Psychosocial Factors & Dietary Adherence

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By Susan E. Waisbren, Ph.D.

Adherence to medical recommendations in maternal phenylketonuria (PKU) ought to be a straightforward process. Women considering pregnancy need only initiate the diet, monitor their blood phenylalanine (Phe) levels, adjust their Phe intake accordingly, and when their metabolic control is adequate, stop birth control and conceive. In reality, the level of adherence to medical recommendations in maternal PKU defies our worst predictions and fears. Naïve assumptions about human behavior lead us to believe that people, if given proper information, will do what needs to be done in order to protect their future children.

In maternal PKU, and probably in PKU as well, models for understanding acceptance or avoidance of positive health behaviors apply. The Theory of Reasoned Action (Ajzen, Fishbein, 1980) postulates that intentions to act are a function of "subjective norms" (expectations by important others) and "attitudes toward the behavior." An extension of this theory, the Theory of Planned Behavior, adds a third dimension, "manageability" (Ajzen, 1988; Ajzen, 1991). Accordingly, individuals with PKU will be more likely to adhere to medical recommendations and follow the Phe-restricted diet if (1) there is social support for them to adhere to medical recommendations and follow the diet; (2) they have positive attitudes about the diet and believe in its efficacy; and (3) the treatment is manageable in their daily lives.

Fifteen years ago, we initiated a psychosocial study of maternal PKU. We developed a model of psychosocial development in which each stage in the maternal PKU life cycle is associated with a particular treatment goal. The stages include (1) consistent birth control use to prevent unplanned pregnancies, (2) formation of a reproductive decision, (3) diet initiation for pregnancy, and (4) diet continuation during pregnancy. Sixty-nine women with PKU, 68 of their acquaintances, and 69 women with diabetes were interviewed annually for 5 years. For the women with PKU, social support and attitudes were significantly associated with adherence to medical recommendations at the stages of prevention of unplanned pregnancy, treatment initiation, and diet continuation throughout pregnancy (Waisbren, Shiloh, St. James, et al., 1991; Waisbren, Hamilton, St. James, et al., 1995). Interventions that focus on improving social support networks and attitudes toward treatment may increase adherence to medical recommendations.

Thereafter, we established the PKU Community Outreach Resource Programs (PKU CORPS) to develop specific interventions for women with PKU. For 5 years, a maternal PKU camp provided education and social support for young women with PKU. The curriculum combined educational and recreational activities aimed at instilling social support and enhancing positive attitudes regarding treatment for maternal PKU. Subjects for a study conducted during the fifth camp year included 25 young women, ages 11 to 32 years. The mean blood Phe concentrations of the subjects were significantly reduced by 37 percent by the end of camp, with 96 percent (24 of 25) of the campers lowering their levels. Forty-eight percent of the campers had concentrations below 10 mg/dL at the end of camp, compared with 12 percent on the first day of camp. There were significant increases in scores on tests of knowledge of maternal PKU and the maternal PKU diet. There was a significant increase in the campers’ ratings of the degree to which they perceived other people wanting them to use birth control if they were sexually active. Returning campers had a significantly greater increase in their social support networks after camp than did new campers. On followup, the most recent blood Phe determinations reflected a 20 percent reduction in precamp levels. One woman attained metabolic control before becoming pregnant following the end of the camp. As much as 96 percent of the campers were still in contact with at least one other camper, with the mean number of contacts being 7.84 (Waisbren, Rokni, Bailey, et al., 1997).

The Maternal PKU Resource Mothers Program was a second social support program sponsored by the PKU CORPS. Resource Mothers are mothers of children with PKU. Since these women have children with PKU, they are familiar with the diet, the methods of calculating Phe in food, and the stresses and strains such restrictions produce on a family. The Resource Mothers explain the issues of maternal PKU, help pregnant women obtain prenatal care, purchase appropriate foods or pregnancy-related items, plan and cook meals, and arrange transportation to doctor appointments. They provide emotional support and maintain communication with the metabolic center. They are paid a stipend for time spent in training and supervision and for their visits to the young women.

