Maternal food intakes were assessed by 7-d weighed diet records during the three trimesters of pregnancy in 75 mothers in a low socio-economic groups. Mean (+/- s.e.) energy intakes in the first, second and third trimesters were 1613 +/- 45.7, 1723 +/- 45.4, 1772 +/- 50.2 kcal respectively. Mean (+/- s.e.) energy intakes of nine mothers with babies less than 2500 g at birth were 1446 +/- 95.1 kcal, compared with 1723 +/- 39.9, P less than 0.001. Intake of almost all nutrients was lower in mothers of babies less than 2500 g, but only the difference in fat (62.1 +/- 5.0 vs 72.6 +/- 1.75, P less than 0.025) and pyridoxine (0.92 +/- 0.06 vs 1.47 +/- 0.14, P less than 0.005) intakes reached statistical significance.