the attitude score was not significantly related to GWG. The investigators also reported that maternal attitude toward weight gain was influenced by prepregnancy BMI, with thin women tending to have positive attitudes and obese women negative attitudes about GWG. Taken together, the evidence is inconclusive regarding the influence of maternal attitude on actual GWG.

For the majority of women, weight loss during pregnancy is discouraged. However, a small percentage (8.1) of women reported in the Behavioral Risk Factor Surveillance Survey (BRFSS) that they attempted to lose weight during pregnancy (CDC, 1989, 1991). Another survey of women who reported being pregnant and also trying to lose weight indicated that prevalence of weight loss behavior during pregnancy occurred among those who reported drinking and smoking (12.7 percent), women in the first trimester of pregnancy (9.4 percent), those who were diabetic (9 percent), and those with very high BMIs (6.9 percent) (Cogswell et al., 1996). Cohen and Kim (2009) reviewed aggregated multiple year data between 1996 and 2003 from the BRFSS (1989) and found weight-loss attempts during pregnancy were more frequent among women over 34 years of age (6.2 percent) and Hispanic women (13.1 percent). Carmichael et al. (2003) reported in a population-based case-control study of 538 cased and 539 control infants that restricted food intake or fad dieting by the mother during the first trimester of pregnancy was associated with significant risk for neural tube defect among both food restrictors (OR = 2.1, 95% CI: 1.1-4.1) and dieters (OR = 5.8, 95% CI: 1.7-10) compared to controls. Interestingly, no significant increased risk for neural tube defect was detected for dieting behaviors during the 3 months prior to conception.

Behavioral Factors

The committee considered several behavioral factors likely to have an impact on GWG: dietary intake and physical activity (i.e., the two primary components of energy balance, with dietary intake approximating energy expenditure); substance abuse (including cigarette smoking, alcohol use, and drug use); and unintended pregnancy.

Dietary Intake

Numerous clinical trials have examined the effects of either caloric supplementation or restriction on GWG. In a systematic review of 10 trials, Kramer and Kakuma (2003) found that balanced energy/protein supplementation was associated with modest increases in GWG. In contrast two trials reviewed in Kramer and Kakuma (2003) among women who were obese (Campbell, 1983) or had high GWG (Campbell and MacGillivray,

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