A New Zealand study following more than 220 Christchurch children from birth to 12 years has found that abnormalities detected in the brains of some of those born very prematurely persist into late childhood and affect their motor skills, IQ, and social skills. However, a child’s family upbringing can help to buffer them from later risk.
Lead researcher Professor Lianne Woodward of the University of Canterbury (now based at Brigham and Women’s Hospital and Harvard Medical School in the US) and neonatologists Professor Terrie Inder and Associate Professor Nicola Austin, used MRI to scan the brains of 110 children born very prematurely – that’s less than 32 weeks’ gestation – and 113 children born full term at Christchurch Women’s Hospital from November 1998 to December 2000.
The early work, which led to Professor Woodward being awarded the Health Research Council of New Zealand (HRC) Liley Medal in 2006, showed that abnormalities within the developing white matter or ‘cabling networks’ of the brain after birth could potentially explain the motor and cognitive impairments often experienced by children born very prematurely.
“On MRI we could see subtle and diffuse abnormalities in the brain’s white matter that didn’t show up on ultrasound,” says Professor Woodward. “Because these were just tiny little babies whose brains were going to continue to develop, we needed to find out if these abnormalities would potentially lead to further changes in the brain or if the brain was able to repair and recover.”
To help answer this question, at term equivalent – between 39 and 41 weeks – the children were divided into four groups: those with no evidence of white matter abnormalities in the brain (27 percent), those with mild abnormalities (50 percent), moderate to severe abnormalities (17 per cent), and severe abnormalities (4 percent). The children then underwent comprehensive neurodevelopmental assessments at ages 2, 4, 6, 9 and most recently in 2010 to 2013, age 12.
In this latest study, funded jointly by the HRC and Neurological Foundation, the team found evidence that white matter abnormalities, as well as less mature grey matter development across both cortical and subcortical structures continued to be present in the brain at age 12.
Professor Woodward emphasizes that it is not just what a child’s brain looks like on their neonatal MRI that influences their development, but also the family social context in which they are raised.
In a paper that was recently accepted in the journal Child Development, the researchers used their longitudinal neurodevelopmental data to show that as the severity of early cerebral white matter abnormalities increased in these children, their IQ cognitive trajectory drops. Mild white matter abnormalities were associated with a 4-point drop in IQ, whereas moderate to severe white matter abnormalities lowered children’s average IQ by 18 points.
“We found that the extent of family social risk had an impact on children’s IQ trajectories, with each additional risk factor resulting in a 3-point drop in IQ. The children who fared the worst were those who had early neurological abnormalities on their MRI scan and were then raised in socially and economically disadvantaged family situations.”
“Our research shows that families have a very powerful influence on children’s development and that family socioeconomic resources and supportive parenting can help to buffer children from adverse outcomes following premature birth.”
The study has also identified important social challenges that children born very prematurely face.
“We found these children tended to have fewer friends, with around one in 10 saying they had no friends. They had less contact with their friends, and when they did it was more often through indirect forms of social interaction like Facebook rather than face-to-face contact like sleepovers and going to the mall on the weekend. This suggests that those friendships are qualitatively different or potentially less intimate, offering fewer opportunities for children to develop important social skills from their peers,” says Professor Woodward.
These children – particularly those born below 28 weeks – also had high rates of being picked on and bullied by their peers. This frequent victimisation was associated with poorer vision, delayed pubertal development, being overweight, and having hyperactivity problems.
“It’s not that being born premature makes you unpopular, but it’s the collection of developmental issues that come with being premature that predispose these children to having more social difficulties,” says Professor Woodward.
As part of the study, the team has developed a preschool screening strategy to identify those children born very prematurely who will likely go on to develop significant learning problems during their first four years of schooling.
“If children at a preschool assessment present with clinically significant problems in more than one of five important development domains – motor, socio-emotional, cognitive, language, and physical health – they have an extremely high chance of experiencing significant educational problems,” says Professor Woodward.
“We need to proactively identify these children from day one, to ensure their school progress is monitored and supported, rather than simply waiting until they have fallen way behind their peers in key skills such as reading and numeracy.”
Watch Lorelei Mason's report on this study on One News.
Background information:
The HRC has funded two projects in relation to this longitudinal study, both led by Professor Woodward. They are Neurological outcomes of very low birth weight infants at age 4 years (2003–2007, $286,567) and Neurological development of the preterm infant: A longitudinal study (2011–2016, $923,902).
Associate Professor Nicola Austin from Christchurch Women’s Hospital and Professor Woodward have also received funding from the Neurological Foundation to bring the children in this longitudinal study back at age 17 to track their health outcomes, including cardiac and respiratory health and psychosocial wellbeing and mental health. This study is now underway.