To decide whether childbearing is ethical or not, one needs to examine the diverse motives behind reproductive decisions.
Poor people sometimes have children solely for financial support from the government. In some countries such as Turkey and Sweden, parents receive family benefits for having children. If the motive behind the reproductive decision to have children is money, childbearing becomes unethical.
Parents may also consider children as an economic investment. They may have children only to get someone to support them in their old age. Such a selfish way of thinking makes having a child unethical in these cases.
In some cases where a diseased child needs cord blood from a sibling to survive, parents have a new child to benefit the other. If the parents were not planning on having any more children, and they are having the savior sibling only for the sake of the older child, then there is an ethical concern.
Even though the purpose of having a child is not for the sake of the parents, it is still for the sake of another individual. For this reason, the parental motive becomes selfish, and childbearing becomes unethical.
Some parents also have children for the sake of personal happiness. Having children has proven to be a great source of life satisfaction, self-esteem, and meaning. This fact especially applies to women.
According to Kantian ethics, it is morally wrong to use persons as mere means. To use someone as a mere means is to involve them in a scheme of action to which they could not, in principle, consent. In all the cases mentioned above, parents have children to use them as mere means. Therefore, childbearing is unethical in these cases.