 1. Experimental studies suggest that hyperglycemia is the major teratogen in diabetic pregnancies, but other diabetes-related factors may also affect fetal outcomes. Further research using animal models is required to clarify the teratogenic factors associated with pre-existing and gestational diabetes. (II-3C) 2. Prospective and retrospective cohort studies have demonstrated an increased risk of congenital abnormalities with pre-existing diabetes. Further studies that include outcomes from first and second trimester pregnancy terminations, account for potential confounding variables, and use appropriate control groups are required. (II-2A) 3. Prospective and retrospective cohort studies have demonstrated an increased risk of congenital abnormalities with gestational diabetes. This observation is probably related to the inclusion of women with unrecognized type 2 diabetes. Clarification of the relationship between gestation