The influence of heavy lifting during pregnancy on gestational age, birthweight and the risk of fetal death (spontaneous abortion or stillbirth) was investigated in a prospective study of 3906 occupationally active women. Information on exposure was collected at the women's first contact with the antenatal care centres in Orebro County from October 1980 to June 1983. Logistic and linear regression were used to analyse the data, allowing for several non-occupational factors in the models. Women who reported heavy lifting did not have in general more unfavourable outcomes than other women, although the risk estimates varied between different occupational categories. Lifting of weights greater than or equal to 12 kg more than 50 times per week increased the risk of pre-term birth (less than 37 weeks of gestation--odds ratio 1.7), but only among women who stopped working before the 32nd week of pregnancy. Unfavourable outcomes were more common among those who reported chemical exposure during pregnancy. The preventive routines and regulations in Sweden may have helped to reduce possible risks from heavy lifting during pregnancy.