The purpose of the study — retrospective analysis of the course of gestation and childbirth in patients with a low body weight, followed by the identification of those risk factors which effect the condition of the fetus and the newborn. Material and methods. Comparative analysis of pregnancy and childbirth in 567 women with a low body weight, and 1080 women with initially normal body weight, was carried out. Results. The percentage of pregnant women with low body weight in the total population of pregnant women is 25.34%. In 90.3% of these patients, the main cause of low body weight was an incorrect lifestyle, which included a combination of several factors: malnutrition (including dieting aimed at reducing body weight), stress, excessive physical activity and lack of sleep. The combination of low body weight and insufficient weight gain during pregnancy has a statistically significant impact on the increase in the frequency of iron deficiency anemia (65.42%), hypotension (25.23%), hypoxia (29.91%), placental insufficiency (68.22%), and fetal growth retardation syndrome (44.86%). In cases of excessive body weight gain in pregnant women, even in the presence of the initial body weight deficiency, the frequency of arterial hypertension associated with pregnancy increases significantly (15.79%). The frequency of caesarean section in pregnant women with low body weight is 33.33%, which is significantly higher than in the population as a whole (p<0.001). The main indication for caesarean section in pregnant women with low body weight is fetal distress (32.81%). Conclusion. Weight loss in women leads to a maladaptation of the mother’s body during pregnancy, which is an objective factor in the formation of fetal distress.