Extremely low birth weight (ELBW) infants are vulnerable to numerous adverse perinatal factors in their early life. The effects of such perinatal factors on later motor performance in non-disabled ELBW children is uncertain, and is the focus of this series of longitudinal studies.
Children who were born <1000 g between 1992-1994 at Mater Mother’s Hospital and lived within 250 km from the testing centre, were included in this study. They were excluded if diagnosed with neurological and intellectual impairment. Of 105 eligible children, only 48 of them had a complete set of data available for all studies. Participants (27 males) had a birth weight of 784.2 (±146.9) gm, and a gestational age of 26.9 (±2.0) weeks. The children’s mean age at assessments were: 52.8 (±2.6) weeks at the 12 month assessment, 4.1 (±0.1) years at the 4 year assessment and 12.4 (±0.7) years at the 12 year assessment. Ethical approval was gained from the University of Queensland and Mater Mother’s Hospital.
Perinatal factors identified from the literature including: multiple birth, gestation, birth weight, gender, prolonged rupture of the membranes, pre-eclampsia, antepartum hemorrhage, antenatal steroids, Caesarean section, Apgar score at 1 minute, respiratory distress syndrome, chronic neonatal lung disease (CNLD), patent ductus arteriosus (PDA), necrotizing enterocolitis (NEC) grade 2A/3B, intracranial hemorrhage grade 3-4, periventricular leukomalacia, retinopathy of prematurity and sepsis were included in this study.
Standardized measures of motor outcomes at 1, 4 and 12 years, as well as fitness, behaviour and competency at 12 years were extracted from charts. Motor performance at 1 and 4 years was assessed using the Neuro-Sensory Motor Development Assessment (NSMDA). The Motor Assessment Battery for Children (MABC) first edition was used to assess participants’ motor performance at 12 years. Fitness (VO2max) was calculated from a 20 m shuttle run test at 12 years. Behaviour and social competency scores were derived from the Child Behavior Checklist (CBCL) completed by parents.
Study I: Perinatal Factors In Non-Disabled ELBW School Children And Later Performance.
At 12 years of age, the MABC categorized 32 of 48 participants as suspected/ abnormal. Normal/ abnormal category on the MABC at 12 years was significantly related with perinatal factors of gender (p=0.005) and CNLD (p=0.013). Multiple regression analysis showed motor outcome at 12 years to be independently related to male gender (p=0.03) and CNLD (p=0.045). Sixty-five percent of children were identified as unfit. CNLD was significantly related to cardiorespiratory endurance (VO2max) (p=0.03) and multiple regression analysis showed it was independently related to VO2max at 12 years (p=0.05). No perinatal factors were significantly related to respiratory function variables.
Study II: Perinatal factors and Motor Performance at 1 and 4 Years, in Non-Disabled ELBW Survivors
Of 48 participants, 17 and 23 were classified by the NSMDA as having minimal to moderate dysfunction at 1 and 4 years of age respectively. CNLD, NEC and PDA had associations with NSMDA category (normal/abnormal) at 12 months. CNLD, male gender and NEC had associations with NSMDA category at 4 years. On multiple regression analysis, CNLD and NEC were independently associated with abnormal motor outcome at 12months.
Study III: Relationship between perinatal factors and behaviour and competency in non-disabled ELBW survivors
Only five of 48 participants were within clinical range on the total behavior problems scale of the CBCL. In internalizing and externalizing scales, five and two children were within the clinical range respectively. The main findings identified the effect of gender and other perinatal factors (birth weight, NEC, CNLD, prolonged rupture of membranes and sepsis) on some behaviours and competency. No group mean values for any behaviour or competency for this ELBW cohort were within the clinical range. With regards to behaviour performance, boys performed significantly poorer than girls in the broadband areas of total behaviour and internalizing scales. In the individual syndrome scales, boys performed less well than girls in the areas of somatic complaints and social problems. Stratification within the ELBW group, found that ELBW’s weighing <750 gm at birth performed poorer than ELBW ≥750 gm on externalizing scale. Interestingly children with a history of sepsis performed better than those without sepsis on broadband scales of internalizing, and on individual syndrome scales of withdrawn and anxious/depressed. With regards to competency scales, children with a history of PROM had poorer activities scores than those without PROM. Boys were also scored by their parents to have less participation (activities scale) than females. On the overall competency score, children with a history of CNLD and NEC were found to have lower competency than those without CNLD and NEC. NEC also has been found to have an impact on social competency scale, with those with a history of NEC performing more poorly than those without NEC.
The results of the studies indicate that non-disabled ELBW children with a history of CNLD are at risk of having minor motor problems at 1, 4 and 12 years. Males are also at greater risk of having mild motor, fitness and behavior problems. Behaviour is a complex issue affected by many factors. The impact of perinatal factors on behaviour at 12 years is less clear than the motor and fitness outcomes reported. Even so, generally, male gender and those with history of NEC, CNLD and PROM are likely to have behaviour problems and low competency. Thus this series of studies has shown that long term follow up of otherwise healthy ELBW is important, and that careful screening of these children is crucial to identify minor motor difficulties, fitness and behavioural problems. This would allow specific and objective programs of physical therapy intervention to be introduced based on specific motor performance and overall development.