The gestational weight gain (GWG) guidelines of the Institute of Medicine (IOM) aim to optimize birth outcomes and reduce pregnancy complications. The GWG guidelines are set based on the prepregnancy weight status and optimal weight gain at different trimesters of pregnancy. Dietary references intakes (DRIs) of the IOM are set for each trimester of pregnancy for energy intake and other essential nutrients by age groups (≤ 18, 19-30, 31-51 years). The DRIs, however, do not take into account the differing energy and nutrient requirements of women with different prepregnancy weights. In this cross-sectional study, we tested the hypothesis that diet quality during pregnancy is associated with adequate GWG at different stages of pregnancy. Diet quality during pregnancy was assessed from a 24-h recall measured by the healthy eating index of 2005 (HEI-2005). Both GWG and diet quality data were from 490 pregnant women aged 16-43 years included in National Health and Nutrition Examination Survey 2003-2006, a program of studies designed to assess the health and nutritional status of adults and children in the US, during which pregnant women were oversampled. Logistic regression models adjusted for age, trimester of gestation, race/ethnicity, education level, marital status, family poverty income ratio, daily supplement use, physical activity, and prepregnancy BMI were used to investigate if HEI-2005 is a determinant of GWG status at different trimesters of pregnancy. We found that HEI-2005 scores were not determinants of adequate GWG, although inadequate intake of total vegetables (OR 3.8, CI 1.1-13.2, p = 0.03) and oils were associated with excessive GWG (OR 2.8, CI 1.2-6.4, p = 0.02) when covariates were controlled. Although adequate GWG was not associated with diet quality as measured by HEI-2005 during pregnancy in this study, comprehensive prenatal counseling is still important to reduce adverse birth outcomes.