The impact of diet on the health of pregnant women remains an unresolved clinical issue. The aim of this study was to determine and compare the dietary intake of mothers who gave birth to full-term infants whose sizes were appropriate for gestational age (AGA), preterm birth (PTB) infants, and full-term infants who were small for gestational age (SGA). Of the 103 women who participated, 50 gave birth to AGA infants, 30 gave birth to PTB infants, and 23 gave birth to SGA infants. The composition of each woman’s diet was analyzed using a questionnaire completed 3 days postchildbirth. Findings revealed a number of differences between the groups. The percentage of energy obtained from fat and the calcium and lactose intake was all highest in Group AGA. The largest number of differences in intake of fatty acids (FAs) was observed among short- and medium-chain FAs. Lower levels of C4:0, C6:0, C8:0, C10:0, and C14:0 were observed in the diets of women in Group PTB than in Group AGA. C18:0 intake was also lower in Group PTB than in Group AGA. The reduced short-, medium-, and long-chain FA intake by women in Group PTB also affected the total saturated FA intake, which was lowest in that group. These findings suggest that, even in mothers giving birth to children with only slight deviations from normal birth weight or normal gestational duration, differences in diet can be identified, particularly regarding FA content, which may affect the health of the newborn.