Vitamin K status of premature infants: Implications for current recommendations

Objective. Newborn infants are vitamin K deficient. Vitamin K status in ful l-term infants after intramuscular vitamin K supplementation at birth has b een described. Similar information in growing premature infants has not bee n reported. The objective of this study was to assess vitamin K status in p remature infants by measuring plasma vitamin K and plasma protein-induced i n vitamin K absence (PIVKA II) from birth until 40 weeks' postconceptional age. Methods. Premature infants (less than or equal to 36 weeks' gestation) were divided at birth into groups by gestational age (group 1, less than or equ al to 28 weeks; group 2, 29-32 weeks; group 3, 33-36 weeks). Supplemental v itamin K (1 mg intramuscularly) was administered at birth followed by 60 mu g/day (weight <1000 g) or 130 <mu>g/day (weight greater than or equal to 10 00 g) via total parenteral nutrition. After hyperalimentation, most receive d vitamin K-fortified enteral feedings with the remainder receiving unforti fied breast milk. Blood was obtained for PIVKA II in cord blood and for PIV KA II and vitamin K at 2 weeks and 6 weeks after birth and at 40 weeks' pos tconception. Results. Of the 44 infants enrolled, 10 infants in each gestational age gro up 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, r espectively. 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 mug/kg/day; plasma levels: 130.7 +/- 125.6 vs 27.2 +/- 24.4 ng/mL). By 40 w eeks' postconception, the vitamin K intake and plasma levels were similar i n all 3 groups (group 1, 2, and 3: intake, 11.4 +/- 2.5, 15.4 +/- 6.0, and 10.0 +/- 7.0 mug/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' p ostconception, these values are similar to those in term formula-fed infant s. Confirming "adequate vitamin K status," PIVKA II was undetectable by 2 w eeks of life in all of the premature infants. With the potential for unfore seen consequences of high vitamin K levels, consideration should be given t o reducing the amount of parenteral vitamin K supplementation in the first few weeks of life in premature infants.