Current research on pregnancy outcomes in women with anorexia nervosa has yielded conflicting results. While some studies report an increased risk of cesarean delivery, miscarriage, preterm birth, and small-for-gestational age births in this population, others find no association. Many of the studies are limited by small sample size and do not account for severity of illness.
In a recent study, researchers performed a retrospective cohort study including 2,134,945 pregnancies in Quebec, Canada (1989-2016) using an administrative database that contains discharge summaries from all inpatient hospitalizations. Pregnancy outcomes were assessed in women with anorexia nervosa who required hospital-based treatment before or during pregnancy.
The analysis included 1,910 births (0.1% of the total number) to women who were hospitalized for anorexia nervosa. Women with no hospitalization for anorexia nervosa were used as a comparison group. In adjusted models, anorexia nervosa did not affect risk for preeclampsia, placenta previa, cesarean delivery, or other complications of labor and delivery. Women with anorexia nervosa had a lower risk of postpartum hemorrhage (RR 0.76, 95% CI 0.62–0.93) and gestational diabetes (RR 0.57, 95% CI 0.44–0.73).
However, compared to women who had no history of hospitalization, women with anorexia nervosa hospitalization were nearly twice as likely to have a stillbirth (risk ratio or RR=1.99; 95% CI 1.20-3.30), 1.32 times as likely to experience preterm birth (95% CI 1.13-1.55), 1.69 times a likely to have a low birth weight infant (95% CI 1.44-1.99), and 1.52 times as likely to have a small-for-gestational age birth (95% CI 1.35-1.72). Women with more recent hospitalizations for anorexia nervosa were at greatest risk of adverse infant outcomes. Risk for low birth weight and small-for-gestational age birth were the highest in women hospitalized for anorexia nervosa during pregnancy or within 2 years of delivery.
One of the strengths of this study is its size; with over 1000 women with anorexia, it is one of the largest studies to date. However, one of its limitations is that the current study assesses outcomes only in women with the most severe illness, those women who were hospitalized for anorexia nervosa. In contrast, the Generation R study, which was a population-based study including women with a broader range of eating disorder severity, showed only an increase in adverse outcomes in women with active anorexia who were hospitalized during pregnancy.
In terms of understanding the adverse outcomes we see in women with anorexia nervosa, it is believed that most of the relationship between anorexia nervosa and birth complications is related to poor fetal growth. Women with low calorie and protein intake have lower body mass index, which is a risk factor for preterm birth, low birth weight, and small-for-gestational age infants. Previous studies have demonstrated that low pre-pregnancy body mass is associated with decreased uteroplacental blood flow and a diminished transfer of nutrients to the growing fetus. Anorexia nervosa is also associated with iron, folate, zinc, and vitamin A deficiencies, factors with may also contribute to worse outcomes.
This study clearly shows that having active illness during pregnancy (as indicated by hospitalization during pregnancy) is associated with worse outcomes. It is interesting to note that women who had an active eating disorder during the two years prior to conception also carried an increased risk. Presumably these women were well enough to conceive and to carry a pregnancy beyond the 20th week, yet they may not have been fully “recovered”. Whether this reflects persistent unhealthy eating behaviors, residual hormonal abnormalities, or alterations in metabolism and nutritional status, we do not know. However, this is an important piece of information to keep in mind when counseling women with anorexia nervosa regarding their plans for pregnancy.
Ruta Nonacs, MD PhD
Ante Z, Luu TM, Healy-Profitós J, He S, Taddeo D, Lo E, Auger N. Pregnancy outcomes in women with anorexia nervosa. Int J Eat Disord. 2020 May;53(5):403-412.
Charbonneau KD, Seabrook JA. Adverse Birth Outcomes Associated with Types of Eating Disorders: A Review. Can J Diet Pract Res. 2019 Sep 1;80(3):131-136.