Lower ‘normal’ Apgar scores linked to poorer outcomes
Author: Louise Prime
A lower Apgar score within the normal range at 1, 5, and 10 minutes is strongly associated with increased risks of neonatal mortality and morbidity, and even a small change in score between 5 and 10 minutes is also associated with adverse outcomes, research from Sweden has shown. The authors of the study,* published in The BMJ, said their findings provide strong evidence that the optimal Apgar score is 10 at each time point – so they argue that all newborns should be assigned an Apgar score at 10 minutes, regardless of their score at 1 minute and 5 minutes.
A team led from the Karolinska Institutet in Stockholm conducted a population-based cohort study among 1,551,436 non-malformed live singleton infants, born at term (≥37 weeks’ gestation) between 1999 and 2016, and with Apgar scores of ≥7 at 1, 5, and 10 minutes. They compared rates of several outcomes – neonatal mortality and morbidity, including neonatal infections, asphyxia-related complications, respiratory distress, and neonatal hypoglycaemia – between those babies with Apgar scores of 7, 8, and 9 at 1, 5, and 10 minutes and those with an Apgar score of 10 at 1, 5, and 10 minutes.
They reported that compared with babies with an Apgar score of 10, adjusted odds ratios (aORs) for neonatal mortality, neonatal infections, asphyxia related complications, respiratory distress, and neonatal hypoglycaemia were all higher among those with lower Apgar scores, especially at 5 and 10 minutes. For example, aORs for respiratory distress for an Apgar score of 9 versus 10 were 2.0 at 1 minute, 5.2 at 5 minutes, and 12.4 at 10 minutes. Compared with an Apgar score of 10 at 10 minutes, the adjusted rate differences (aRD) for respiratory distress was 9.5% for an Apgar score of 9 at 10 minutes, and 41.9% for an Apgar score of 7 at 10 minutes.
They also found that even a small change in Apgar score between 5 minutes and 10 minutes was associated with higher risks of neonatal morbidity. Compared with a stable Apgar score of 10 at both 5 and 10 minutes, reduction in Apgar score from 10 at 5 minutes to 9 at 10 minutes was associated with higher odds of neonatal morbidity including neonatal infections, neonatal hypoglycaemia, and respiratory distress – for example, a 4.1-fold higher odds of neonatal infections.
Furthermore, compared with Apgar scores of 10 at both time points, babies whose Apgar scores increased from 9 at 5 minutes to 10 at 10 minutes also had higher relative odds for all outcomes including neonatal mortality. For example, compared with Apgar scores of 10 at both time points, an improvement from an Apgar score of 9 at 5 minutes to 10 at 10 minutes was associated with a 1.8-fold higher odds of neonatal infections.
The researchers concluded: “Our study shows that low Apgar scores within the normal range (7 to 10) are strongly associated with neonatal mortality and morbidity and that these associations are substantially stronger with increasing time after birth. Additionally, a decrease in Apgar score from 10 at 5 minutes to 9 or less at 10 minutes is associated with a higher risk of neonatal morbidity.
“Our findings provide strong evidence to support the proposition that the optimal Apgar score is 10 at each time point, and all newborns should be assigned an Apgar score at 10 minutes, regardless of their score at 1 minute and 5 minutes.”
* Razaz N, Cnattingius S, Joseph KS. Association between Apgar scores of 7 to 9 and neonatal mortality and morbidity: population based cohort study of term infants in Sweden. BMJ 2019; 365: l1656 doi: 10.1136/bmj.l1656