Vitamin K is given to newborns to prevent vitamin K deficiency bleeding (VKDP), which used to be called hemorrhagic disease of the newborn.
There's three types of VKDP: 1) early onset, which occurs 24 hours after birth or less; it's very rare and is usually due to meds the mother has taken that promote bleeding (e.g., anticoagulants); 2) classic onset, which occurs 2-7 days after birth; and 3) last onset, which is any VKDB that happens more than 2 weeks after birth.
Aside from some maternal medications, some other risk factors include neonatal CF, hepatitis, diarrhea, prematurity, a complicated delivery (e.g., forceps-assisted), and breastfeeding (formula contains higher levels of vitamin K;
one article from the nursery at Stanford's School of Medicine states that breast milk contains 1 – 9 micrograms per liter versus formula's 53-66 micrograms per liter and I've seen similar numbers elsewhere).
But VKDB, although very rare, can occur in babies who do not have any of the risk factors, which is why it is recommended for all babies.
From Women's Health Information of the UK:
Vitamin K for newborns...Unfortunately, in about 1/3 of cases, the vitamin K deficiency bleed occurs without prior warning or risk factor. It has been estimated that if vitamin K were only given to high risk babies, among the 800,000 or so annual births in the UK, there might be:
* 60 to 80 babies who suffer a bleed
* 15 to 20 babies suffering a bleed into the brain
* 4 to 6 babies who die from the bleed into the brain
* 10 to 20 babies who may be brain damaged because of the bleeding...
So the rate in that study of bleeding without supplemental vitamin K is 0.0075-0.01%.
...
Good data on the incidence rate of VKDB are hard to find. An
eMedicine article on vitamin K deficiency states that the classic form occurs in 0.25-1.7% of newborns and the late onset form in 20 live births per 100,000 among infants who did not receive supplementation.
The oral form is usually recommeneded only if a person refuses the injection. The one problem is that there have not been big studies on its effectiveness for early or late onset VKDB, and there's some concern that even multiple doses of the oral form is not as effective in preventing late onset VKDB. (There's an AAP publication that talks about this and other issues:
Controversy Concerning Vitamin K and the Newborn). Other possible issues is the lower absorption of the oral versus IM, the need for multiple doses, and problems with kids spitting up or refusing to swallow the oral dose.
There is also controversy over the optimum oral dosing regime, in part because of concerns that oral vitamin K is not fully effective against late onset VKDB. During the scare concerning the injectable vitamin K (mentioned below), the British Medical Journal published a review of vitamin K administration in the UK at that time. It noted that "
No consensus exists regarding the dose or frequency of administration of oral vitamin K, the total dose varying by a factor of 65. The commonest regimens recommend three doses of 0.5-1.0 mg over the first six weeks, but 37 neonatal units (15% of births) did not recommend any doses beyond 7 days of age, despite reports of late failure of single oral dose prophylaxis."
Neonatal vitamin K prophylaxis in the British Isles: current practice and trends, BMJ, 1995;310:632-633 (11 March)
The vitamin K analogue given to newborns is phytonadione. The major adverse effect is anaphaxis. This can occur with the oral dose as well as the injection; I don't know if anaphylaxis is more prevalent with one dosing form or another.
One concern that arose several years ago was a possible link between vitamin K injections and pediatric leukemia. Recent studies have not found a connection.
From the journal Pediatrics (Vol. 108 No. 5 November 2001, pp. 1117-1122):
Vitamin K Status of Premature Infants: Implications for Current Recommendations
...In 1992, Golding et al31 questioned the safety of prophylactic intramuscular vitamin K at birth and reported an associated increased rate of childhood cancer. This study had several limitations. Several large population studies refute these findings.32-40 Limited basic science data implicating vitamin K in causing increased sister chromatid exchanges in human and animal lymphocytes is contradictory. Both the American and the Canadian pediatric societies have reaffirmed their confidence in intramuscular vitamin K prophylaxis....
From Merck:
Phytonadione - Drug Information Provided by Lexi-Comp...Newborns: Use caution in newborns, especially premature infants; hemolysis, jaundice, and hyperbilirubinemia have been reported with larger than recommended doses. Some dosage forms contain benzyl alcohol which has been associated with "gasping syndrome" in premature infants....
From the National Guidelines Clearinghouse:
Controversies concerning vitamin K and the newborn...Because parenteral vitamin K has been shown to prevent vitamin K deficiency bleeding (VKDB) of the newborn and young infant and the risks of cancer have been unproven, the American Academy of Pediatrics recommends the following:
1. Vitamin K1 should be given to all newborns as a single, intramuscular dose of 0.5 to 1 mg (American Academy of Pediatrics, American College of Obstetricians and Gynecologists, 1992).
2. Additional research should be conducted on the efficacy, safety, and bioavailability of oral formulations and optimal dosing regimens of vitamin K to prevent late vitamin K deficiency bleeding.
3. Health care professionals should promote awareness among families of the risks of late vitamin K deficiency bleeding associated with inadequate vitamin K prophylaxis from current oral dosage regimens, particularly for newborns who are breastfed exclusively....
POTENTIAL HARMS
Some earlier studies attempted to show an association between intramuscular vitamin K administration and increased incidence of childhood cancer, but more recent studies failed to substantiate this concern....
...
From the Linus Pauling Institute:
Vitamin K...[T]wo large retrospective studies in the U.S. and Sweden that reviewed the medical records of 54,000 and 1.3 million children, respectively, found no evidence of a relationship between childhood cancers and vitamin K injections at birth (13, 14). Moreover, a pooled analysis of 6 case-control studies including 2,431 children diagnosed with childhood cancer and 6,338 cancer-free children found no evidence that vitamin K injections for newborns increased the risk of childhood leukemia (15). In a policy statement, the American Academy of Pediatrics recommended that routine vitamin K prophylaxis for newborns be continued because VKDB is life threatening and the risks of cancer are unproven and unlikely....
