BACKGROUND: There exists very little information on possible effects on birth size of micronutrient intakes at levels that are usually encountered among pregnant women in developed countries. AIM OF THE STUDY: To examine the relation of the intake of 20 micronutrients with birth weight, placental weight, birth length and head circumference of the offspring. METHODS: In a cohort of 222 Caucasian women with singleton pregnancies in Boston, USA, diet during pregnancy was ascertained at the 27th gestational week through a validated semi-quantitative food frequency questionnaire, covering also intake of dietary supplements. Micronutrient intakes were correlated with birth size parameters after adjustment for confounding variables, including total energy intake. RESULTS: Pantothenic acid, sodium and vitamin E were positively associated with all four birth size parameters. For pantothenic acid the association was statistically significant with respect to birth length, whereas for sodium with respect to head circumference and for vitamin E with respect to birth weight. In contrast, zinc was inversely associated with all four birth size parameters and the association was statistically significant with respect to head circumference. CONCLUSIONS: In a moderately sized prospective study, we found evidence that pregnancy intake of pantothenic acid, vitamin E and sodium may be positively related with at least one of the studied birth size parameters, whereas an inverse association was found with respect to zinc intake. For the remaining 16 micronutrients, our findings indicate that they are not associated with birth size, at least within the range of intake encountered in this investigation. The results of this exploratory analysis need to be confirmed before pathophysiologic interpretations and generalizations are attempted.