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Newborn infants routinely receive an injection of vitamin K after birth in order to prevent (or slow) a rare problem of bleeding into the brain weeks after birth. Vitamin K promotes blood clotting. The fetus has low levels of vitamin K as well as other factors needed in clotting. The body maintains these levels very precisely.1 Supplementation of vitamin K to the pregnant mother does not change the K status of the fetus, confirming the importance of its specific levels.
Toward the end of gestation, the fetus begins developing some of the other clotting factors, developing two key factors just before term birth.2 It has recently been shown that this tight regulation of vitamin K levels helps control the rate of rapid cell division during fetal development. Apparently, high levels of vitamin K can allow cell division to get out of hand, leading to cancer.
What's the Concern?
The problem of bleeding into the brain occurs mainly from 3 to 7 weeks after birth in just over 5 out of 100,000 births (without vitamin K injections); 90% of those cases are breastfed infants,3 because formulas are supplemented with unnaturally high levels of vitamin K. Forty percent of these infants suffer permanent brain damage or death.
The cause of this bleeding trauma is generally liver disease that has not been detected until the bleeding occurs. Several liver problems can reduce the liver's ability to make blood-clotting factors out of vitamin K; therefore extra K helps this situation. Infants exposed to drugs or alcohol through any means are especially at risk, and those from mothers on anti-epileptic medications are at very high risk and need special attention.
Such complications reduce the effectiveness of vitamin K, and in these cases, a higher level of available K could prevent the tragic intracranial bleeding. This rare bleeding disorder has been found to be highly preventable by a large-dose injection of vitamin K at birth.
The downside of this practice however is an 80% increased risk of developing childhood leukemia. While a few studies have refuted this suggestion, several tightly controlled studies have shown this correlation to be most likely.4,5 Apparently the cell division that continues to be quite rapid after birth continues to depend on precise amounts of vitamin K to proceed at the
proper rate. Introduction of levels that are 20,000 times the newborn level, the amount usually injected, can have devastating consequences.
The Newborn's Diet
Nursing raises the infant's vitamin K levels very gradually after birth so that no disregulation occurs that would encourage leukemia development. Additionally, the clotting system of the healthy newborn is well planned, and healthy breastfed infants do not suffer bleeding complications, even without any supplementation.6
While breastfed infants demonstrate lower blood levels of vitamin K than the "recommended" amount, they show no signs of vitamin K deficiency (leading one to wonder where the "recommended" level for infants came from). But with vitamin K injections at birth, harmful consequences of some rare disorders can be averted.
Infant formulas are supplemented with high levels of vitamin K, generally sufficient to prevent intracranial bleeding in the case of a liver disorder and in some other rare bleeding disorders. Although formula feeding is seen to increase overall childhood cancer rates by 80%, this is likely not related to the added vitamin K.