Consuming a healthy diet in pregnancy has the potential to improve obstetric outcome, including minimizing the risk of macrosomia, especially for pregnant women with gestational diabetes mellitus or obesity.

The benefits of low Glycemic Index diets

A recent review found some evidence to support the use of low GI diets, defined by the consumption of carbohydrates that release glucose gradually, in women with gestational diabetes mellitus, although it is less clear whether they could also benefit nondiabetic women¹. Two studies^2;3, which included women with a range of body weights, suggest that dietary glycaemic control may benefit both normal and overweight women, although there are some concerns over ensuring adequate foetal growth particularly in normal weight women⁴.

Another study investigating overweight and obese pregnant women found that a low glycaemic load diet (i.e. foods with low values on an index that accounts for both GI value and carbohydrate content) improved cardiovascular risk factors, lengthened pregnancy duration and increased infant head circumference⁵.

Psychological predictors of intentions of pregnant women to improve gestational diet

Reducing GI relies on changing dietary behavior in pregnant women. Behaviour change is often portrayed as a consequence of changes in psychological variables: modifying knowledge, attitudes and beliefs influence intentions⁶ which in turn influences behaviour⁷. However, interventions designed to improve diet in pregnancy, including those designed specifically to lower GI or glycaemic load^3;5 have neglected psychological changes.

The present study assessed pregnant women’s attitudes and motivations concerning intake of high saturated fat, high-sugar foods, and fruit and vegetables (F&V), and aimed to model psychological predictors of intentions to consumer healthier quantities of these foods over the remainder of the pregnancy term. The analysis draws on variables from the Health Belief Model (HBM): threat perceptions and behavioural evaluations⁸ augmented by a measure of perceived social approval (i.e. ‘subjective norms’⁹).

Participants were given a questionnaire. One hundred and three pregnant women completed questionnaire measures of intentions to modify the consumption of the target foods, current intake, perceived vulnerability to and severity of adverse outcomes of unhealthful consumption to these foods (i.e.’threat’), benefits of dietary change to mother and baby, barriers to dietary changes, and social approval for dietary change (‘subjective norms’).

Current intake or behavior was estimated based on the perceived adequacy of current dietary intake. Intention items measured the intention to eat more healthily over the rest of the pregnancy, and participants intending to eat less healthily were excluded from respective analyses; perceived benefits related to positive outcomes for mother and baby. Perceived barriers were as follows: barriers to consuming F&V related to difficulty of access and preparation, and cost; barriers to reducing fat consumption related to high-fat foods being easy to cook, satisfying cravings and helping deal with stress; barriers to reducing sugar-consumption related to high-sugar foods satisfying cravings and helping deal with stress. For each behavior, subjective norms items focused on anticipated approval from family and healthcare professionals, respectively.

A cross-sectional design was used.

Current behaviour and intentions were negatively correlated for each behaviour

Participants who reported excessive current intake of high-fat and high-sugar foods were more likely to intend to reduce the intake of these foods and participants who felt they ate ‘too little’ F&V had stronger intentions to increase F&V consumption. Perceived benefits for mother and baby enhanced intentions to eat more F&V and eat less high-fat, and marginally significantly increased high-sugar reduction intentions. Lack of effects for barriers, threat and subjective norms may indicate that pregnant women discount barriers to health-promoting behavior, understand the threat posed by unhealthy eating and perceive social approval form others. Dietary change interventions for pregnant women should emphasize likely positive outcomes for both mother and child. Notwithstanding some limitations (cross-sectional design, data based on self-report, representativeness and modest size of the sample), the results offer some insight into the health beliefs and dietary choices of pregnant women. Best practice for diet modification in pregnancy is likely to require the adoption of health promotion strategies to target the underlying psychological determinants of gestational diet.

BASED ON: Gardner B., Croker H., Barr S., Briley A., Poston L. & Wardle J. on behalf of the UPBEAT Trial. (2012) Psychological predicators of dietary intentions in
pregnancy. J Hum Nutr Diet.