To our knowledge, this is the first investigation to document both the prevalence and the patterns of remission, continuation, and incidence of broadly defined eating disorders in a large cohort of pregnant women. In this sample, pre-pregnancy prevalence estimates were 0.1% for AN, 0.7% for BN, 3.5% for BED, and 0.1% for EDNOS-P. Due to the complications of assessing the weight criterion for AN during pregnancy, we only have prevalence data for BN, BED and EDNOS-P during pregnancy. The estimates were 0.2 % for BN, 4.8% for BED, and < 0.1% EDNOS-P. Previous reports from Norway in the general population (i.e. not selected for pregnancy), reported prevalences of 0.3 % for AN, 0.7% for BN and 1.5% for BED (Götestam and Agras, 1995
Our observed pre-pregnancy prevalence of AN is on the low end of that reported in epidemiologic investigations of women not selected on the basis of pregnancy (Hoek, 2006
). This may reflect the fact that at least some individuals with AN have impaired fertility and/or social/interpersonal deficits decreasing their likelihood of becoming pregnant (Strimling, 1984
, Weinfeld et al., 1977
, Stewart et al., 1990
), or alternatively, the stress of pregnancy in individuals with AN could make them less likely to agree to participate in a study such as MoBa.
Examining the course of eating disorders during pregnancy, we found the most common pattern for BN and EDNOS-P to be remission or partial remission of symptoms during pregnancy—with combined remission rates surpassing continuation rates for all types of BN and EDNOS-P. This suggests that for many, but clearly not all women, pregnancy is a powerful stimulus to decrease bulimic symptomatology. This can take the form of reductions in both binge eating and compensatory behavior, or in the case of those partially remitted women, elimination of compensatory behaviors only (which may be viewed as potentially more harmful to the fetus). This parallels similar observations of spontaneous quitting in pregnancy for both alcohol use and smoking (Bruce et al., 1993
, Ockene et al., 2002
, Kruse et al., 1986
, Solomon and Quinn, 2004
). Whether the observed decreases are limited to the period of pregnancy or are more lasting will be addressed in future waves of the MoBa study. In addition, although incident cases of BN during pregnancy were reported, they were rare.
Unexpectedly, we found the course of BED to be different than that of BN. For BED, continuation of symptoms during pregnancy was more common than remission. Most notably, new onsets of BED were much more common than the other eating disorders (1.12 per 1000 person-weeks) or 711 new cases in our sample. We are unaware of previous reports of incident BED during pregnancy and our finding raises the important issue of the validity of questions regarding binge eating during pregnancy. An important topic for further detailed investigation is whether the terms associated with the evaluation of binge eating (e.g. eating and unusually large amount of food, feeling out of control) are more likely to be endorsed by women who are experiencing appetite changes associated with pregnancy. The magnitude of our observed incident cases suggests that this is an important area of inquiry to determine the extent to which the reported behavior truly represents pathological eating behavior.
Although our analyses were unable to detect any demographic parameters associated with the course of BN except for smoking, for BED, new cases were associated with an array of variables reminiscent of the “matrix of disadvantage” (Mullen et al., 1993
). Women with higher BMIs during pregnancy, more previous pregnancies, at least one abortion, lower income and education, greater smoking, and whose native language was not Norwegian were more likely to report developing BED during pregnancy. Although additional data are needed to characterize these individuals more fully, from this assessment it appears that general indices of economic and social disadvantage may be associated with the development of this symptom cluster during pregnancy.
Pregnancy is a powerful biopsychosocial event. For some, pregnancy appears to be a window of opportunity for discontinuing bulimic behaviors that could be harmful to both mother and child. For a smaller number of women, however, their bulimic behaviors (binge-eating and purging) persist during pregnancy. We will explore the impact of these persistent behaviors on pregnancy outcome and child development in future waves of data analysis in this cohort.
The somewhat surprising number of incident cases of BED during pregnancy raises several questions. For these women, rather than a window of opportunity, pregnancy appears to be a window of vulnerability. Several potential explanations for the emergence of BED during pregnancy emerge. Biologically, the myriad of adaptive neuroendocrine changes that occur in pregnancy that affect multiple brain functions influencing metabolism, appetite, and mood (Russell et al., 2001
) may render pregnancy a high risk period for developing binge-eating. Behaviorally, women who fail to increase food intake according to the increased metabolic needs of pregnancy may experience unexpected and intense hunger which may lead to compensatory overeating and ultimately trigger a pattern of appetite dysregulation. This is perhaps less likely given that changes were seen relatively early in pregnancy prior to appreciable increases in metabolic requirements. Psychologically, especially given the pattern of social disadvantage associated with incident cases in this sample, the psychosocial stress of pregnancy may serve as an environmental trigger for binge eating.
These findings must be considered within the context of several limitations. First, although the diagnostic questions we used had been used in previous epidemiologic studies in Norway, they nonetheless were self-report questions and targeted broadly defined disorders. Direct diagnostic interviews may have yielded richer diagnostic information; however, given the magnitude of the sample, this was not practical. Second, although our frequency criteria for binge eating and purging differed from current DSM criteria, we emphasize that the established criteria have not been empirically supported (Sullivan et al., 1998
). Third, women may have been hesitant to admit to eating disorders behaviors during pregnancy which would have led to an underestimation of continuation rates and an overestimation of remission. Fourth, BMI measures were self-report rather than measured—a common approach given the logistical complications and cost of measured weight in larges samples such as MoBa. Although there are no comparable data from Norway, data from other large samples suggest a correlation of 0.94 between measured and self-reported height and 0.98 between measured and self-reported weight for women (Bulik et al., 2001
). Fifth, 42% of women invited agreed to participate in MoBa. Although this response rate is low, it is not uncommon to large epidemiologic studies and does not necessarily imply a biased sample (Hartge, 2006
). The determination of bias is complex and would occur if and only if individuals who chose not to participate in this study differed markedly from those who did participate on the variables of interest. Initial comparisons of the MoBa cohort to the Norwegian population indicates lower rates of preterm birth (7.2% vs 7.7%) and low birth weight (< 2500g) (4.6 % vs 5.1%) possibly reflecting a socioeconomic gradient associated with participation (Magnus et al., 2006
). Further exploration of this using education data suggests that the MoBa participants may be somewhat more educated than the general Norwegian population with 58% attending some form of college in comparison to 46% of women between 25-29 years and 43% of women between 30-39 years reported to have higher education in 2005 by Statistics Norway. Finally, our data reflect changes in eating disorders symptomatology in the early stages of pregnancy. It is possible that such changes may not reflect patterns of remission, continuation, and incidence across the entire gestational period.
Nonetheless, our results point to additional questions and cautions. Using data that are currently being collected, in future papers we will explore personality and psychiatric features that are associated with remission, continuation, and incidence of eating disorders during pregnancy. Clinically, given that some data suggest that women who have eating disorders are unlikely to report them to their obstetricians (Lemberg and Phillips, 1989
), our results suggest that physicians, nurses, and midwives working with pregnant women should be alert to the possibility of enduring and emergent eating disorder symptoms. For women with known eating disorders, the onset of pregnancy does not necessarily ensure discontinuation of symptoms, and regular follow-up regarding persistence of symptoms should be considered. Moreover, as part of routine prenatal inquiries about nutrition, health care providers should also ask about the presence of binge eating. As we do not yet know the impact of binge eating during pregnancy, detection is a minimum first step that could facilitate referral for appropriate intervention if clinically indicated.