Original research
Low 5-minute Apgar score: a population-based register study of 1 million term births1,

https://doi.org/10.1016/S0029-7844(01)01370-9Get rights and content

Abstract

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.

Section snippets

Materials and methods

The study was based on data from the Swedish Medical Birth Registry, compiled of copies of medical records from antenatal care, delivery, and the pediatric examination of the newborn. It covers whole Sweden and contains data on 98–99% of all deliveries. A quality analysis of the register has been published.2

We analyzed data for 10 years (1988–1997) when 1,121,992 children were born according to official birth statistics, 98.9% (1,109,826) of whom were registered. Infants born before 37

Results

The study included 1,028,705 term infants of whom 7787 (0.76%) had 5-minute Apgar scores below 7 and 2155 (0.21%) below 4. The rate of infants with 5-minute Apgar score below 7 decreased from 0.77% in 1988 to 0.63% in 1992, then increased continuously to 0.82% in 1997 (Figure 1). An increased rate of low Apgar score during 1997 (OR 1.16, CI 1.07, 1.26) remained after excluding multiple births (OR 1.15, CI 1.06, 1.26), deliveries with epidural analgesia (OR 1.13, CI 1.02, 1.26), births of

Discussion

The Swedish Medical Birth Registry, providing data on 98–99% of births in Sweden, is one of the most complete birth registers in the world. We used the register to perform a population-based study on term infants with low Apgar score at 5 minutes after birth.

A low Apgar score is not a specific indicator of birth asphyxia because there may be other causes of this depression at birth. In this study, we excluded the two most apparent, prematurity and severe malformations. Biochemical markers,

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    This study was supported by grants from the Medical Faculty of Lund University, the Swedish Medical Research Council (Project No. 4732), the Axel and Margaret Axelsson-Johnson Foundation, the Royal Physiographic Society, First of May Flower Annual Foundation, and the Sven Jerring Foundation.

    1

    We are grateful to the National Board of Health and Welfare, Stockholm, Sweden, for providing data from registers, and greatly thank professor Bengt Källén at the Tornblad Institute for statistical advice.

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