protein foods, folate, vitamin C, iron, and zinc, compared to the dietary intake of white non-Latinas and U.S.-born Latinas. Other researchers have also documented increased risk for adverse birth outcomes, including preterm birth and low birth weight, among U.S.-born women compared to foreign-born women of the same ethnic origin (Ventura and Taffel, 1985; Scribner and Dwyer, 1989; Cabral et al., 1990; Kleinman et al., 1991; Rumbaut and Weeks, 1996; Singh and Yu, 1996; Fuentes-Afflick and Lurie, 1997; Jones and Bond, 1999; Callister and Birkhead, 2002; Baker and Hellerstedt, 2006). However, most of these studies do not report GWG, and so the contribution of GWG to adverse outcomes is unknown.
Although many researchers have studied the impact of GWG advice on actual weight gains and although the U.S. Public Health Service Expert Panel on the Content of Prenatal Care recommended that pregnant women receive advice on gaining an appropriate amount of weight during pregnancy, the influence of weight gain advice on GWG has not been conclusively demonstrated (HHS, 1989). Several intervention studies have been conducted using nutrition advice alone (Orstead et al., 1985; Bruce and Tchabo, 1989) or such advice linked with home visits by nutritionists and supplemental food (Rush, 1981; Bruce and Tchabo, 1989), a nurse home visitation program (Olds et al., 1986), and the provision of prenatal care through multidisciplinary rather than traditional clinics (Morris et al., 1993). In three of the studies (Rush, 1981; Olds et al., 1986; Morris et al., 1993) the differences in mean GWG between intervention and control groups were not statistically significant. In two other studies (Orstead et al., 1985; Bruce and Tchabo, 1989) intervention groups gained significantly more weight than the control groups; however, the findings may be limited by gestational age bias. Additionally, most of these studies reported only mean GWG with no comparisons among different categories of pregravid BMI, further limiting interpretation of the findings. Brown et al. (1992) developed a prenatal weight gain intervention program based on social marketing methods; while circumstances arose that hampered full evaluation of the program, preliminary evidence suggests that GWG and birth weight of African Americans in the intervention group did not differ significantly from those of whites, while both weight gain and birth weight were significantly lower in African Americans than in whites in the control group.
Hickey (2000) identified several potential problems with the validity of previous studies on prenatal weight gain advice and actual GWG. These include, in addition to differences in pregravid nutritional status and BMI, issues such as self-selection bias, recall bias, differences in time during gestation when nutrition advice was given, variation in content and frequency of advice, the pairing of advice with other food or nonfood interventions,