Babies born premature and of small birth weight are more likely to be abused or neglected, research suggests.
Bigger babies tend to be more healthy
The findings are based on almost 120,000 children born between 1983 and 2001 who were placed on the child protection register.
The reason is unclear but researchers speculate smaller children might provoke greater parental hostility.
The University of Warwick study is published in the Journal of Epidemiology and Community Health.
Children are placed on the register if they have already endured physical and/or emotional abuse and neglect.
The register may also include children who have not been sexually abused, but who live in a household with a registered sex offender.
The study of babies placed on the register in West Sussex showed that whatever the type of abuse, lower birth weight children and those with a shorter gestational age were more likely to be placed on the register.
The smallest babies were more than twice as likely to be placed on the register as the largest.
The findings held true even after adjusting for levels of deprivation and age of the mother at birth - both of which are known to influence the length of pregnancy and a baby's birth weight.
The researchers admit their study was not designed to look for the association which they uncovered.
But they suggest a number of possible reasons why the two could be linked.
They say that pre-term infants, or those with poor foetal growth, may have characteristics that make them more vulnerable to abuse.
Premature births and low birth weight are both linked to an increased risk of a range of health problems, including mounting evidence of behavioural disorders, such as depression.
The researchers, led by Professor Nick Spencer, say it might be that this makes them less easy to manage, or less responsive.
Writing in the journal, they say: "It is possible that such infants may be more likely to provoke hostile parental feelings.
'Prevention strategy needed'
"Early separation, more commonly experienced by pre-term and small for gestational age infants, may interfere with parent-infant bonding, although this is unlikely to be an important factor except at the extremes."
Alternatively, they speculate that mothers who are more likely to abuse their children may also be more likely to carry a child that fails to thrive.
They go on to say: "Strategies and interventions aimed at preventing child abuse need to take account of the association with poor foetal growth and short gestational duration."
Diana Sutton, of the National Society for the Prevention of Cruelty to Children, said: "This research makes an important contribution to our understanding of why some children are at increased risk of abuse.
"It is deeply sad that children already particularly vulnerable through low birth weight and premature birth could face abuse too.
"Although the authors make clear that further research is needed into this area, health professionals should be aware of this study and its implications for preventing child abuse.
"It is important that effective support is given to families who are affected in this way."