Neonatal morbidity associated with late preterm and early term birth: the roles of gestational age and biological determinants of preterm birth

Hilary K Brown; Kathy Nixon Speechley; Jennifer Macnab; Renato Natale; M Karen Campbell

doi:10.1093/ije/dyt251

Neonatal morbidity associated with late preterm and early term birth: the roles of gestational age and biological determinants of preterm birth

Int J Epidemiol. 2014 Jun;43(3):802-14. doi: 10.1093/ije/dyt251. Epub 2013 Dec 27.

Authors

Hilary K Brown¹, Kathy Nixon Speechley², Jennifer Macnab³, Renato Natale³, M Karen Campbell⁴

Affiliations

¹ Department of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, CanadaDepartment of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada.
² Department of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, CanadaDepartment of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, CanadaDepartment of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada.
³ Department of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada.
⁴ Department of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, CanadaDepartment of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, CanadaDepartment of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, CanadaDepartment of Epidemiology and Biostatistics, The University of Western Ontario, London, Canada, Children's Health Research Institute, London, Canada, Department of Paediatrics, The University of Western Ontario, London, Canada and Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada Karen.Campbell@schulich.uwo.ca.

Abstract

Background: The aim of this study was to elucidate the role of gestational age in determining the risk of neonatal morbidity among infants born late preterm (34-36 weeks) and early term (37-38 weeks) compared with those born full term (39-41 weeks) by examining the contribution of gestational age within the context of biological determinants of preterm birth.

Methods: This was a retrospective cohort study. The sample included singleton live births with no major congenital anomalies, delivered at 34-41 weeks of gestation to London-Middlesex (Canada) mothers in 2002-11. Data from a city-wide perinatal database were linked with discharge abstract data. Multivariable models used modified Poisson regression to directly estimate adjusted relative risks (aRRs). The roles of gestational age and biological determinants of preterm birth were further examined using mediation and moderation analyses.

Results: Compared with infants born full term, infants born late preterm and early term were at increased risk for neonatal intensive care unit triage/admission [late preterm aRR=6.14, 95% confidence interval (CI) 5.63, 6.71; early term aRR=1.54, 95% CI 1.41, 1.68] and neonatal respiratory morbidity (late preterm aRR=6.16, 95% CI 5.39, 7.03; early term aRR=1.46, 95% CI 1.29, 1.65). The effect of gestational age was partially explained by biological determinants of preterm birth acting through gestational age. Moreover, placental ischaemia and other hypoxia exacerbated the effect of gestational age on poor outcomes.

Conclusions: Poor outcomes among infants born late preterm and early term are not only due to physiological immaturity but also to biological determinants of preterm birth acting through and with gestational age to produce poor outcomes.

Keywords: Preterm birth; neonatal intensive care; neonatal respiratory distress syndrome; pregnancy complications.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Canada / epidemiology
Female
Gestational Age*
Humans
Infant, Newborn
Infant, Newborn, Diseases / epidemiology*
Infant, Premature*
Intensive Care Units, Neonatal / statistics & numerical data
Male
Pregnancy
Pregnancy Outcome / epidemiology*
Premature Birth / epidemiology
Retrospective Studies
Risk
Sex Factors
Socioeconomic Factors
Term Birth

Grants and funding

GSD 104470/Canadian Institutes of Health Research/Canada