The main advantage is that these medications do reduce one's perception of pain, as well as the anxiety that is associated with severe pain. This property is most effective in early labor when pain may be getting difficult to cope with, but is not yet as severe as it will become in the later part of labor. Most practitioners feel it is usually safe for baby when narcotics are given to the laboring mother.
Disadvantages of intravenous opioids are that:
With increasing severity of pain, higher doses are required for reduction of pain perception. However, these higher doses are accompanied by the dulling of all senses, leading to altered consciousness, and a reduced urge to breathe. In worst cases these drugs can dangerously impair breathing in the mother and, more commonly, in her newborn.
The chance of seeing side effects in the newborn depend on the dose and time the medication was given prior to delivery. Therefore, these medications are not usually given when delivery is imminent.