Vitamin K Status of Premature Infants: Implications for Current Recommendations

Abstract

Objective. Newborn infants are vitamin K deficient. Vitamin K status in full-term infants after intramuscular vitamin K supplementation at birth has been described. Similar information in growing premature infants has not been reported. The objective of this study was to assess vitamin K status in premature infants by measuring plasma vitamin K and plasma protein-induced in vitamin K absence (PIVKA II) from birth until 40 weeks' postconceptional age. Methods. Premature infants (≤36 weeks' gestation) were divided at birth into groups by gestational age (group 1, ≤28 weeks; group 2, 29–32 weeks; group 3, 33–36 weeks). Supplemental vitamin K (1 mg intramuscularly) was administered at birth followed by 60 μg/day (weight <1000 g) or 130 μg/day (weight ≥1000 g) via total parenteral nutrition. After hyperalimentation, most received vitamin K–fortified enteral feedings with the remainder receiving unfortified breast milk. Blood was obtained for PIVKA II in cord blood and for PIVKA II and vitamin K at 2 weeks and 6 weeks after birth and at 40 weeks' postconception. Results. Of the 44 infants enrolled, 10 infants in each gestational age group completed the study. The patient characteristics for groups 1, 2, and 3 were as follows: gestational age, 26.3 ± 1.7, 30.3 ± 1.3, and 33.9 ± 1.1 weeks; birth weight, 876 ± 176, 1365 ± 186, and 1906 ± 163 g; and days of hyperalimentation, 28.9 ± 16, 16.8 ± 12, and 4.3 ± 4 days, respectively. At 2 weeks of age, the vitamin K intake and plasma levels were highest in group 1 versus group 3 (intake: 71.2 ± 39.6 vs 13.4 ± 16.3 μg/kg/day; plasma levels: 130.7 ± 125.6 vs 27.2 ± 24.4 ng/mL). By 40 weeks' postconception, the vitamin K intake and plasma levels were similar in all 3 groups (group 1, 2, and 3: intake, 11.4 ± 2.5, 15.4 ± 6.0, and 10.0 ± 7.0 μg/kg/day; plasma level, 5.4 ± 3.8, 5.9 ± 3.9, and 9.3 ± 8.5 ng/mL). None of the postnatal plasma samples had any detectable PIVKA II. Conclusions. Premature infants at 2 weeks of age have high plasma vitamin K levels compared with those at 40 weeks' postconceptional age secondary to the parenteral administration of large amounts of vitamin K. By 40 weeks' postconception, these values are similar to those in term formula-fed infants. Confirming “adequate vitamin K status,” PIVKA II was undetectable by 2 weeks of life in all of the premature infants. With the potential for unforeseen consequences of high vitamin K levels, consideration should be given to reducing the amount of parenteral vitamin K supplementation in the first few weeks of life in premature infants.vitamin K, PIVKA II, premature, total parenteral nutrition, enteral nutrition.