14 December 2011

Causes and risk factors for stillbirth

A systematic evaluation of what may have led to a stillbirth will uncover a probable or possible cause in most cases.


A systematic evaluation of what may have led to a stillbirth will uncover a probable or possible cause in most cases, according to a report in the Journal of the American Medical Association (JAMA) from the Stillbirth Collaborative Research Network (SCRN).

"The global message would be to encourage families to do an evaluation for possible causes of stillbirth because you can find a cause in about three quarters of cases," corresponding author Dr Robert M Silver from the University of Utah in Salt Lake City said.

"The most important part of the evaluation would be an autopsy and an evaluation of the placenta and genetic testing of the baby," he said.

Yet in the US, "very few women undergo a complete evaluation for stillbirth and the proportion of cases that have autopsy is alarmingly low, it's less than 20%", Dr Silver noted.

A companion paper from the SCRN, also published in JAMA, shows that risk factors for stillbirth can be identified early in pregnancy or even before pregnancy and many of these factors are modifiable.

The corresponding author on the second paper, Dr George Saade from the University of Texas Medical Branch at Galveston, said: "Women with any of these risk factors may need additional surveillance during pregnancy."

In their paper, Dr Silver and colleagues report that complete postmortem examinations of 512 neonates stillborn at 20 weeks gestation or later revealed a probable cause of death in 312 (61%) and a possible or probable cause of death in 390 (76%). In 161 cases (31%) there was more than one probable or possible cause of death.

Common causes of death

The researchers say obstetric complications were the most common category for cause of death (150 cases; 29%); placental abnormalities were implicated in 121 cases (24%).

Other causes included foetal genetic/structural abnormalities in 70 cases (14%), infection in 66 (13%), umbilical cord abnormalities in 53 (10%), hypertensive disorders in 47 (9%), and maternal medical complications in 40 (8%).

Compared with non-Hispanic white women and Hispanic women combined, non-Hispanic black women experienced a higher proportion of stillbirths associated with obstetric complications (43% vs 24%) and infections (25% vs. 8%).

Cord abnormalities were associated with a higher proportion of stillbirths in non-Hispanic white and Hispanic women compared with non-Hispanic black and other women, they note.

In the companion paper, Dr Saade and colleagues report that various risk factors known at the time of pregnancy may help gauge the risk of stillbirth. The findings are based on prenatal, intrapartum, and neonatal information on mothers and neonates, including 614 stillbirths and 1816 live births.

Risk of stillbirth

Their study confirmed several known risk factors for stillbirth, including previous stillbirth, maternal diabetes, maternal age of 40 or older, obesity, smoking, multifoetal pregnancy and non-Hispanic black race. They also identified increased stillbirth risk for women pregnant for the first time or living alone.

For the most part, however, risk factors present at the beginning of pregnancy (apart from previous stillbirth or pregnancy loss) had low positive predictive value and were associated with relatively few stillbirths, limiting the opportunities for early intervention, according to the report.

The co-authors of a commentary published with the studies say stillbirth has until recently been a "neglected topic" in perinatal medicine despite its frequency.

Conservative estimates put the number of stillbirths worldwide at more than 2.6 million in 2008, write Dr Jay D Iams and Dr Courtney D Lynch, from The Ohio State University Medical Center in Columbus.

The two reports from the SCRN, they say, provide "lessons about the causes of foetal death, opportunities to prevent stillbirth, and the implications for stillbirth research for all adverse pregnancy outcomes".

(Reuters Health, Megan Brooks, December 2011)

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