In addition to risk factors that can increase the likelihood of a stillbirth, there are also factors that can cause or contribute to stillbirth. Remember, though, that in some cases of stillbirth, the cause of death remains unknown even after extensive testing.
To learn more about the possible causes of and contributors to stillbirth, the NICHD-supported Stillbirth Collaborative Research Network (SCRN) examined more than 500 stillbirths that occurred in 59 medical centers around the United States over 2½ 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.
The likely causes of and contributors to stillbirth identified by the study are listed below in order from most common to least common:1
- Pregnancy and labor complications. Problems with the pregnancy likely caused almost one in three stillbirths. These complications included preterm labor, pregnancy with twins or triplets, and the separation of the placenta from the womb (also called “placental abruption;” the placenta provides nutrients and oxygen to the fetus). Pregnancy and labor complications were more common causes of stillbirths before week 24.
- Problems with the placenta. Almost one in four stillbirths were likely caused by problems with the placenta. One example of a placental problem that causes stillbirth is insufficient blood flow to the placenta. In the SCRN study, placental problems were the leading cause of stillbirths that took place before birth, and these deaths tended to occur after 24 weeks of pregnancy.
- Birth defects. In more than 1 of every 10 stillbirths, the fetus had a genetic or structural birth defect that probably or possibly caused the death.
- Infection. In more than 1 of every 10 stillbirths, the death was likely caused either by an infection in the fetus or in the placenta, or by a serious infection in the mother. Infections were a more common cause of death in stillbirths before week 24 than in those after.
- Problems with the umbilical cord. Problems with the umbilical cord were considered a probable or possible cause of about 1 in 10 stillbirths. For example, the cord can get knotted or squeezed, cutting off oxygen to the developing fetus. This cause of stillbirth tends to occur more toward the end of pregnancy.
- High blood pressure disorders. High blood pressure in the mother—whether due to chronic high blood pressure or to preeclampsia—also contributed to stillbirths. These types of stillbirths were more common in the end of the second trimester and the beginning of the third, compared with other parts of pregnancy.
- Medical complications in the mother. Problems with the mother’s health—such as diabetes—were considered a probable or possible cause in fewer than 1 in 10 of the stillbirths.
This research also showed that:
- Women who experienced financial, emotional, or other personal stress in the year before their delivery had an increased chance of having a stillbirth.
- Smoking tobacco or marijuana, taking prescription painkillers, or using illegal drugs during pregnancy is associated with double or even triple the risk of stillbirth.
In the United States, stillbirths are more than twice as likely among black women than among white women.2 However, the reasons for this are not entirely clear.
The SCRN study found that the most common causes of stillbirth were different for black women than for white women. Compared with stillbirths experienced by white women and Hispanic women, stillbirths to non-Hispanic black women tended to be caused by infection or by complications of pregnancy and labor. Also, in black women, stillbirth was more likely to occur during (rather than before) labor and earlier than 24 weeks into the pregnancy.1
As mentioned above, SCRN research found that stillbirth was more than twice as likely among women who had experienced major financial, emotional, traumatic, or partner-related events in the year before delivery than among women who had not. Black women were more likely than women in general to have experienced at least three such stressful events in the past year.3