The Unintended Consequences of Giving Acetaminophen to Newborns

A study assessing the effectiveness of acetaminophen for neonatal pain relief found that use of acetaminophen shortly after birth may aggravate a subsequent stress response.¹ The Swiss researchers who conducted the study also found that the use of a pain reliever after birth probably is unnecessary, because the pain scores of infants born by assisted vaginal delivery are low in the period immediately after birth.
   
In a double-blind, placebo-controlled trial, 123 term and near-term infants who were delivered by forceps or vacuum were randomized to receive suppositories of either acetaminophen or placebo at 2 and 8 hours after birth. The dose of acetaminophen, either 60 mg, 80 mg, or 100 mg, was based on birth weight (less than 3000 g, 3000 to 4000 g, greater than 4000 g, respectively). The researchers used the Echelle de Douleur et d’Inconfort du Nouveau-Ne (EDIN, translated as Neonatal Pain and Discomfort Scale) to assess pain and discomfort during the first 24 hours of life. In addition, the Bernese Pain Scale for Neonates (BPSN) was used to determine response to a heel prick for metabolic screening at 2 to 3 days after birth.
   
The EDIN scale uses the indicators of facial activity, body movements, quality of sleep, quality of contact with nurses, and consolability to assess for prolonged pain.² The BPSN is based on the following behavioral and physiological indicators: facial expression, body posture, movements, vigilance, heart rate, respiratory rate, blood pressure, and oxygen saturation.²
   
Employing the EDIN scale, the researchers found that pain scale ratings were low at birth and declined within 4 hours of life for both study groups (P < 0.01).1 When BPSN scores were used to assess pain after a heel stick at 2 to 3 days of life, the scores among the infants who received acetaminophen were significantly higher than the scores among those who received placebo (median scores, 4 vs 2, respectively), although both BPSN scores are considered low. This difference was significant when BPSN was scored by nurses at bedside (P = 0.017) and when scored off-site from videos (P = 0.04). Of the 62 infants who received acetaminophen, 35 (57%) cried after the heel stick, compared with 25 (41%) of 61 infants who were given placebo (P = 0.086).
   
These findings indicate that giving newborn infants acetaminophen shortly after birth may aggravate a subsequent pain response, a significant downside to a practice meant to minimize discomfort in newborns.

Pertinent Points:
- Use of acetaminophen in newborns 2 to 8 hours after birth was associated with an aggravated pain response 2 to 3 days later.
- The effects of acetaminophen and other pain relievers on perinatal neural plasticity require further investigation.