Neurodevelopment outcome of low birth weights infants seen at the child assessment centre

Abstract

Neonatal intensive care units (NICU) were started in Queen Mary Hospital and Tsan Yuk Hospital in 1980. Children who were discharged from the units were followed by paediatricians. The Child Assessment Centre at the Duchess of Kent Children's Hospital was set up in 1986. Before 1992 the Centre received the majority of referrals for low birth weight who were high risk infants. In 1993, a low birth weight registry was set up and infants with birth weigh < 1.5 kg were referred. The objectives of this study were (1) to evaluate the neurodevelopmental outcome of all premature infants (< 3 weeks gestation) referred to the Child Assessment Centre; (2) to review the outcome of low birth weight (< 1.5 kg) seen in 1993 and 1994; (3) to identify perinatal risk factors; (4) to review any changes in the pattern of cerebral palsy. All premature infants were seen at the Centre between 1987 and 1996. The Griffiths Mental Developmental Scale was used for the first assessment. A General Quotient (GQ) score (scores of children under 2 years were corrected for prematurity RA) above 85 was considered normal, 70-85 as mild delay, 50-70 as moderate delay and below 50 as severe delay. Neurological examination was performed at first assessment and subsequent followup. At age 5 years, the children were assessed with the Hong Kong Wechsler Intellegence Scale for Children. A free field distraction test with visual enhancement was used to screen for hearing impairment. Tympangrams, audiograms and brainstem auditory evoked potentials were recorded for those with suspected hearing loss. Stycar mounted ball and 100s and 1000s were use for distant vision and near vision screening. The Cardiff Acuity Test, retinoscopy and VEP were used to assess children with suspected visual impairments. Cortical blindness, severe myopia, amblyopia are visual impairment. Statistical analysis was applied to identify perinatal risk factors for cerebral palsy. Mental handicap was divided into two main groups to evaluate outcome. Limited intelligence, mild mental retardation and mild delay were classified as minor mental handicap. Moderate and severe mental retardation, moderate and severe delay were classified under major mental handicap. There were 229 girls and 299 boys. Mean birth weight was 1.46 ± 0.58 kg (SD). Mean gestation period was 30 ± 3 weeks. The mean age of first assessment at the Centre was 20 ± 10 months with a mean GQ of 87 ± 24.7 using RA. Among 60 children with cerebral palsy, 35 (58%) had diplegia, nine (15%) had hemiplegia, nine had triplegia, and seven had quadriplegia. Mental function showed 12% minor mental handicap and 8% major mental handicap. Visual impairment was found in 24 (4.5%). Sensorineural hearing loss was found in 18 (3.4%) and 23 (4.3%) had epilepsy. Periventricular or intraventricular haemorrhage and the need for mechanical ventilation contributed to significant risk (P< 0.001) of developing cerebral palsy. Such haemorrhage was found in 128 (24%) children; 74 (14%) were grade 1 & 2, 54 (10%) were grade 3 & 4. Only one child developed cerebral palsy from those with grade 1 & 2, while 24 of those with grade 3 & 4 haemorrhage did. Before 1992 the overall handicap rate for cerebral palsy was 12.5%. From 1993-1994 the handicap rate for cerebral palsy was 9% and infants <1.5 kg who were born in Queen Mary and Tsan Yuk Hospitals had a physical handicap rate of 8.5%. The premature infants seen at the Child Assessment Centre before 1992 were high risk infants referred for assessment. This group of children had a minor mental handicap rate of 12% and 8% for major handicap. The rate of cerebral palsy has declined over the last 3 years, from 12.5% to 9%. This could be due to a better referral system or to improvement in neonatal care. Grade 3 & 4 intraventricular haemorrhage and a history of mechanical ventilation were identified as major risk factors for developing cerebral palsy.