Maternal administration of vitamin K does not improve the coagulation profile of preterm infants.

The effect of maternal administration of vitamin K1 on cord blood prothrombin time, activated partial thromboplastin time, activity of factors II, VII, and X, and antigen levels of factors II and X in infants less than 35 weeks' gestation was evaluated. Pregnant women in preterm labor were randomly assigned to receive 10 mg of vitamin K1 intramuscularly or no injection. If delivery did not occur in 4 days, the dose of vitamin K1 was repeated. Women who continued their pregnancy 4 days beyond the second dose received 20 mg of vitamin K1 orally daily until the end of the 34th week of gestation. The birth weights of infants ranged from 370 to 2550 g and gestational age ranged from 22 to 34 weeks. The prothrombin time, activated partial thromboplastin time, factors II, VII, and X activity, and factors II and X antigen levels were not statistically different in either group of infants. Intraventricular hemorrhage occurred in 25 of 51 control infants and 25 of 47 vitamin K-treated infants. More control infants had grade III intraventricular hemorrhage on day 1 (P = .032), but on day 3 and 14 of life, the severity of intraventricular hemorrhage was comparable in both groups. Infants in whom an intraventricular hemorrhage developed were significantly smaller, younger, and more critically ill than infants without intraventricular hemorrhage. Administration of vitamin K1 to pregnant women at less than 35 weeks' gestation does not improve the hemostatic defects nor does it reduce the incidence or severity of intraventricular hemorrhage in their infants.