OAKLAND, Calif., Nov. 11, 2013 /PRNewswire/ -- Pre-pregnancy obesity and older maternal age are among the risk factors for delayed lactation for women with gestational diabetes mellitus, according to a Kaiser Permanente study in The American Journal of Clinical Nutrition. (Logo: http://photos.prnewswire.com/prnh/20130718/SF49717LOGO) The study analyzed 883 racially and ethnically diverse women to assess the incidence of delayed milk production among women with a history of GDM, or diabetes during pregnancy, and to determine whether pre-pregnancy weight was an independent risk factor even after the severity of their GDM was taken into account. The women were enrolled between September 2008 and March 2011 in the Study of Women, Infant Feeding and Type 2 Diabetes (SWIFT), an ongoing study of Kaiser Permanente Northern California members who experienced a diagnosis of gestational diabetes. Delayed onset of lactation was reported by 33 percent of the women, and was associated with pre-pregnancy obesity, older maternal age and insulin treatment for GDM (which is indicative of greater severity of gestational diabetes). "Given the potential for breastfeeding to mitigate the higher risk that women with GDM face for developing type-2 diabetes, skilled lactation support is particularly important for obese women with GDM," said lead author Susana L. Matias, PhD, a postdoctoral researcher at the Kaiser Permanente Division of Research and the University of California, Davis, Department of Nutrition. Among the study group, the average pre-pregnancy body mass index was 29.3, falling within the "overweight" category. GDM is associated with higher pre-pregnancy weight. However, even in this population, being in the heaviest BMI category (i.e., "obese") increased the risk for delayed onset of lactation. Insulin resistance, also associated with obesity, may be another possible mechanism linking obesity and delayed onset of lactation.