Only a minority of such cases receive any real attention from the media. Among these are those of Jessie Davis, LaToyia Figueroa, Bobbie Jo Stinnett, and Laci Peterson. The murdered pregnant women can also be found here at Wikipedia listed under their murderer's name.
Accurate statistics are difficult to obtain as "no reliable system is in place to track such cases." When the perpetrator is the alleged father of the developing fetus, it can be difficult to determine if the murder was at least partially motivated by the pregnancy, or was simply an act of shocking domestic violence that likely would have happened were she pregnant or not.
[T]he killings span racial and ethnic groups. In cases whose details were known, 67 percent of women were killed with firearms. Many women were slain at home -- in bedrooms, living rooms, kitchens -- usually by men they knew. Husbands. Boyfriends. Lovers.
Homicide is a gender-neutral crime, but is not the leading cause of death for women: "Nationally, homicide is a leading killer of young women—pregnant or not. In 1999, homicide was the second-leading cause of death among women ages 20 to 24. It was fifth among women ages 25-34. Accidents are the top cause of death in both age groups.
Isabelle Horon and Diana Cheng published a Maryland study in 2001 in the Journal of the American Medical Association which found "a pregnant or recently pregnant woman is more likely to be a victim of homicide than to die of any other cause." The suggestion that this is the primary cause of prenatal maternal death, however, again suffers a lack of fully reliable data.
In 2003, "California for the first time changed its death certificate process to include a female victim's maternity status, but no data are available yet" and it seems this remains the only state collecting such information.