Risk factors for a low 5-minute Apgar score
Supplementary table 2 describes risk factors for a low 5-minute Apgar score <7 and <4. Many perinatal characteristics showed a significant association with low Apgar scores. The intermediate risk factors for an Apgar score <7 with a high crude OR and PAR were: emergency caesarean section (OR 4.84, 95% CI 4.63-5.05), delivery in secondary care (OR 4.25, 95% CI 4.01- 4.47), instrumental vaginal delivery (OR 3.49, 95% CI 3.33-3.65). Risk factors for an Apgar score <7 with a high crude OR and PAR were: nulliparity (OR 1.99, 95% CI 1.93-2.05, PAR=29.0%), prolonged second stage of labour (OR 1.94, 95% CI 1.87-2.00, PAR=12.1%), male sex (OR 1.28, 95% CI 1.24-1.31, PAR=15.4%), epidural analgesia (OR 1.48 , 95% CI 1.44-1.54, PAR=17.1%), induction of labour (OR 1.42, 95% 1.38 -1.47, PAR 8.2%), and meconium-stained amniotic fluid (OR 1.76, 95% CI 1.70-1.83, PAR=8.0%)).
For an Apgar score <4, the most notable risk factors were overall comparable to the risk factors for an Apgar <7. With a slightly stronger effect for non-western Ethnicity, non-cephalic presentation, and less effect of induction of labour.