Worldwide, the numbers of children who die before their fifth birthdays is on the decline. Still, millions of children are being lost to diseases and complications that are completely preventable.

In a study published earlier this week in the Lancet, researchers examined the reasons behind the 6.3 million deaths among children younger than 5 in 2013 — a number that’s significantly less than the 9.9 million such deaths that occurred worldwide in 2000. Nearly 2 million of the 2013 child deaths were due to complications from preterm birth and pneumonia, both of which were leading causes in 2000 as well. However, complications due to childbirth is now the third most common cause of child death, displacing diarrhea, which still a leading cause of child mortality, killing more children every day than AIDS, malaria and measles combined. Since 2000, child deaths due to measles, tetanus, HIV and diarrhea fell the fastest, with about half of the 3.6 million fewer child deaths occurring between 2000–2013 due to reductions in pneumonia, diarrhea and measles fatalities.

“We have seen huge successes, but there is still a long way to go,” said study author Robert Black, a professor in the Department of International Health at the Johns Hopkins Bloomberg School of Public Health, in a news release. “Millions of children are still dying of preventable causes at a time when we have the means to deliver cost-effective interventions. And if we don’t continue to devote research, resources and attention to the issue of child survival, we are going to lose the battle.”

To calculate the child mortality rates, researchers examined vital statistics records and oral autopsy data and used computer modeling to produce child death estimates for the World Health Organization’s 194 member states. The study found that sub-Saharan Africa is home to the largest burden of child mortality. About half of the 6.3 million child deaths in 2013 happened in sub-Saharan Africa, which is also predicted to be home to 60 percent of child deaths in 2030 if current trends stay the same. Overall, the three leading causes of child death in 2013 were preterm birth complications, pneumonia and intrapartum-related complications (emergencies during childbirth, such as birth asphyxia).

Nearly 52 percent of younger-than-5 deaths were due to infectious causes, with pneumonia, diarrhea and malaria at the top, the study found. The most common causes of neonatal death were preterm birth complications, intrapartum-related complications and neonatal sepsis or meningitis or other infections. The five countries with the highest numbers of children dying before age 5 were India, Nigeria, Pakistan, Democratic Republic of Congo and China. On a more positive note, southern Asia and sub-Saharan Africa were home to the largest reductions in deaths among children younger than 5.

The study notes that the worldwide Millennium Development Goal of reducing the death rate among children younger than 5 by two-thirds between 1990 and 2015 remains unmet and if trends stay the same, 4.4 million children will still die from often-preventable causes in 2030. However, if all countries were able to reduce their younger-than-5 mortality rate to 25 deaths per 1,000 live births, the estimated 2030 death rate could be cut nearly in half. The study also noted a “major transition” for child survival highlighted by the fact that preterm birth complications are now the leading cause of younger-than-5 deaths globally. Study authors Black, Li Liu, Shefali Oza, Daniel Hogan, Jamie Perin, Igor Rudan, Joy Lawn, Simon Cousens and Colin Mathers write:

A well-recognized shift is apparent in the timing of child deaths closer and closer to the time of birth. This shift is now happening all over the world, with 44% of child deaths in the neonatal period. Africa is the region with the lowest proportion of death in the neonatal period, partly because of specific postnatal and child causes, notably malaria and HIV. This shift is indicative of progress in reductions of infection deaths for children, and slow progress for neonatal mortality reduction and particularly preterm birth, for which prevalence is rising in many countries; even simple care is often scarce.

Scaling up health care services for newborns and to prevent preterm birth seem to be significant components of reducing global child death rates and though that’s a complex and multifaceted endeavor, the study notes that there are easy, low-cost places to begin. For example, a method known as “kangaroo mother’s care,” in which the newborn is placed on the mother’s chest to improve breathing and stabilize body temperature, costs nothing to implement and yet isn’t as widely used as it should be. Moving toward the future, the authors write that “disease-specific interventions are only part of the solution” — they also call for socioeconomic interventions, such as widening access to family planning services, which improves maternal health, and creating more opportunities for women’s education and socioeconomic development.

“Going forward, it’s going to be harder and harder to make the kind of headway we have seen in child deaths,” said lead study author Liu, an assistant professor in the departments of Population, Family and Reproductive Health, and International Health at the Bloomberg School of Public Health. “We have gone after some low-hanging fruit, but even in those areas there is still so much room for improvement. More, not fewer, resources are needed.”

To read the full child mortality study, visit the Lancet.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.