A disproportionately large placenta may represent an adaptive response to adverse intrauterine conditions. Both maternal nutritional intake and presence of gestational diabetes (GDM) have been found to affect relative placental growth. As dietary modification is part of the standard management in GDM women, the observed increase in placental size in these women may be partly due to dietary modification. In this study, we set out to examine the relationship between dietary intake and placental size in GDM pregnancies. Food diaries for five consecutive days for 52 women diagnosed with GDM were obtained to assess their nutritional intake in terms of total calories, carbohydrate, protein and fat. Spearman's correlations were calculated for nutritional intake and various factors that may correlate with placental weight. There was a significant inverse relationship (P=0.021) between placental weight and protein intake. No correlations with the other two nutritional components could be demonstrated. Maternal nutritional intake was not correlated with infant birthweight. It is possible that dietary modulations improve GDM pregnancy outcome, not only by improving glycaemic controls but also by affecting placental growth by altering the proportion of protein intake.