Background and Objectives: An increased prevalence of low maternal weight and insufficient pregnancy weight gain may be responsible for an increase in low birthweight infants in Japan. We aimed to examine the ef- fects of individualised dietary education at medical check-ups on maternal/fetal outcomes in Japanese women. Methods and Study Design: Four hundred and six underweight and normal weight singleton pregnant women, who attended check-ups at an obstetric facility until ≥30 weeks gestation and delivered at 36-41 weeks gestation, were selected for analyses. Weight gain was assessed at each check-up based on the official “Dietary Guidelines for Pregnant and Lactating Women”. Individual dietary advice was provided by dieticians to those with insuffi- cient or excess weight gain status around 28 weeks gestation. The medical records from uncomplicated singleton deliveries (36-41 weeks gestation) at the same facility from 2008-2010 were used (n=792) to examine the effect of dietary education on maternal/fetal outcomes. Results: Pre-pregnancy underweight was present in >24% of women in both the intervention and non-intervention groups. Adequate weight gain occurred more frequently in the intervention group (p<0.01). There were no significant differences in mean birthweight or the proportion of low birthweight infants. However, the proportion of extremely small for gestational age infants (birthweight <3rd percentile) was lower in the intervention group (p=0.011). There were no differences in the frequency of caesare- an delivery, pregnancy induced hypertension, or infant Apgar scores <7. Conclusions: Dietary education during pregnancy check-ups promotes adequate maternal weight gain and helps prevent extreme fetal growth restraint.