Apgar Score Offers Prognostic Info for Neonatal Survival

Preterm infants with lower Apgar scores had an increased risk of neonatal death, according to a population study in Sweden.

Among babies born at 36 weeks or earlier, higher risk of mortality was seen among those born at lower gestational age and as Apgar scores decreased, with scores at 5 and 10 minutes predicting neonatal outcomes, Sven Cnattingius, MD, PhD, of the Karolinska Institutet in Stockholm, and colleagues reported in the New England Journal of Medicine.

The absolute rate difference -- the excess number of neonatal deaths per 100 births -- also increased as Apgar scores decreased in all gestational age ranges, they wrote.

Cnattingius and colleagues also found that an Apgar score that increased between 5 and 10 minutes was associated with lower rates of neonatal death compared with a stable score.

"Our findings challenge the view that the Apgar score may be of limited use in preterm infants," the authors wrote.

Some have argued that a low Apgar score in preterm babies may indicate biologic immaturity as opposed to fetal depression, they stated. "However, to the extent that physiological response patterns that are reflected by Apgar scores in preterm infants may be a proxy for vulnerability related to immaturity, Apgar scores may provide useful prognostic information for the survival of preterm infants."

Cynthia Bearer, MD, PhD, chief of the neonatology division at University Hospitals Rainbow Babies and Children's Hospital in Cleveland, said that, previously, providers did not think that Apgar scores were relevant to assess preterm babies.

"This paper shows that indeed it does have a predictive value for what babies are going to die within the first 27 days of life," Bearer, who was not involved in the study, told MedPage Today.

Apgar scores measure heart rate, respiratory effect, muscle tone, reflex irritability and color, and are used to assess the physical condition of newborns and the need for resuscitation, researchers wrote. The score was developed to assess infants born at term, and it typically decreases with gestational age due to biological immaturity.

For these reasons, Apgar score use to determine the condition of preterm infants has been questioned, researchers stated. The American Academy of Pediatrics has no specific recommendations for use among preterm babies.

Cnattingius and colleagues investigated the risk of neonatal death based on Apgar scores at 5 and 10 minutes according to gestational age.

They obtained data from more than 2.5 million births between 1992 and 2016, from the Swedish Medical Birth Register. They identified all preterm births, and linked birth data to the nationwide Swedish Cause of Death Register. Infants with congenital malformations were excluded from analysis.

Preterm births were stratified based on gestational age (22-24, 25-27, 28-31, 32-34, and 35-36 weeks), which was determined by an ultrasound for more than 80% of mothers in the study.

The authors adjusted for covariates including maternal age, parity, smoking status, BMI, hypertensive diseases, mode of delivery, birth weight, hospital level, year of birth and gestational age in days within each age range.

Of 113,300 preterm infants, there were 1,986 neonatal deaths. The mortality rate increased as gestational age decreased, from 0.2% among babies born at 36 weeks to 76.5% among those born at 22 weeks.

Low Apgar scores (0 to 3, or 4 to 6) at 5 minutes were more prevalent among babies born to mothers who had placental disruption or hypertension, delivered via cesarean section, and who had a low birth weight for gestational age.

Compared with babies with an Apgar score of 9 or 10, the risk of neonatal death was higher among those with the lowest Apgar score in all gestational age groups. But infants of an older gestational age had the highest relative risk.

Babies born at 22-24 weeks with an Apgar score at 5 minutes of 0 to 1 had nearly five times the relative risk of neonatal death compared with those who had a score of 9 or 10 (ARR 4.7, 95% CI 2.7-8.3). But among infants born at 35-36 weeks, the risk was more than 300 times higher (ARR 313.8, 95% CI 192.5-511.4).

The number of excess deaths per 100 births also increased as Apgar score decreased. Among babies born at 28-31 weeks, there were:

• Score of 0 or 1: 51.7 with score of 9 or 10 serving as the reference group (95% CI 38.1-65.4)
• Score of 2 or 3: 25.5 (95% CI 18.3- 32.8)
• Score of 4 to 6: 7.1 (95% CI 5.1-9.1)
• Score of 7 or 8: 1.2 (95% CI 0.5-1.9)

Cnattingius and colleagues noted that they did not have access to information on medical interventions during the initial stabilization, including whether or not infants were resuscitated, which may have influenced Apgar score values. In addition, as this research was conducted in Sweden, it was limited by the international variability in Apgar scoring.

Bearer said that understanding the predictive value of the Apgar score in this population may assist providers in educating families about the medical interventions available for preterm infants.

"I think it may be helpful in terms of counseling parents as to what sorts of actions will be taken in the delivery room," she said.

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