J Korean Med Sci.  2015 Oct;30(Suppl 1):S35-S44. 10.3346/jkms.2015.30.S1.S35.

Risk Factors for Cause-specific Mortality of Very-Low-Birth-Weight Infants in the Korean Neonatal Network

• Lim JW
• Chung SH
• Kang DR
• Kim CR

• KMID: 2351134
• DOI: http://doi.org/10.3346/jkms.2015.30.S1.S35

Abstract

This study attempted to assess the risk factors for mortality of very-low-birth-weight (VLBW) infants in the neonatal intensive care unit (NICU, n=2,386). Using data from the Korean Neonatal Network, we investigated infants with birth weights <1,500 g and gestational ages (GAs) of 22-31 weeks born between January 2013 and June 2014. Cases were defined as death at NICU discharge. Controls were randomly selected from live VLBW infants and frequency matched to case subjects by GA. Relevant variables were compared between the cases (n=236) and controls (n=236) by Cox proportional hazards regression to determine their associations with cause-specific mortality (cardiorespiratory, neurologic, infection, gastrointestinal, and others). In a Cox regression analysis, cardiorespiratory death were associated with a foreign mother (hazard ratio, HR, 4.33; 95% confidence interval, CI, 2.08-9.02), multiple gestation (HR, 1.65; 95% CI, 1.07-2.54), small for gestational age (HR, 2.06; 95% CI, 1.25-3.41), male gender (HR, 1.69; 95% CI, 1.10-2.60), Apgar score < or =3 at 5 min (HR, 1.97; 95% CI, 1.18-3.31), and delivery room resuscitation (HR, 2.60; 95% CI, 1.53-4.40). An Apgar score < or =3 at 5 min was also associated with neurological death (HR, 2.95; 95% CI, 1.29-6.73). Death due to neonatal infection was associated with outborn delivery (HR, 5.09; 95% CI, 1.46-17.74). Antenatal steroid and preterm premature rupture of membranes reduced risk of cardiorespiratory death (HR, 0.43; 95% CI, 0.27-0.67) and gastrointestinal death (HR, 0.30; 95% CI, 0.13-0.70), respectively. In conclusion, foreign mother, multiple gestation, small gestation age, male gender, Apgar score < or =3 at 5 min, and resuscitation in the delivery room are associated with cardiorespiratory mortality of VLBW infants in NICU. An Apgar score < or =3 at 5 min and outborn status are associated with neurological and infection mortality, respectively.

Keyword

Infant, Very-Low-Birth-Weight; Mortality; Cause of Death; Risk Factors

MeSH Terms

Apgar Score
Cohort Studies
Databases, Factual
Female
Gestational Age
Humans
Infant
*Infant Death
*Infant Mortality/trends
Infant, Newborn
Infant, Premature
Infant, Very Low Birth Weight
Intensive Care Units, Neonatal
Kaplan-Meier Estimate
Male
Pregnancy
Pregnancy, Multiple
Proportional Hazards Models
Republic of Korea
Resuscitation
Risk Factors
Sex Factors

Figure

• 

  Fig. 1 Flow-chart identifying the study population.

• 

  Fig. 2 Survival curves by gestational age (22-31 weeks) up to a postnatal age of 300 days for 1,649 very-low-birth-weight infants admitted to the neonatal intensive care unit. Cum survival, cumulative survival; time, days of hospitalization after birth. Survival was estimated using the Kaplan-Meier method and Log-Rank test, P < 0.001.

• 

  Fig. 3 Survival curves by birth weight (220-1,499 g) up to a postnatal age of 300 days for 1,649 very-low-birth-weight infants admitted to the neonatal intensive care unit. Cum survival, cumulative survival; time, days of hospitalization after birth. Survival was estimated using the Kaplan-Meier method and Log-Rank test, P < 0.001.

• 

  Fig. 4 Categorical cause and timing of death according to postnatal age (n = 236). CAR, cardiorespiratory; NEU, neurologic; INF, infectious; GAS, gastrointestinal; OTH, others.

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  Fig. 5 Mortality rate, which is the number of deaths of infants per 100 live births, of causes of death according to GA of VLBW infants in the study group (n = 1,649). CAR, cardiorespiratory; NEU, neurologic; INF, infectious; GAS, gastrointestinal; OTH, others.

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