The occupational activity of women has become a common phenomenon in the majority of developed countries, where approximately 50% of women at reproductive age are occupationally active. This phenomenon has also been observed in Poland. In the occupational environment many factors may exert an unfavourable effect on the health of the mother and developing foetus. These factors are: passive smoking at the workplace, heavy physical work, working for over 42 hours a week, as well as exposure to various types of chemical substances, electromagnetic waves or radioactive radiation. These factors may considerably increase the risk of occurrence of premature birth or delivery of a baby with reduced birth weight in relation to the gestational age, and may also cause abnormal foetal development. The objective of the study was determination of the effect of occupational activity in pregnancy on the wellbeing of the newborn. The study was carried out from 15 January 2011 – 20 March 2011, at the John Paul II Regional Hospital in Zamość, Poland, using a diagnostic survey. The survey covered 100 mothers who had been occupationally active in pregnancy. The technique applied was a questionnaire form based on the 5‑point Liket scale, which consisted of 39 items. Apart from socio‑demographic data, the questions covered obstetric‑gynaecological history, state of health, life style, course of the last pregnancy, and working conditions. The results confirmed that prolonging the weekly working time by more than 42 hours is conducive for the occurrence of low birth weight of babies, also, passive nicotinism at the workplace may negatively affect newborns’ birth weight. The presence of more than one harmful factor at the workplace results in a slight shortening of pregnancy duration. The scope of problems concerning hazards at the workplace during pregnancy requires further studies on large groups of mothers.