First let me say that our first child had the vitamin K shot, but our second and third children did not because it did not seem necessary. Perhaps this makes me biased. However, we are firm believers in making sure our food gives us nutrition. So for those who are concerned or curious, here is why we were not interested in the vitamin K shot.
If your baby's cord is clamped after it stops pulsating then your baby gets all the blood he or she needs. This blood will help baby to have vitamin K as well. Plus, there is no need to treat a disease that is not occurring in a newborn. Yes, some babies DO have bleeding issues but it is rare. The symptoms of this disorder, called Vitamin K deficiency bleeding or VKDB, include oozing at the cord stump site, blood in stool, or blood in urine (http://www.lpch.org/DiseaseHealthInfo/HealthLibrary/hrnewborn/hrdn.html). Your child's chance of having this issue is estimated to be, "one in 10,000" (http://www.westernsussexhospitals.nhs.uk/services-and-treatments/maternity/what-happens/after-your-baby-is-born/vitamin-k/vkdb/).
If you are still considering the vitamin K shot then check out the ingredients. I had a tough time finding copies of the package inserts but was able to get the following information. There is benzyl alcohol which can cause"toxicity" in babies. Also, "Hemolysis, jaundice, and hyperbilirubinemia in newborns, particularly in premature infants, may be related to the dose of AquaMEPHYTON". "Hemolysis, jaundice, and hyperbilirubinemia in newborns, particularly in premature infants, may be related to the dose of AquaMEPHYTON" (http://web.archive.org/web/20070213093306/http://www.fda.gov/medwatch/SAFETY/2003/03Feb_PI/AquaMEPHYTON_PI.pdf ). When looking over a package insert notice that the vitamin K is synthetic, not from natural sources, and the dosage is always much higher than the recommended amount of vitamin K a baby should receive in a day (http://onlinehealthnews.org/2009/12/high-risks-to-your-baby-from-vitamin-k-shot-they-dont-warn-you-about/).
There also appear to be risks with the vitamin K shot. These risks are under-reported when they become injuries. However, the shot has been linked to leukemia as children age as well as anaphylaxis and infections at the injection site http://www.whale.to/vaccine/vitamin_k_shot.html. As a parent you need to do some research and find out if the benefits outweigh the risks.
If you choose to do a vitamin K supplement perhaps a better choice than a needle being shoved into your child's thigh, is to have nursing mom be sure to take the oral tablets. Even better, get he vitamin K from food (http://www.whfoods.com/genpage.php?tname=nutrient&dbid=112)!