shown that age, mental health, and substance use, and a personal history of abuse may serve as risk factors of child abuse. At the level of society, factors contributing to child maltreatment include cultural norms that encourage harsh physical punishment of children, economic inequality, and the lack of social safety nets. WHO and ISPCAN state that understanding the complex interplay of various risk factors is vital for dealing with the problem of child maltreatment. Factors related to relationships include marital strife and tension. Parents who physically abuse their spouses are more likely than others to physically abuse their children. However, it is impossible to know whether marital strife is a cause of child abuse, or if both the marital strife and the abuse are caused by tendencies in the abuser. Parents may also set expectations for their child that are clearly beyond the child's capability (e.g., preschool children who are expected to be totally responsible for self-care or provision of nurturance to parents), and the resulting frustration caused by the child's non-compliance may function as a contributory factor of the occurrence of child abuse. Most acts of physical violence against children are undertaken with the intent to punish. In the United States, interviews with parents reveal that as many as two thirds of documented instances of physical abuse begin as acts of corporal punishment meant to correct a child's behavior, while a large-scale Canadian study found that three quarters of substantiated cases of physical abuse of children have occurred within the context of physical punishment. Other studies have shown that children and infants who are spanked by parents are several times more likely to be severely assaulted by their parents or suffer an injury requiring medical attention. Studies indicate that such abusive treatment often involves parents attributing conflict to their child's willfulness or rejection, as well as "coercive family dynamics and conditioned emotional responses". Factors involved in the escalation of ordinary physical punishment by parents into confirmed child abuse may be the punishing parent's inability to control their anger or judge their own strength, and the parent being unaware of the child's physical vulnerabilities. Children resulting from unintended pregnancies are more likely to be abused or neglected. In addition, unintended pregnancies are more likely than intended pregnancies to be associated with abusive relationships, and there is an increased risk of physical violence during pregnancy. They also result in poorer maternal