Background:
GDM has steadily increased in California from 3.3% in 1997 to 6.2% in 2005. Most studies investigating the association between ethnicity and GDM have focused on major racial/ethnic groups and have not looked at rates among the diverse Asian subgroups. GDM is important because it is associated with increase risk of intrauterine fetal deaths, fetal macrosomia, maternal hypertensive disorders and cesarean delivery.

Objectives:
To determine the prevalence of GDM among California's Asian racial/ethnic subgroups.

Methods:
Cases of GDM (ICD9-CM code of 648.8x) were identified from linked birth and hospital discharge files. The study cohort included all 2002 singleton births to California mothers between 15 and 49 years of age with no pre-existing diagnosis of diabetes. Backward stepwise multivariate logistic regression was used to calculate the odds ratios (OR) and 95% confidence intervals (95% CI) for GDM.

Results:
In 2002, there were 505,117 singleton births to California mothers, age 15 to 49 years with no pre-existing diagnosis of diabetes. Five percent (25,281) were reported to have GDM. Among the Asian sub-groups, GDM prevalence was highest among Asian Indians (11%), Filipinos (9%) and Chinese (8%). Asians were two times more likely than the non-Hispanic Whites to experience GDM during pregnancy. Compared to Whites, after adjusting for socio-demographic factors, the GDM odds ratios and their 95% confidence intervals for the following Asian subgroups is as follows: Asian Indians 3.2 (2.9-3.5), Filipinos 2.3 (2.2-2.5), Thai 2.1 (1.5-2.8), Vietnamese, 1.9 (1.7-2.1), Chinese, 1.8 (1.6-1.9), Laotians, 1.3 (0.9-1.8), Cambodians 1.2 (1.0-1.6), Japanese 1.1 (0.9-1.3), and other Asians 2.1 (1.9- 2.4).

Conclusion and implications for practice:
Among resident Californians with GDM, several Asian sub-groups have a significantly higher prevalence for GDM. Within the highly diverse Asian American subgroups, Asian Indians, Filipinos, Thai, Vietnamese and Chinese were more likely to have GDM compared to Whites. Targeted screening for GDM and culturally and linguistically appropriate public health messages on preventive measures during preconception and interconception counseling should be targeted toward high-risk Asian subgroups which may assist in achieving euglycemia during pregnancy and help alleviate the poorer birth outcomes observed among women with GDM.