Can Neonatal Morbidity and 2 Year Outcome Predict Cognitive Delay at 5 Years in Extremely Low Birth Weight (ELBW) Infants?

Special Article – Neonatology

J Pediatr & Child Health Care. 2017; 2(2): 1018.

Can Neonatal Morbidity and 2 Year Outcome Predict Cognitive Delay at 5 Years in Extremely Low Birth Weight (ELBW) Infants?

Agarwal P¹*, Lim WY², Yang PH¹, Rajadurai VS³, Khoo PC3, Quek BH³ and Daniel LM¹

¹Department of Child Development, KK Women’s and Children’s Hospital, Singapore

²Medical Innovation and Care Transformation, KK Women’s and Children’s Hospital, Singapore

³Department of Neonatology, KK Women’s and Children’s Hospital, Singapore

*Corresponding author: Pratibha Agarwal, Department of Child Development, KK Women’s and Children’s Hospital, 100 Bukit Timah Road, Singapore

Received: September 07, 2017; Accepted: October 24, 2017; Published: October 31, 2017

Abstract

Aim: To identify factors associated with cognitive delay in Asian ELBW survivors and evaluate the ability of significant delay at 2 years in predicting cognitive delay and need for rehabilitative services at 5.5 years.

Method: 213/295(72%) ELBW survivors were evaluated using the Mental Developmental Index (MDI) on the Bayley Scales of Infant Development (BSID II) and the Full Scale IQ (FSIQ) on Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) at 2 and 5.5 years respectively. Perinatal and neonatal factors associated with neurodevelopmental delay (MDI <70/ FSIQ scores <70) were estimated.

Results: Mean MDI and FSIQ scores were 77±18 and 89±13 respectively. 83 (39%) children had MDI<70, 20 (9%) had FSIQ<70. Thirteen (6%) had Neuro-Sensory Impairment (NSI) and 106 (50%) had major neonatal morbidity. On logistic regression, MDI<70 was significantly associated with lower birth weight [OR: 0.71(95% CI: 0.53-0.96)] and neonatal morbidity [OR 6.49 (95% CI: 2.95-14.21)]. Only NSI [OR: 15.36 (95% CI: 3.04-77.67)] and ethnic group [OR: 5.05 (95% CI: 1.06-23.94)] were independently significant in predicting FSIQ<70. MDI<70 had sensitivity of 0.81 specificity 0.65, positive predictive value 0.21 and negative predictive value 0.98 in predicting FSIQ<70. MDI<70 was independently associated with the need for rehabilitative services at 5.5 years (OR 5.52; 95% CI 2.59-11.76).

Conclusions: Neonatal morbidity was associated with delay at 2 but not at 5.5 years. NSI at 2 years was independently associated with significant cognitive delay at 5.5 years. Fewer ELBW survivors had significant delay at 5.5 years compared to 2 years. MDI<70 however predicted the need for rehabilitative services at 5.5 years.

What’s known on this subject: MDI score<70 at 18-30 months is used to define significant delay and neurodevelopmental impairment in ELBW infants.

Significant delay at 2 years is commonly used for long term prognostication and formulation of perinatal guidelines.

What this paper adds: Major neonatal morbidity was associated with developmental delay at 2 years of age whereas neurosensory impairment and ethnicity were associated with cognitive delay at 5 years.

MDI<70 at 2 years was a poor predictor of cognitive delay beyond 5 years but was associated with the need for extra assistance at 5.5 years.

Keywords: Neonatal morbidity; Cognitive; Infants

Introduction

The striking improvement in survival of Extremely Low Birth Weight (ELBW) infants has not been accompanied by consistent improvement in long term neurodevelopmental outcome in survivors [1-8]. Continuing high rates of neurodevelopmental impairment [1], impaired executive functioning and poor academic performance [9- 13], remain major concerns. The Bayley Scales of Infant Development (BSID, BSID-II and Bayley-III) are widely used for psychometric assessment in preterm Very Low Birth Weight (VLBW) children [6,10]. The Mental Developmental Index (MDI) from the BSID is commonly used in assessing the impact of neonatal intensive care, outcome of intervention [14-16], and formulation of perinatal guidelines [17].

Longitudinal follow up of preterm survivors is commonly limited to 24-30 months by cost and high attrition rates [18]. The ability of assessments at 2 years to precisely predict later cognitive function remains unclear. Roberts et al. [19] demonstrated a shift from no disability at 2 years to mild disability at 8 years, while a large proportion of children with moderate to severe disability at age 2 had improved at 8 years. Other longitudinal studies have also shown that early measures [20,21] are unduly pessimistic. However, a metaanalysis revealed a positive relationship between early MDI scores and later cognitive function [22] in VLBW children. Therefore, in this study, firstly, we aimed to identify factors associated with cognitive delay in a prospectively followed-up multi ethnic cohort of ELBW survivors and secondly, to further understand their developmental trajectory. We evaluated the predictive ability of an MDI score<70 in assessing cognitive delay and the need for rehabilitative services at 5.5 years.

Materials and Methods

This longitudinal cohort study was performed at the KK Women’s and Children’s Hospital in Singapore. Perinatal and neonatal data and follow up data was prospectively collected at 2, 5.5 and 8 years of age for ELBW survivors. Children with major congenital malformations were excluded. 213 ELBWs born between 2000 and 2004 and who completed assessments at both ages formed the study cohort (Figure 1). Of thirteen children excluded as they could not be assessed, 10 had NSI (cerebral palsy/deafness /blindness), one had selective mutism and nine needed extra assistance at 5.5 years. The hospital’s institutional review board approved the study.