Actually I think you need to think whether you mean 'morally' or actually 'ethically'.
Ethically it is wrong to kill any child (I personally don't buy the not-human/not-living etc arguments) whether born or not. That is the basic ethical principle of non-maleficence - "do not harm". But that principle can also be applied to the mother, future implications for the child, the child's family and society in general. Also you have to weigh the ethical principle of beneficence - "doing good" - and that is relevant to the mother's rights and health.
What that means is that there is no definitive answer and that every case has to be judged on its own merits to determine the total efficacy for all concerned.