About 10% of women with gestational diabetes mellitus (GDM) will have the autoantibody markers for Type 1 autoimmune diabetes. From Nillson et al (2007): “The autoimmune process that leads to the development of Type 1 diabetes probably begins several years before the disease. The increased insulin resistance during pregnancy leads to an increased demand on the remaining and affected beta cells. A pregnancy could therefore uncover an early stage of Type 1 diabetes and be interpreted as just GDM.” Women may develop classical type 1 diabetes during and/or after their pregnancy or may develop latent autoimmune diabetes of adulthood (LADA) some years post-pregnancy. The correct treatment for Type 1 diabetes/LADA is exogenous insulin as early as possible, to control glucose levels, prevent further destruction of residual beta cells, reduce the possibility of diabetic complications, and prevent death from diabetic ketoacidosis (DKA). Pregnant women with autoimmune gestational diabetes should be treated with exogenous insulin to avoid maternal and fetal complications, including fetal death.
Despite 1 in 10 cases of GDM being autoimmune, in the United States and Canada, literature about gestational diabetes mellitus (GDM) typically refers to insulin resistance and the probability that a woman will at some point in her life develop Type 2 diabetes. The Canadian Diabetes Association states, “Women who have had GDM are at increased risk of developing subsequent type 2 diabetes later in life” and makes no mention of the increased risk of Type 1 diabetes. However, in Europe, educational materials almost always mention that GDM places a woman at risk for either Type 1 or Type 2 diabetes. The European medical community has long recognized that some women who have gestational diabetes are subsequently diagnosed with Type 1 diabetes. As reported in the August 1998 issue of Diabetes Forecast, in a German study 43 percent of women who developed gestational diabetes went on to have full-blown Type 1 diabetes. They were antibody positive, and they had not been diagnosed with diabetes prior to pregnancy. The British Diabetes Association, Diabetes UK, states, “About five to ten percent of women with GDM develop Type 1 diabetes sometime in their life. These women have a slowly developing form of Type 1 that is ‘unmasked’ during pregnancy.” A recent article published by Italian researchers states, “We need to bear in mind that older patients might conceivably develop adult-onset Type 1 diabetes during or after pregnancy.” In the United States, autoimmune gestational diabetes is generally ignored by the American Diabetes Association, although it is mentioned in The Type 1 Diabetes Sourcebook (ADA/JDRF, 2013; “GDM currently affects ~7% of pregnancies and 5-10% of affected women diagnosed with T2D after delivery (and some are diagnosed with autoimmune T1D, as well).”). Also, the ADA website states, “In a few women, however, pregnancy uncovers type 1 or type 2 diabetes. It is hard to tell whether these women have gestational diabetes or have just started showing their diabetes during pregnancy. These women will need to continue diabetes treatment after pregnancy.” If you ask women on TuDiabetes.org with Type 1 diabetes, many developed diabetes during pregnancy, and a large number of women on the Facebook LADA Support Group developed Type 1 diabetes/LADA during pregnancy. Mary Tyler Moore, International Chair of JDRF, was diagnosed with Type 1 diabetes after a miscarriage at age 33. Why is there this disconnect--why do the U.S. and Canada ignore autoimmune gestational diabetes? It is important to identify a woman with autoimmune gestational diabetes, to prevent the severe maternal and fetal complications of Type 1 diabetes developing in pregnancy.
An article in the July 2007 issue of Diabetes Care indicated that autoimmune gestational diabetes (new onset Type 1 diabetes) accounts for about 10 percent of all Caucasian women diagnosed with gestational diabetes. In a study of Sardinian women (Reproductive Biology and Endocrinology, 2008), 40 percent of women with GDM were antibody positive (GAD, IAA, and/or IA-2) and had autoimmune gestational diabetes. (Sardinia has the second highest prevalence of Type 1 diabetes in the world, after Finland).
Sadly, in the U.S. and Canada many women with autoimmune gestational diabetes go for months if not years with wrong diagnoses, struggling to get appropriate treatment for the disease they have (Type 1 diabetes).
What are signs that you may have autoimmune gestational diabetes? If you are slim and require insulin during pregnancy to control your GDM, it is likely that you have autoimmune gestational diabetes. What can you do? Get autoantibody testing (GAD, ICA, IA-2, IAA, ZnT8), which is relatively low cost and is a definitive test for Type 1 autoimmune diabetes (if a woman has been diagnosed with diabetes and is positive for any one autoantibody, she has Type 1 autoimmune diabetes). An article in the August 2007 issue of Diabetes Care concludes that, “Autoantibody screening in pregnant women with GDM and follow-up after delivery should be considered for early recognition of Type 1 diabetes.”
The Type 1 Diabetes Sourcebook. Anne Peters, MD, and Lori Laffel, MD, MPH, Editors. American Diabetes Association/JDRF, 2013.
Charlotta Nilsson, MD, et al. Presence of GAD Antibodies During Gestational Diabetes Mellitus Predicts Type 1 Diabetes. Diabetes Care 30: 1968-1971, 2007.
Barbara Bonsembiante, et al. Adult-Onset Type 1 Diabetes and Pregnancy: Three Case Reports. Hindawi Publishing Corp, Case Reports in Medicine. Article ID 920861, 2013.
H. Wucher et al. Poor prognosis of pregnancy in women with autoimmune type 1 diabetes mellitus masquerading as gestational diabetes. Diabetes & Metabolism, 2010.
A Lapolla, et al. Diabetes related autoimmunity in gestational diabetes mellitus: is it important? Nutr Metab Cardiovasc Dis, November 2009.