Plasma vitamin K1 in mothers and their newborn babies
Insights
Plasma vitamin K1 (phylloquinone) levels are significantly lower in newborns compared to their mothers, indicating poor placental transfer. This finding suggests a need to re-evaluate vitamin K prophylaxis in the neonatal period.
Area of Science:
- Biochemistry
- Neonatal Medicine
- Pharmacology
Background:
- Plasma vitamin K1 (phylloquinone) is crucial for blood coagulation.
- Physiological hypoprothrombinemia is common in newborns.
- Current vitamin K prophylaxis practices may require reassessment.
Purpose of the Study:
- To quantify plasma vitamin K1 levels in healthy adults, pregnant women at term, and their neonates.
- To investigate the placental transfer of vitamin K1.
- To correlate neonatal vitamin K1 levels with physiological hypoprothrombinemia.
Main Methods:
- High-performance liquid chromatography (HPLC) was used to assay plasma vitamin K1.
- Plasma samples were collected from fasting adults, term pregnant women, and their neonates.
- Maternal vitamin K1 levels were supplemented intravenously before delivery in a subset of participants.
Main Results:
- Mean plasma vitamin K1 in adults was 0.26 ng/ml.
- Maternal plasma K1 at term averaged 0.20 ng/ml, with undetectable levels in most neonates.
- Intravenous maternal vitamin K1 supplementation increased maternal levels significantly but resulted in only minimal transfer to neonates.
Conclusions:
- Vitamin K1 does not readily cross the placenta, or fetal uptake is limited.
- Low neonatal vitamin K1 levels likely explain physiological hypoprothrombinemia.
- Current vitamin K prophylaxis strategies for newborns may need re-evaluation.
Abstract:
Plasma vitamin K1 (phylloquinone) was assayed in normal adults and pregnant women at term and their babies by a method based on high-performance liquid chromatography. The mean plasma concentration in 30 healthy, fasting adults was 0.26 ng/ml (range 0.10-0.66). 8 out of 9 healthy mothers at term had a mean K1 concentration of 0.20 ng/ml (range 0.13-0.29), but K1 was not detected in the cord plasma of their babies. 1 mg vitamin K1 given intravenously to 6 mothers shortly before delivery raised their plasma K1 to 45-93 ng/ml: K1 was then detectable in the cord plasma of 4 of the 6 infants but at a much lower concentration which did not exceed 0.14 ng/ml. The large concentration gradient between maternal and neonatal plasma suggests that vitamin K1 does not cross the placenta readily or that the uptake by fetal plasma is low, perhaps because of low levels of a binding lipoprotein. The low levels of vitamin K in the cord plasma of the normal newborn would explain "physiological" hypoprothrombinaemia and suggest the need to reassess current clinical practice in respect of vitamin K prophylaxis in the early neonatal period.
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