Introduction
Gestational diabetes and pregnancy-related hypertension can lead to adverse health effects in mothers and infants. We assessed recent trends in the rates of these conditions in Los Angeles County, California.

Methods
Hospital discharge data were used to identify all women aged 15–54 years who resided in the county, had a singleton delivery from 1991 through 2003, and had gestational diabetes or pregnancy-related hypertension listed as a discharge diagnosis at the time of delivery. The prevalence of each condition was calculated by calendar year, race/ethnicity, and age group. Temporal trends in the rates were assessed by using negative binomial regression models, controlling for race/ethnicity and age. Separate models were run for each racial/ethnic and age group.

Results
The age-adjusted prevalence of gestational diabetes increased more than threefold (from 14.5 cases per 1000 women in 1991 to 47.9 cases per 1000 in 2003). The age-adjusted prevalence of pregnancy-related hypertension also increased (from 40.5 cases per 1000 in 1991 to 54.4 cases per 1000 in 2003). In the multivariable regression analysis, the annual rate increase for gestational diabetes was 8.3% overall and was highest among Hispanics (9.9%). The annual rate increase for pregnancy-related hypertension was 2.8% overall and was highest among blacks (4.8%).

Conclusion
The rates of gestational diabetes and pregnancy-related hypertension are increasing in Los Angeles County. Further research is needed to determine the causes of the observed increases and the growing racial/ethnic disparities in those rates.