Association between Apgar scores of 7 to 9 and neonatal mortality and morbidity: population based cohort study of term infants in Sweden

Abstract

Objective To investigate associations between Apgar scores of 7, 8, and 9 (versus 10) at 1, 5, and 10 minutes, and neonatal mortality and morbidity. Design Population based cohort study. Setting Sweden. Participants 1 551 436 non-malformed live singleton infants, born at term (≥37 weeks’ gestation) between 1999 and 2016, with Apgar scores of ≥7 at 1, 5, and 10 minutes. Exposures Infants with Apgar scores of 7, 8, and 9 at 1, 5, and 10 minutes were compared with those with an Apgar score of 10 at 1, 5, and 10 minutes, respectively. Main outcome measures Neonatal mortality and morbidity, including neonatal infections, asphyxia related complications, respiratory distress, and neonatal hypoglycaemia. Adjusted odds ratios (aOR), adjusted rate differences (aRD), and 95% confidence intervals were estimated. Results Compared with infants with an Apgar score of 10, aORs for neonatal mortality, neonatal infections, asphyxia related complications, respiratory distress, and neonatal hypoglycaemia were higher among infants with lower Apgar scores, especially at 5 and 10 minutes. For example, the aORs for respiratory distress for an Apgar score of 9 versus 10 were 2.0 (95% confidence interval 1.9 to 2.1) at 1 minute, 5.2 (5.1 to 5.4) at 5 minutes, and 12.4 (12.0 to 12.9) at 10 minutes. Compared with an Apgar score of 10 at 10 minutes, the aRD for respiratory distress was 9.5% (95% confidence interval 9.2% to 9.9%) for an Apgar score of 9 at 10 minutes, and 41.9% (37.7% to 46.4%) for an Apgar score of 7 at 10 minutes. A reduction in Apgar score from 10 at 5 minutes to 9 at 10 minutes was also associated with higher odds of neonatal morbidity, compared with a stable Apgar score of 10 at 5 and 10 minutes. Conclusions In term non-malformed infants with Apgar scores within the normal range (7 to 10), risks of neonatal mortality and morbidity are higher among infants with lower Apgar score values, and also among those experiencing a reduction in score from 5 minutes to 10 minutes (compared with infants with stable Apgar scores of 10).

Associations between metabolic acidosis at birth and reduced Apgar scores within the normal range (7‐10): A Swedish cohort study of term non‐malformed infants

“…We considered both gestational age and birthweight for gestational age as confounders, given that both influence umbilical artery blood gases at birth and Apgar score values in term infants. 8,9,22,24 Mode of delivery is also associated with metabolic acidosis 25 and reduced Apgar scores. 9 However, an emergency caesarean section or vaginal instrumental delivery may be caused by (confirmed or suspected) fetal asphyxia.…”

“…1,8 Within term (≥37 weeks) non-malformed infants with normal Apgar scores (7-10) at 1, 5, and 10 minutes, we recently found inverse associations between Apgar scores and risks of neonatal mortality and morbidity. 9 Reduced Apgar scores of 7-9 at 10 minutes were generally associated with the highest risks. We and others have reported similar findings with respect to Apgar scores within the normal range and risks of long-term outcomes, including CP and epilepsy, 2 autism, 10 developmental physical or emotional vulnerability in childhood, 11 and increasing needs of education in special schools.…”

“…The primary objective of this study was to investigate associations between metabolic acidosis and risks of Apgar scores of 7, 8, and 9 at 5 and 10 minutes. We also estimated the joint impact of metabolic acidosis and Apgar score values within the normal range (7)(8)(9)(10), with respect to risk of neonatal morbidity. We also linked the database to the Swedish Neonatal Quality Register,…”

Apgar scores: Is anything less than perfect a cause for concern?

“…In order to further understand the association between Apgar scores and the risk of adverse outcomes, particularly among those infants without obvious concerning clinical signs at the time of birth, Cnattingius and colleagues 6 have performed a series of studies over the past few years focused on the outcomes of infants with Apgar scores ≥7. Leveraging population data from Swedish national registries, they have demonstrated that infants with lower normal Apgar scores (7‐9) have an increased risk of neonatal morbidity and mortality, and long‐term adverse outcomes including cerebral palsy and epilepsy 7 relative to infants with an Apgar score of 10.…”

“…These data seem to challenge the prevailing interpretation of Apgar scores of 7 or higher as “normal.” It should be kept in mind, however, that the absolute risk of neonatal mortality, cerebral palsy and epilepsy associated with low normal Apgar scores in the population of infants in these studies was small. For example, an Apgar score of 7 at 5 minutes was associated with a risk of neonatal death of 1 in 1000 6 and cerebral palsy of 3 in 1000 7 …”