Eating Disorders in Pregnancy: The Norwegian Mother and Child Cohort Study (MoBa)

Published: May 25, 2014

Recently, our group was invited to write a paper summarizing the research we have been conducting on eating disorders in pregnancy using data provided through the Norwegian Mother and Child Cohort Study (MoBa). We were excited at the opportunity to take stock of our research, which has been published in a range of journals, including Obstetrics and Gynecology, Psychological Medicine, and Maternal and Child Nutrition.

The first step was to gather the published studies – 17 were counted! As lead writer of this review – this was going to be a more monumental task than I had thought. The next step was to organize the studies into topics and to summarize the findings. The findings will be broken up into several blog posts, this first entry will cover why we decided a population-based dataset could be helpful for advancing science, and what we discovered about the prevalence and course of eating disorders in pregnancy.

First, a brief background on MoBa is necessary. MoBa (which stands for ‘Mother’ and ‘Baby’) is a population-based pregnancy cohort study that was established to investigate causes of different diseases. The study is conducted by the Norwegian Institute of Public Health and the target population was all women giving birth in Norway. Women were recruited from 1999 to 2008 and MoBa now includes 114,500 children, 95,200 mothers, and 75,200 fathers. Surveys have been administered at the following time-points: during pregnancy, at 6 months, 18 months, 3 years, 5 years, 7 years, and 8 years after birth, and surveys continue to be collected.

medium_107729240Science on eating disorders in pregnancy prior to the 2000s was insightful, but limited. There were questions about whether eating disorders in pregnant mothers led to a higher risk of adverse birth outcomes, whether pregnancy yielded a window for recovery as mothers established a health-promoting environment for the unborn baby, and how women with eating disorders felt about weight gain during and after pregnancy. There were only isolated reports, on topics such as delayed detection of pregnancy in anorexia nervosa, sudden maternal death in pregnancy, and possible impacts of eating disorders on breastfeeding. We desperately needed population-based research to provide reliable confirmation of these reports.

What are the advantages of population-based research? It considers questions of association – for instance eating disorders and birth outcomes – by looking at the associations in a large group of people, rather than seeing isolated instances that may or may not have anything to do with the underlying eating disorder. Also, population-based research allows us to identify all cases of eating disorders, in contrast to research on clinical samples, which only reports on those individuals who have actively sought treatment. This introduces a bias into the sample as they may represent more severe cases only or some other variable that leads one to be more likely to seek treatment. Finally, only through population-based research can an understanding of how common eating disorders are during pregnancy, or other factors that one might be interested in, be gained.

The first MoBa study on eating disorders in pregnancy was published in 2007, and provided estimates for how common eating disorders were during pregnancy, and the typical course of illness from pre-pregnancy through pregnancy. During pregnancy, 1 in 21 women surveyed had an eating disorder, with prevalence corresponding to 5%, similar to the prevalence in the general population. Prevalence by diagnosis was: 0.2% for bulimia nervosa (BN), 4.8% for binge eating disorder (BED), and <0.1% for eating disorders not otherwise specified-purging disorder (EDNOS-P). Assessing anorexia nervosa (AN) during pregnancy was not done, because of the difficulty in evaluating the weight criterion due to additional weight from the fetus, placenta, and amniotic fluid.

This study also found that the most common course of illness for BN in pre-pregnancy (six months prior) to during pregnancy (18 weeks gestation) was remission or partial remission (74%, combined estimate). For BED, the most common course of illness from pre-pregnancy to during pregnancy (61%) was continuation of the illness, meaning that BED was persisting during pregnancy. For purging disorder, remission was the most common course of illness from pre- to during pregnancy (79%). Also noteworthy was that some women who did not have eating disorders before pregnancy developed them during pregnancy. This pattern was most common with BED, which developed in 2.1% of women who did not report an eating disorder prior to pregnancy. Remission from eating disorders during pregnancy, as well as onset of eating disorders, had been documented in prior literature, but the rates had been unknown. The findings indicate that pregnancy offers a window for remission from BN and EDNOS-P, but may be a risk period for onset of BED.

The course of eating disorders following childbirth was examined in another MoBa study. The prevalence of remission from AN diagnosed pre-pregnancy was 50% 18 months after childbirth, and 59% at 36 months. For BN, corresponding figures were 39% (18 months) and 59% (36 months), for EDNOS-P 46% and 57%, and for BED 45% and 42%. For many women, eating disorders prior to pregnancy continue in the longer-term, which may pose health risks for the mother and child, and as such, warrants action through screening, referral, and intervention pathways.

In MoBa studies published in 2008 and 2011, our team investigated who was most “at risk” of either good outcomes (i.e., remission) or undesirable outcomes (i.e., continuation or onset of an eating disorder) during pregnancy. Compared to pregnant women in MoBa without eating disorders, those with eating disorders prior to or during pregnancy were more likely to have faced psychosocial adversities. Their anxiety and depression symptoms during pregnancy were higher, their life and relationship satisfaction was lower, and they had a higher lifetime risk of sexual and physical abuse. Remission from BN during pregnancy was associated with lower scores on measures of anxiety and depression, higher life satisfaction, and higher self-esteem. Onset of BED during pregnancy was associated with a large range of psychosocial correlates (15 in total!), which confirmed more negative life events and adverse experiences among those with onset of BED relative to pregnant women who did not experience onset. This knowledge provides us with several potential pivot points with which to improve our screening, prevention, and intervention practices among pregnant women.

In an upcoming blog, pregnancy, obstetric, and birth outcomes among women with eating disorders compared to other women in the general population, will be discussed. The topics include unplanned pregnancies in AN, birth and obstetric outcomes, and sex ratio (ratio of males to females born at birth). Stay tuned…

photo credit: bies via Creative Commons

photo credit: Kit4na via Creative Commons