A recently completed nonrandomized study of the Resource Mothers Program (St. James, Shapiro, Waisbren, 1999) compared 19 pregnancies in women with PKU who received the services of a Resource Mother with pregnancies in 66 women with PKU, enrolled in the Maternal PKU Collarborative Study (MPKUCS), who did not have a Resource Mother. The results indicated that the pregnant women who had Resource Mothers achieved metabolic control at a mean of 8.5 weeks, compared with a mean of 16.1 weeks for those in the comparison group. At 1 year of age, infants whose mothers had a Resource Mother had a mean developmental quotient (DQ) of 108, and the mean DQ of the control group was 95.

Although the study suggests promising results from this type of home visitation program, a number of factors may have confounded the results. Only the women in the Resource Mothers group had been enrolled in a previous study in which they had annual visits from professionals, and many had also attended the maternal PKU camp. Data from the comparison group were retrospective and had been obtained 5 to 10 years previously, when recommendations for dietary control were not as strict. Finally, assignment to groups was not randomized.

Currently, a randomized clinical trial of the Resource Mothers Program is under way in six metabolic centers. More than 100 pregnancies will be randomly assigned to the group with or without Resource Mothers. The most recent MPKUCS analyses document the continued problem of late-treated pregnancies. The MPKUCS also found, however, that a stimulating home environment during the first year of the offspring’s life may attenuate the adverse effects of maternal PKU (Waisbren, Chang, Levy, et al., 1998). Thus, a home visitation program only during pregnancy, the original plan for the Resource Mothers Program, is unlikely to be optimally effective. Accordingly, the current project now includes outreach before pregnancy to all adolescent girls and young women tracked by the metabolic centers and to all families after a baby is born. Only those randomized to the treatment group receive the services of a Resource Mother during pregnancy. The research question is whether the Resource Mothers Program yields benefits beyond what are provided by basic metabolic services, as well as outreach before and after pregnancy.

Adolescent females will be targeted for health education outreach programs. Information about maternal PKU will be provided to the patients tracked by each clinic and to their primary care physicians. School-based health centers will be contacted about the needs of young women with PKU and the risks of maternal PKU. A Web site is being established. Public discussions are under way with officials at the Department of Public Health in Massachusetts regarding the possibility of having maternal PKU listed as a risk factor on the confidential section of birth certificates. This would trigger followup from the Department of Public Health and automatically qualify the child for early intervention.

Adherence to medical recommendations in maternal PKU no longer appears to be a straightforward process. A comprehensive system of care that includes programs to enhance social support, engender positive attitudes, and increase the manageability of treatment requires integrated services and adequate financial support. At this time, with the conclusion of the MPKUCS, the infrastructure for maternal PKU treatment is at best precarious, and the will to set aside funds for broadly focused programs may be lacking. Research must focus on continuity of care, because no single program or intervention will address the multitude of challenges facing women with PKU.


  • Ajzen I. Attitudes, personality and behavior. Milton Keynes (UK): Open University Press; 1988.
  • Ajzen I. The theory of planned behavior. Organ Behav Hum Decis Process 1991;50:179-211.
  • Ajzen I, Fishbein M. Understanding attitudes and predicting social behavior. Englewood-Cliffs (NJ): Prentice-Hall; 1980.
  • St James PS, Shapiro E, Waisbren SE. The Resource Mothers Program for maternal phenylketonuria. Am J Public Health 1999;89:762-4.
  • Waisbren SE, Chang P, Levy HL, Shifrin H, Allred E, Azen C, et al. Neonatal neurological assessment of offspring in maternal phenylketonuria. J Inher Metab Dis 1998;21:39-48.
  • Waisbren SE, Hamilton BD, St James PJ, et al. Psychosocial factors in maternal phenylketonuria: women’s adherence to medical recommendations. Am J Public Health 1995;85:1636-41.
  • Waisbren SE, Rokni H, Bailey I, Rohr F, et al. Social factors and the meaning of food in adherence to medical diets: results of a maternal phenylketonuria summer camp. J Inherit Metab Dis 1997;20:21-7.
  • Waisbren SE, Shiloh S, St James P, Levy HL. Psychosocial factors in maternal phenylketonuria: prevention of unplanned pregnancies. Am J Public Health 1991;81:299-304.

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