The risk of neonatal mortality among preterm infants increases with decreasing Apgar score values across gestational ages, Swedish researchers found.
In addition, changes in Apgar scores between 5 and 10 minutes help predict survival.
Sven Cnattingius, MD, PhD, Karolinska Institutet, Stockholm, Sweden, and colleagues concluded that Apgar scores provide prognostic information concerning neonatal survival among preterm infants.
The Apgar score was developed in the 1950s as a method to assess the physical condition of newborns — as well as their response to resuscitation — based on five criteria (Appearance, Pulse, Grimace, Activity, Respiration) rated on a scale of 0-2. An accumulation of all 5 values results in the final Apgar score, with normal Apgar scores commonly defined as the 7-10 range. The scores are routinely measured at 1, 5, and 10 minutes after birth in Sweden.
According to Cnattingius and colleagues, while gestational age is the major determinant of neonatal mortality in preterm infants, the association between gestational age, the Apgar score, and the risk of neonatal mortality is unknown. They also pointed out that since the frequency of low Apgar scores increases with lower gestational ages, this may reflect greater biologic immaturity in these infants. “The value of the Apgar score to assess the condition of the preterm infant has therefore been questioned,” the authors wrote.
Here, in a study published in The New England Journal of Medicine, the authors evaluated the association between the risk of neonatal death and Apgar 5- and 10-minute scores, as well as the change in the Apgar score from 5 to 10 minutes in preterm infants, according to gestational age.
Cnattingius and colleagues used data from the Swedish Medical Birth Register to identify 113,300 preterm infants (between 22 weeks and 36 weeks, 6 days of gestation) born from 1992 through 2016. They further stratified those infants according to gestational age (22 to 24 weeks, 25 to 27 weeks, 28 to 31 weeks, 32 to 34 weeks, and 35 or 36 weeks) and estimated the adjusted relative risks of neonatal death, and absolute rate differences in neonatal mortality, according to 5- and 10-minute Apgar scores, as well as the change in the Apgar score between 5 minutes and 10 minutes.
The rate of neonatal mortality among the study population was 1.8%, ranging from 0.2% at 36 weeks’ gestation to 76.5% at 22 weeks’ gestation. Low Apgar score values (under 7) at 5 and 10 minutes were most common among the infants with a gestational age of 22 to 24 weeks, with the percentage of infants with low scores gradually decreasing as the gestational age increased.
The authors determined that the relative risk of neonatal death increased with decreasing Apgar score at 5 minutes, and that the relative risk increased markedly among infants at older gestational ages. For example, of infants born at 22 to 24 weeks, those with an Apgar score of 0 or 1 had about 5 times the relative risk of neonatal death as those with an Apgar score of 9 or 10. However, infants born at 35 or 36 weeks with an Apgar score of 0 to 1 had a relative risk that was more than 300 times higher than those with Apgar scores of 9 or 10.
Cnattingius and colleagues also found that lower Apgar scores were associated with substantially greater absolute rate differences in neonatal mortality. For example, with infants who had an Apgar score of 9 or 10 at 28 to 31 months serving as the reference group, the adjusted absolute rate differences in neonatal mortality, according to the 5-minute Apgar score, were 51.7 for infants who had a score of 0 to 1, 25.5 for a score of 2 or 3, 7.1 for a score of 4 to 6, and 1.2 for a score of 7 or 8.
They also determined that increases in Apgar scores between 5 minutes and 10 minutes are associated with lower neonatal mortality compared with scores that remained stable. This “may reflect a better health status at 5 minutes in infants whose scores subsequently increased than in those whose scores did not increase,” wrote Cnattingius and colleagues. However, they added, “this may be valuable prognostic information.”
According to the authors, the study’s results support the hypothesis that Apgar scores are useful in evaluating the health of newborns across all gestational ages and “challenge the view that the Apgar score may be of limited use in preterm infants.”
The study authors noted that the variability of assessing the Apgar score from both the interobserver and international perspective could be considered a limitation of the study.
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The risk of neonatal mortality among preterm infants increases with decreasing Apgar score values, across gestational ages. Additionally, changes in Apgar scores between 5 and 10 minutes are also associated with neonatal mortality in preterm infants.
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Thus, these scores at 5 and 10 minutes do have prognostic value concerning neonatal survival among preterm infants.
Michael Bassett, Contributing Writer, BreakingMED™
The study was supported by a grant from the Swedish Research Council for Health, Working Life, and Welfare and by an unrestricted grant from Karolinska Institutet, Stockholm.
Cnattingius had no disclosures.
Cat ID: 138
Topic ID: 85,138,791,730,102,838,138,683,192
