Background. The study wants to find out the characteristics of pregnancies, deliveries and newborns with low birth weight (LBW) compared to the newborns with birth weight of 2500 g and more, in respect with the specific situation of the twins. Methods and Results. The records from antenatal clinics and maternity hospitals about 5500 children born within strictly given time limit of 16 months during the years 1991-1992 to mothers with permanent habitation in Brno were evaluated. Children and their families are participating on still running prospective longitudinal study ELSPAC aimed to finding the determinants of the healthy development. The low births weight occurred in 5.42 % of children. There were altogether 48 pairs of twins, the low birth weight occurred in 52.6 % of them. Compared to mothers who delivered the children with birth weight of 2500 g and more, the mothers of children with low birth weight entered the prenatal care later, with less consultations, had more complications both during their pregnancies and the deliveries and their children showed more often kinds of neonatal morbidity. Mothers of the twins were cooperating with antenatal clinics better than other mothers of children with low birth weight. On the other hand, they were suffering from anaemia and hypertension more often than mothers of single children. Comparison of the somatic and functional signs has shown that the twins were less handicapped than the whole set of newborns with low birth weight. The twins with low birth weight formed 16.7 % of the set. Conclusions. The study of the Brno newborn population shows the quantitative differences in the risks, which have influenced the courses and the results of the pregnancies ending by deliveries of children with low birth weight. Results are compared to those whith deliveries of children the birth weight of 2500 g and more.

        Key words: low birth weight, risky factors, twins, single children, anthropology of the mothers, somatic state of newborns, neonatal morbidity, pregnancy and delivery complications, epidemiologic study.