You are probably referring to the Vitamin K injection to prevent Neonatal Hemorrhagic Disease. Other injections may be necessary at birth depending on various factors, but Vitamin K is usually given as newborns have a very low supply of the vitamin, which puts them at a high risk of serious bleeding (hemorrhage) which could endanger their health. The injection is given intramuscularly as it is more comfortable for the baby than most other types of injection and oral administration is much less effective for absorbing Vitamin K. Pain and complications are very rare when the injection is administered by a competent nursing staff. While it is always possible to refuse the injection, this is not without risk and most serious bleeding can be prevented with this injection. It is essential to have a discussion with the doctor before birth to make an informed decision and to detect any problems should you decide to refuse the injection anyway.