The authors confirm the absence of a marked variation in levels of gamma-glutamyl-transpeptidase in women under the influence of oestrogens, but a considerable rise in this enzyme in the newborn, particularly after delivery following vaginal obstetrical manoeuvre. They base these findings on 242 samples taken from pregnant women in the 3 trimesters of normal pregnancies and after delivery, and in the cord blood of newborn infants as well as in patients taking oral contraception. There is a slight rise in the levels of immunoglobulins A in the 3rd trimester of pregnancy. The overall rise in the blood levels of transferrin under the effect of oestrogens is confirmed. Norms were obtained for the levels of the IgA/T ratio which drops progressively as pregnancy progresses and with oral contraception. It has been found that in the last two trimesters the upper limit of the normal is 1 for the IgA/T ratio as compared with 1.9 in the general population. The study of these constants is of value when screening for maternal alcoholism and as a consequence for the prevention of the fetal alcohol syndrome.