Here is what Wikipedia reports as the causes of child abuse:
Child abuse is a complex phenomenon with multiple causes. Understanding the causes of abuse is crucial to addressing the problem of child abuse. 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.
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 mental health, and lower mother-child relationship quality.
Substance abuse can be a major contributing factor to child abuse. One U.S. study found that parents with documented substance abuse, most commonly alcohol, cocaine, and heroin, were much more likely to mistreat their children, and were also much more likely to reject court-ordered services and treatments. Another study found that over two-thirds of cases of child maltreatment involved parents with substance abuse problems. This study specifically found relationships between alcohol and physical abuse, and between cocaine and sexual abuse.
Unemployment and financial difficulties are associated with increased rates of child abuse. In 2009 CBS News reported that child abuse in the United States had increased during the economic recession. It gave the example of a father who had never been the primary care-taker of the children. Now that the father was in that role, the children began to come in with injuries.
A 1988 study of child murders in the US found that children are 100 times more often killed by a "non-biological parent (e.g. step-parent, co-habitee or boyfriend/girlfriend of a biological parent)" than by a biological parent. An evolutionary psychology explanation for this is that using resources in order to take care of another person's biological child is likely not a good strategy for increasing reproductive success. More generally, stepchildren have a much higher risk of being abused which is sometimes referred to as the Cinderella effect.
Psychologists conducted a study in the United States in 2010 which examined over 200 regular church attendees from eleven different denominations of Christianity, most of whom were educated, upper-middle class White Americans, found that extrinsic religious orientation was associated with a greater risk of physical child abuse. Those with a more extrinsic religious orientation who also adhered to greater social conformity were particularly more likely to share characteristics with physically abusive subjects. Subjects who adhered to Biblical literalism exhibited a higher potential of physical child abuse. Those who had a more intrinsic religious orientation were not found to be at a greater risk of child abuse, although they sometimes exhibited greater social conformity or a greater propensity for holding literal interpretations of the Bible. Approximately 85% of the study's subjects were parents.
I included all the factors suggested as contributing to child neglect and child abuse because clearly there are many causes besides unintended pregnancies. However, unintended pregnancies and some of the other common factors, which are in bold type, do seem to go hand in hand.
Some people might have viewed my childhood as one where I was abused and maybe neglected. I was not the result of an unintended pregnancy. My parents were mostly financially sound. My mother was a stay-at-home mom, for the most part.
Both my biological parents were substance abusers. My parents separated when I was 4 years old. My father was unemotional and remote to me during the short time I spent with him. My mother was often physically and emotionally abusive to others, including me. However, I certainly did not suffer the worst abuse she could dole out. She reserved that for my stepfather.
Unlike my stepfather, I fought back when she was abusive to me, by blocking her punches and slaps and yelling right back at her when she was being verbally abusive to me. I vacated this abusive/dysfunctional household when I was 16 years old. Fortunately, I also had many very positive experiences growing up which I prefer to recall and which certainly helped shape my good life as an adult.