What is the leading cause of death world wide?
The World Health Organization reported, from May 24, 2018, that there were 56.9 million human deaths worldwide in 2016. 
Of these Ischaemic Heart Disease and Stroke are at the top with 15.2 million deaths.
Chronic obstructive lung disease – 3 million deaths.
Lower respiratory infections – 3 million
Dementia – 2 million
Lung and airway cancers -1.7 million
Diabetes – 1.6 million
Road injuries – 1.5 million
Diarrhea illnesses – 1.4 million
Tuberculosis – 1.3 million
Total of these top 10 reported causes of human death is 30.7 million.
A review of a number of sources on the internet estimate there are more than 40 million induced abortions every year world wide. I did not find a total estimate on the World Health Organization Website. They do say there were 25 million unsafe abortions each year between 2010 and 2014. And they say 45 % of all abortions those years were unsafe, leading to a total estimate of 55.5 million abortions annually. This means those who estimate around 40 million are unlikely to be exaggerating. So, there are more than 40 million abortions annually. 
Conclusion: The leading cause of human death annually worldwide is abortion by far. The number of abortions annually is far greater than the number of deaths of the top ten causes of death added all together.
A question: If we want to prevent the greatest number of deaths at the lowest cost where should be apply our resources? 
 Regarding the financial cost of preventing abortion, some may be tempted to factor in the cost of supporting the children that would reach live birth if not abort into the cost effective equation. But this concern should be countered by the benefit of the work all of these people be able to do. There is a growing concern that some countries are headed for financial disaster because they are not having enough live children.
I believe if one takes into account the negative emotional cost born by those who abort their children, anything done to reduce the number of abortions will be very cost effective.
If one takes into account the spiritual cost of what is required by the judge who the Bible says all will stand before after they die, prevention of abortion is likely infinitely more cost effective than all other death prevention programs.