Anorexia and Pregnancy

It's natural to wonder about the effects of anorexia on pregnancy. Given that weight gain is a huge fear for a person with anorexia and that pregnancy requires weight gain, one might assume that anorexia would make pregnancy particularly dangerous. Prior research, though, didn't necessarily bear this out. I learned more at the 2008 International Conference on Eating Disorders (ICED).

University of North Carolina Chapel Hill researcher Cynthia Bulik, PhD, presented a study on the effects of anorexia and other eating disorders on pregnancy and childbirth. The study used data from the Norwegian Mother and Child Cohort Study, which has a distinct advantage over other data sets because it allowed researchers access to data from nearly 36,000 new mothers in Norway (from every geographical part of the country).

Dr. Bulik and colleagues hypothesized that anorexia might be associated with a greater chance of preterm birth, low birth weight, small size for the baby's gestational age at birth (SGA) and lower gestational weight gain in the mother. They gathered data at three points: week 17 of pregnancy (standard time for an ultrasound in Norway), birth and six months after birth.

Measuring Anorexia's Effects on Pregnancy and Childbirth

Of the mothers studied, just 35 met the basic criteria for anorexia nervosa, and the results were striking:

• Preterm birth: Though the difference was not statistically significant, those with anorexia were actually less likely to have a preterm birth than others in the population.
• Birth weight: There was no measured correlation between maternal anorexia and babies' birth weight, which was similar to babies of mothers without eating disorders.
• Size for gestational age: Babies seemed to have appropriate weight for their time of birth.
• Gestational weight gain: On a reassuring note, those with anorexia gained an average of 18 kg (39.6 pounds), which was significantly more than the 15 kg (33 pounds) gained by those who ate normally.
  

  Essentially, those with anorexia seemed to respond to the need to gain weight to support their babies, contradicting the study's hypothesis.

Significant Links Between Anorexia and Pregnancy

So if those with anorexia seem to have normal pregnancies and births with respect to babies' weight and maternal weight, is anything affected by the eating disorder? Some associations did show up:

• Maternal age: Those with anorexia became mothers at an average age of 27, three years earlier than those without an eating disorder.
• Body Mass Index: As might be expected, mothers with a history of anorexia had very low BMI, an average of 18; those without eating disorders averaged 24. This makes the mothers' ability to gain weight even more remarkable.
• Smoking: 37% of those with anorexia smoked during pregnancy as compared to just 9.2% of those with no eating disorder, which was particularly disturbing. Why this trend exists is yet to be explained.
• Likelihood of epidural: The group with a history of anorexia were 70 to 80% more likely to have an epidural administered during birth. Exactly what anorexia might do to contribute to this is unclear. Perhaps anorexia lowers the body's endurance, making birth more difficult. It also may be that those with anorexia are simply more attuned to pain.

What the Data Says About Anorexia and Pregnancy

The hopeful news is that mothers with anorexia seemed able to gain weight normally in support of their babies, and that babies seemed to gain appropriate weight as well. Dr. Bulik suggested that this phenomenon may help to counter any negative effects that pre-pregnancy anorexia in mothers has on their babies.

Though there was a measurable trend that mothers with anorexia were more likely to make slow labor progress than others, the effect was small enough that it may have occurred by chance.

The study had some other notable limitations:

• Participants were more likely to be educated than the general Norwegian population.
• While more than 36,000 Mothers in the available data participated, this was only 42% of the total (nearly 100,000).
• No data existed to describe the severity of eating disorders reported. It's not clear if this population had a normal distribution of eating disorders or if these mothers' symptoms tended to be more severe or less severe.

While this portion of the study did not produce expected results, it is common for research like this to have a profound impact. It may be that our thinking in this area must change significantly -- either to modify our assumptions of anorexia's impact on pregnancy or to drive us toward even more powerful study methods that can bridge gaps in our knowledge.