Low 5-minute Apgar score: a population-based register study of 1 million term births

OBJECTIVE: To determine the rate of 5-minute Apgar scores below 7 in term infants (at least 37 weeks) in Sweden during 1988-1997, evaluate the influence of obstetric risk factors on low 5-minute Apgar scores, and to study the infant prognosis regarding infant mortality, neonatal neurologic morbidity, and outcome. METHODS: Data were collected from the Swedish Medical Birth Registry 1988-1997, and the National Hospital Discharge Registry. Odds ratios (OR) and risk ratios were calculated. RESULTS: Among 1,028,705 term newborns, 7787 (0.76%) had 5-minute Apgar scores below 7. The annual rate of low Apgar scores decreased from 0.77% in 1988 to 0.63% in 1992, but thereafter increased to 0.82% in 1998. The highest OR was found for vaginal breech delivery (OR 6.7), birth weights above 5 kg (OR 6.3), and second born twins (OR 4.1). Primiparity, maternal age, smoking, post-date pregnancy, epidural analgesia, male infant gender, and being born at night, were also significant risk factors for Apgar below 7 at 5 minutes. The infant mortality rate was 48 per 1000 (OR 14.4), and the ORs were 31.4 for a diagnosis with cerebral palsy, 7.9 for epilepsy, and 9.5 for mental retardation. CONCLUSION: Several obstetric risk factors are associated with low 5-minute Apgar score in term infants. Mortality and the risk of severe neurologic morbidity are increased in these infants.