Researchers have identified several possible causes of or contributors to stillbirth. However, in many stillbirths, the cause remains unknown even after extensive testing.
Beginning in 2003, NICHD supported the Stillbirth Collaborative Research Network (SCRN) to learn more about the possible causes of and contributors to stillbirth. This first-of-its-kind resource examined more than 500 stillbirths at 59 medical centers around the United States over 5 years. In almost one quarter of these cases, the researchers could not determine a probable or even a possible cause of death. Also, many of the stillbirths had more than one likely cause.
Although analyses of data from the SCRN continue, the research identified the following possible causes of stillbirth in the United States, in order from most to least common1:
- Pregnancy and labor complications, such as preterm labor; pregnancy with twins or triplets; and the separation of the placenta, which provides oxygen and nutrition to the fetus, from the womb (also called “placental abruption”).2 These were more common causes of stillbirths before 24 weeks of pregnancy.
- Problems with the placenta, such as insufficient blood flow.2 These were the leading causes of stillbirths in the womb, usually after 24 weeks of pregnancy.
- Fetal genetic problems and birth defects, such as the neural tube defect anencephaly, in which most or all of the fetal brain and skull fails to develop.2,3
- Infection in the pregnant person, in the womb, in the placenta, or in the fetus. Stillbirths from Escherichia coli, group B streptococcus, and enterococcus were most common. Infection-related stillbirths were more common before 24 weeks of pregnancy.
- Problems with the umbilical cord, such as when it gets knotted or squeezed, cutting off oxygen to the fetus.4 Umbilical cord problems were more likely to cause term stillbirths and those during labor and delivery.
- High blood pressure disorders, including chronic high blood pressure before pregnancy and preeclampsia. These problems were more common causes of late stillbirths and term stillbirths than of early stillbirths.
- Medical problems in the pregnant person, such as diabetes before pregnancy.
Racial Disparities in Stillbirth
In the United States, stillbirths are more than twice as likely among Black women than among White women.5 However, the reasons for this disparity are not entirely clear.
The SCRN study found that the most common causes of stillbirth were different for Black women than for White women and for Hispanic women. For non-Hispanic Black women in the SCRN, stillbirths were more likely to be caused by infection or by complications of pregnancy and labor. Also, the timing of stillbirth in Black women was different than that of White and Hispanic women: Stillbirths were more likely during labor and delivery and early (before 24 weeks) in pregnancy for non-Hispanic Black women.1
As mentioned previously, SCRN research found that the risk for stillbirth was higher among women who had experienced major financial, emotional, traumatic, or partner-related events in the year before delivery. Black women were more likely than women in general to have experienced at least three such stressful events in the past year, which could help explain some of the disparity.6 However, it is more likely that the higher number of stillbirths among non-Hispanic Black women results from a combination of risk factors and causes.