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Small babies born preterm at much higher risk of neonatal death


Neonatal mortality is 100 times higher for infants born preterm who are also severely underweight for their gestation age, according to a new study from the Institute for Clinical Evaluative Sciences (ICES) and St. Michael’s Hospital.

Babies born preterm (PTB) are at known to be at higher risk of neonatal mortality, as are babies born small (underweight) for gestational age (SGA). A pregnancy affected by the combination of PTB and SGA (“PTB-SGA”) typically has more underlying placental dysfunction, and expected worse neonatal outcomes.

The researchers showed that, while PTB and SGA are each known risk factors for neonatal mortality, the combination of PTB-SGA significantly increases that risk.

“Preterm birth and small for gestation age– separately and combined – are significant predictors of neonatal death. We need to focus on methods to detect and prevent these conditions,” says Dr. Joel Ray, lead author on the study and a researcher at ICES and the Li Ka Shing Knowledge Institute of St. Michael's Hospital.

PTB is defined as a birth before 37 weeks of gestation. For this study, the researchers defined severe SGA as a birthweight below the 5th percentile. Neonatal mortality is a death during the first 28 days of life.

The study, published today in the journal Peditatrics, is the first to look at infants with both PTB and severe SGA.

The researchers looked at nearly 1.7 million births in Ontario hospitals between April 1, 2002 and March 3, 2015, and examined the data to determine the risk of neonatal death in relation to PTB alone, severe SGA alone, or PTB-SGA together, each compared to births with neither PTB nor SGA. During the study period of 13 years, the researchers found:

  • The rate of neonatal mortality is six deaths per 10,000 in infants without PTB or severe SGA
  • The  rate of neonatal mortality is 28 deaths per 10,000 in infants born at term with severe SGA
  • The rate of neonatal mortality is 229 per 10,000 infants born PTB without severe SGA
  • The rate of neonatal mortality is 600 per 10,000 infants with PTB-SGA

“Neonatal mortality was nearly 100 times higher among infants born preterm with severe SGA than those born at term with a birthweight over the 5th percentile – which equates to an additional 59 neonatal deaths per 1000 livebirths,” says Ray. “PTB-SGA serves as a useful perinatal surveillance indicator in high- and low-income countries, given its ease of measurement and its prediction of neonatal death.”

“Mortality in infants affected by preterm birth and severe small-for-gestational age birth weight,” was published today in Pediatrics.

Author block: Joel G. Ray, Alison L. Park and Deshayne B. Fell.

The Institute for Clinical Evaluative Sciences (ICES) is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on Twitter: @ICESOntario

About St. Michael’s Hospital

St Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future healthcare professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the Hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael’s Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

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