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Research Letter
January 2016

Association of Newborn Apgar Score With Maternal Admission to the Intensive Care Unit

Author Affiliations
  • 1Department of Medicine, St Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada
  • 2Keenan Research Centre, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada
  • 3Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada
  • 4School of Medicine, University of Toronto, Toronto, Ontario, Canada
JAMA Pediatr. 2016;170(1):88-89. doi:10.1001/jamapediatrics.2015.3035

The newborn Apgar score efficiently evaluates an infant’s condition at birth and the need for immediate attention.1 The risk of neonatal or infant death is greatest at a low 5-minute Apgar score of 0 to 3 and moderate at an intermediate score of 4 to 6 compared with a normal Apgar score of 7 to 10.13

The risk of neonatal and maternal mortality is highest when both the mother and infant are admitted to an intensive care unit (ICU) after delivery.4 Because the newborn 5-minute Apgar score is routinely collected, we assessed its association with maternal admission to the ICU.

Methods

We included 712 715 singleton obstetrical live births in Ontario, Canada, from April 1, 2006, to March 3, 2012, after excluding 99 735 births (12.3%) with missing or ineligible data. We explored whether a low, intermediate, or normal newborn Apgar score at 5 minutes is associated with maternal postpartum admission to the ICU. The study was approved by the Sunnybrook Health Sciences Centre research ethics board, and all data were deidentified.

Modified Poisson regression analysis was used to generate unadjusted and adjusted relative risks, controlling for maternal age, parity, income quintile, prepregnancy diabetes mellitus, obesity, drug dependence or tobacco use, and newborn sex. Results were stratified by preterm (24-36 weeks) vs term (≥37 weeks) delivery, the hypertensive disorders of pregnancy (gestational hypertension or preeclampsia), and findings above vs below the median time interval between delivery and ICU admission. We secondarily evaluated ICU admission with concomitant mechanical ventilation, which is an indicator of greater ICU severity (Damon Scales, MD, PhD, FRCPC; written communication; June 26, 2015). Data were analyzed from April 1, 2006, to March 3, 2012.

Results

Among mothers whose newborn had a normal 5-minute Apgar score, the rate of maternal ICU admission was 1.7 per 1000; the rate rose to 13.0 per 1000 with an intermediate Apgar score, and to 18.8 per 1000 with a low 5-minute Apgar score (Figure). The rates of ICU admission were high in women with preterm delivery or hypertensive disorders of pregnancy, but the adjusted relative risks were more pronounced for term births or in the absence of hypertensive disorders of pregnancy. The adjusted relative risks were also higher among women admitted to the ICU within 4 hours of delivery, especially for women also requiring mechanical ventilation (Figure).

Figure.
Relative Risk for Postpartum Maternal Admission to the Intensive Care Unit (ICU) Associated With the Newborn’s 5-Minute Apgar Score
Relative Risk for Postpartum Maternal Admission to the Intensive Care Unit (ICU) Associated With the Newborn’s 5-Minute Apgar Score

Crude (dark blue squares) and adjusted (orange squares) indicate relative risks for any maternal admission to the ICU, ICU admission with mechanical ventilation, and any maternal admission to the ICU stratified by timing of delivery, the hypertensive disorders of pregnancy, and time interval between the delivery and ICU admission. Relative risks (on a log scale) were adjusted for age, parity, income, prepregnancy diagnosis of diabetes mellitus, obesity, drug or tobacco use, and newborn sex. A low 5-minute Apgar score was defined as a score of 0 to 3; intermediate, 4 to 6; and normal (light blue squares), 7 to 10.

Discussion

A low 5-minute, newborn Apgar score reflects a higher risk of maternal ICU admission with and without mechanical ventilation. Existing clinical models of severe, acute maternal morbidity have moderate discrimination for predicting maternal end-organ injury or death within 30 days postpartum (C statistic, 0.66; 95% CI, 0.65-0.67).5 In high-resource settings, maternal admission to the ICU is a reasonable proxy for severe, acute maternal morbidity.4 A logical step is to evaluate whether the newborn Apgar score improves the discriminative performance of predictive models for severe, acute maternal morbidity, within a few hours of delivery and during the conventional 42-day postpartum period,4 and within high- and low-resource settings.

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Article Information

Corresponding Author: Joel G. Ray, MD, MSc, FRCPC, Department of Medicine, St Michael’s Hospital, University of Toronto, 30 Bond St, Toronto, ON M5B 1W8, Canada (rayj@smh.ca).

Published Online: November 2, 2015. doi:10.1001/jamapediatrics.2015.3035.

Author Contributions: Ms Park had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Ray, Park.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Ray, Medcalf.

Critical revision of the manuscript for important intellectual content: Ray, Park.

Statistical analysis: Ray, Park.

Obtained funding: Ray.

Administrative, technical, or material support: Ray.

Study supervision: Ray.

Conflict of Interest Disclosures: None reported.

Funding/Support: This work was supported by grant 201009 from the Canadian Institutes of Health Research (Dr Ray). Dr Ray holds a Canadian Institutes for Health Research Chair in Reproductive and Child Health Services and Policy Research.

Role of the Funder/Sponsor: The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: This study was completed at the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-term Care (MOHLTC). The opinions, results, and conclusions reported in this article are those of the authors and are independent from the funding sources. No endorsement by ICES, BORN (Better Outcomes Registry & Network), or the Ontario MOHLTC is intended or should be inferred.

Additional Contributions: We thank BORN for sharing their data with ICES.

References
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Casey  BM, McIntire  DD, Leveno  KJ.  The continuing value of the Apgar score for the assessment of newborn infants. N Engl J Med. 2001;344(7):467-471.PubMedArticle
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Montgomery  KS.  Apgar scores: examining the long-term significance. J Perinat Educ. 2000;9(3):5-9.PubMedArticle
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Iliodromiti  S, Mackay  DF, Smith  GC, Pell  JP, Nelson  SM.  Apgar score and the risk of cause-specific infant mortality: a population-based cohort study. Lancet. 2014;384(9956):1749-1755.PubMedArticle
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Ray  JG, Urquia  ML, Berger  H, Vermeulen  MJ.  Maternal and neonatal separation and mortality associated with concurrent admissions to intensive care units. CMAJ. 2012;184(18):E956-E962.PubMedArticle
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Bateman  BT, Mhyre  JM, Hernandez-Diaz  S,  et al.  Development of a comorbidity index for use in obstetric patients. Obstet Gynecol. 2013;122(5):957-965.PubMedArticle
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