In a new study published Friday, the Centers for Disease Control and Prevention reported that over half of adult female homicide victims were killed by a current or former intimate partner. The study also found that non-Hispanic black women and American Indian/Alaska Native women experienced the highest homicide rates.

The study compiled data from 10,018 homicides of women aged 18 or older in 18 U.S. states between 2003 and 2014. The data was taken from the CDC’s National Violent Death Reporting System, which monitors and collects information on violent deaths across the country.

A total of 55.3 percent of adult female homicides were related to intimate partner violence (IPV), the study found. Among these homicides, 79.2 percent were perpetrated by a current partner and 14.3 percent were committed by a former partner. (The remaining 6.4 percent of victims were killed in relation to an intimate partner violence situation but not by their own intimate partner.)

The report states that jealousy was a known factor in about 12 percent of the IPV-related homicides, and that 11.2 percent of the IPV-related homicides were preceded by some form of violence in the victim’s life within a month of their death (though not necessarily committed by the same perpetrator). In nearly 30 percent of the IPV-related deaths, an argument preceded the homicide.

Rape or sexual assault was involved in 11.1 percent of the IPV-related homicides and 11.2 percent of the non-IPV-related homicides. Of the victims who were not killed in an intimate partner violence situation, 19.7 percent were killed by an acquaintance, 15.7 percent were killed by a stranger and 15.2 percent were killed by a parent. About 15 percent of all female homicide victims between the ages of 18 and 44 were pregnant or had given birth within 6 weeks of their death.

Firearms were involved in over half (53.9 percent) of the deaths. This was most common in the deaths of non-Hispanic black victims (57.7 percent). Non-Hispanic black women experienced the highest homicide rate (4.4 per 100,000 individuals, compared to 2 per 100,000 for all women) while American Indian/Alaska Native women experienced the second highest (4.3 per 100,000).

The perpetrators in 98.2 percent of the IPV-related homicides were male, compared with 88.5 percent in non-IPV-related homicides. Previous data, from the Federal Bureau of Investigations, showed that men were more likely than women to be both victims (78.8 percent) and perpetrators (89 percent) of homicide.

Another previous report by the Bureau of Justice Statistics stated that 40 percent of female homicide victims were killed by intimate partners in 1993, and that this number rose to 45 percent in 2007. In 2007, only 5 percent of male homicide victims were killed by intimate partners. Female victims were killed by intimate partners at twice the rate of male victims in 2007.

The CDC’s National Intimate Partner and Sexual Violence Survey, published in April 2017, found that 1 in 4 women and 1 in 9 men had experienced some form of intimate partner violence.

The CDC report on adult female homicide concludes that several strategies could be implemented to protect women from IPV-related homicide, including: training for first responders and medical professionals to detect IPV and refer suspected victims to intervention services and other resources such as housing and legal advocacy; bystander intervention training for individuals to recognize and safely intervene in situations of interpersonal violence; limiting the ability of those under domestic violence restraining orders to have access to firearms and; developing programs and policies to prevent intimate partner violence before it occurs.