The investigation of many hemostatic defects in the newborn is limited by the lack of normal reference values. This study was designed to determine the postnatal development of the human coagulation system in the healthy full-term infant. Consecutive mothers of healthy full-term infants born at St JosePh′s Hospital in the city of Hamilton were approached for consent. One hundred eighteen full-term infants (37 to 42 week's gestational age) were entered into the study. Demographic information and a 2-mL blood sample were obtained in the postnatal period on days 1, 5, 30, 90, and 180. Between 40 and 79 full-term infants were studied on each day for each of the coagulation tests. Plasma was fractionated and stored at -70 degrees C for batch assaying of the following tests: prothrombin time, activated partial thromboplastin time, thrombin clotting time, and factor assays (biologic): fibrinogen, II, V, VII, VIII, IX, X, XI, XII, and high- molecular weight kininogen. Factor XIII subunits A and S, von Willebrand factor, and the inhibitors antithrombin III, alpha 2- antiplasmin, alpha 2-macroglobulin, alpha 1-antitrypsin, C1 esterase inhibitor, protein C, and protein S were measured immunologically. Plasminogen, prekallikrein, and heparin cofactor II were measured by using chromogenic substrates. The large number of infants studied at each time point allowed us to determine the following: the range of normal for each test at five time points in the postnatal period; that coagulation tests vary with the postnatal age of the infant; that different coagulation factors show different postnatal patterns of maturation; and that near-adult values are achieved for most components by 6 months of life. In summary, this large cohort of infants studied consecutively in the postnatal period allowed us to determine the normal development of the human coagulation system in the full-term infant.

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This study was designed to determine the postnatal development of the human coagulation system in the healthy premature infant. Consecutive mothers of healthy premature infants born at either St Joseph's Hospital or McMaster University Medical Centre in Hamilton were asked for consent. One hundred thirty-seven premature infants (30 to 36 weeks of gestational age) entered the study. The premature infants did not have any major health problems and did not require ventilation or supplemental oxygen. Demographic information and a 20-mL blood sample were obtained in the postnatal period on days 1, 5, 30, 90, and 180. Between 40 and 96 premature infants were studied on each day for each of the following tests: prothrombin time, activated partial thromboplastin time, thrombin clotting time, plasminogen; 13 factor assays [fibrinogen, II, V, VII, VIII, IX, X, XI, XII, XIII, high-mol-wt kininogen (HMWK), prekallikrein (PK), von Willebrand factor (vWF)] and eight inhibitors [antithrombin III (AT-III), heparin cofactor II, alpha 2-antiplasmin, alpha 2-macroglobulin, alpha 1-antitrypsin, C1 esterase inhibitor, protein C (PC), and protein S (PS)]. A combination of biologic and immunologic assays were used. Between 30 to 36 weeks there was a minimal effect of gestational age for levels of AT-III, PC, and factors II and X only; therefore, the entire data set was used to generate reference ranges for these components of the coagulation system for premature infants. Next, the results for the premature infants were compared with those of a previously published study in 118 fullterm infants and with those for adults. An effect of gestational age was shown for plasminogen, fibrinogen, factors II, V, VIII, IX, XI, XII, HMWK, and all eight inhibitors. In general, the postnatal maturation towards adult levels was accelerated in premature infants as compared with the fullterm infants. By 6 months of age, most components of the coagulation system in premature infants had achieved near adult values.

A cohort study was performed to determine the postnatal development of the coagulation system in the “healthy” premature infant. Mothers were approached for consent and a total of 132 premature infants were entered into the study. The group consisted of 64 infants with gestational ages of 34-36 weeks (prem 1) and 68 infants whose gestational age was 33 weeks or less (prem 2). Demographic information and a 2 ml blood sample were obtained on days 1, 5, 30, 90, and 180. Plasma was fractionated and stored at −70°C for batch assaying of the following tests: screening tests, PT, APTT; factor assays (biologic (B)); fibrinogen, II, V, VII, VIII:C, IX, X, XI, XII, prekallikrein, high molecular weight kininogen, XIII (immunologic (I)); inhibitors (I), antithrombin III, aα2-antiplasmin, α2-macroglobulin, α-anti-trypsin, Cl esterase inhibitor, protein C, protein S, and the fibrinolytic system (B); plasminogen. We have previously reported an identical study for 118 full term infants. The large number of premature and full term infants studied at varying time points allowed us to determine the following: 1) coagulation tests vary with the gestational age and postnatal age of the infant; 2) each factor has a unique postnatal pattern of maturation; 3) near adult values are achieved by 6 months of age; 4) premature infants have a more rapid postnatal development of the coagulation system compared to the full term infant; and 5) the range of reference values for two age groups of premature infants has been established for each of the assays. These reference values will provide a basis for future investigation of specific hemorrhagic and thrombotic problems in the newborn infant.