Eating disorders are common psychiatric disorders among women of reproductive age, and the prevalence of eating disorders has been increasing over time in Japan and other countries. The aim of the present study was to assess perinatal outcomes in maternal anorexia nervosa in Japan and to explore methods to improve perinatal outcomes. This study consists of a case series describing 13 single pregnancies of 11 women with a history of anorexia nervosa, and a cross-sectional study comparing 13 cases with 240 healthy controls. In the case group, nine cases conceived while underweight, including three who had fertility treatment. Anorexia symptoms during pregnancy were quite common, and pregnant smokers presented with extremely disturbed eating behaviors. In a cross-sectional study, premature birth and the standard deviations from the mean birth weight and mean head circumference at birth were evaluated as outcome measures. The adjusted odds ratios or the adjusted differences between two means for the above outcomes were estimated by two approaches: multivariate models and matching analysis. Statistical analysis showed that maternal anorexia nervosa was associated with an increased risk of premature birth and symmetric growth restriction mediated by low pre-pregnancy body mass index and poor gestational weight gain which were adjusted as confounders. Smoking during pregnancy was a potential indicator of abnormal eating behavior and could be predictive of poor perinatal outcomes. We therefore conclude that remission of anorexia nervosa before pregnancy could improve perinatal outcomes through both normal nutrition and smoking cessation. Fertility treatment while underweight is not recommended.