Antithrombin III in fetuses and newborn children

Antithrombin III (AT III) was measured in plasma of healthy fetuses between 20-29 weeks of gestation, in plasma of suspected growth retarded or malformed fetuses between 30-39 weeks of gestation, in healthy newborn infants after delivery, and in healthy infants during the first year of life. Measurements were performed with an AT III assay (Orion Diagnostica, Espoo, Finland Turbox) on nephalometer Turbox. The results were expressed as a percentage of the mean adult value (300 mg/l) and statistically analysed with the non-parametric Kruskal-Walles test. AT III levels in fetuses were low but increasing. They continued to increase after birth (F = 34.53 p < 0.001) and reached adult values in the age between the tenth and twelfth month of life.