The aim of this work is to evaluate, by means of an alternative method, the fetal lung maturation by means of measurement of the electrical conductivity of the amniotic fluid correlated with the phospholipid content. In vitro measurements were made in some 100 amniotic fluid samples at different gestational stages. A considerable change was observed in the electrical conductivity of the amniotic fluid in the last period of pregnancy, which reflects the increase in phospholipid concentration, when lung maturation is reached. We hope that further investigations, on wider case histories, will enable the application in vivo of the above-mentioned methodology.