Researchers solve mystery about 'rising' Canadian stillbirth rates

More than a decade ago, medical researchers noticed what seemed to be the start of a disturbing trend: Stillbirth rates were inching up in Canada, after many years of steady decline.

Stillbirths rose from six out of every 1,000 births in Canada in 2000, to 7.1 out of every 1,000 births in 2009, the latest year that national statistics are available.

Doctors speculated on what could be responsible for the rise. Some noted that women were waiting longer to have their first child. Others pointed out that a growing number of pregnant women were overweight or obese. Plus, a greater reliance on assisted-reproductive technology had led to more multiple births. Any one of these factors could compromise a pregnancy and increase the risk of stillbirth.

But now B.C. researchers have taken a fresh look at the issue and concluded that stillbirth rates are not rising after all. Apparently a false impression was created by the way in which births and deaths are recorded.

Their assessment, published Monday in the Canadian Medical Association Journal, is based on an analysis of all births in British Columbia between 2,000 and 2010. "The national data collection is not as detailed as it is at the provincial level. So we were able to drill down into the details," said the lead researcher, Dr. K.S. Joseph of the University of British Columbia.

He noted the apparent rise in stillbirths coincided with major advances in prenatal diagnosis. Blood tests, ultrasound images and other screening techniques have made it possible for doctors to monitor the progress of the developing fetus.

In a small faction of pregnancies, the tests will reveal a serious defect in which the child is not expected to survive very long after birth. It may be an inoperable heart problem or a neural-tube defect, such as anencephaly, in which part of the brain or skull is missing.

"If it is a very severe or lethal condition, the parents might choose to terminate the pregnancy," said Joseph.

Many of these diagnostic tests are carried out between 18 to 20 weeks, and the therapeutic abortions are performed around 20 and 22 weeks. That timing becomes critically important in terms of how these events are reported.

"The definition of a stillbirth is a baby who dies in utero and is delivered after 20 weeks, " explained Joseph. "So the pregnancy termination occurs at a time when we will have to fill out a stillbirth certificate."

In the past, these cases would have had another ending and become a different type of statistic. "The baby would have been born alive and might die in a few days or weeks. It would get counted as an infant death, instead of a stillbirth."

If the pregnancy terminations are removed from the stillbirth statistics "our rates are essentially flat or declining," said Joseph.

"The fact that [total stillbirth] rates are rising is not concerning. And it is not an indicator that maternal or fetal health has taken a downturn" said Joseph.

The study suggests that advances in prenatal diagnosis and an increase in pregnancy terminations have altered the timing of death of fetuses with congenital abnormalities.

Although the study is based on data collected in B.C., Joseph believes the findings apply to rates across Canada as well as other countries that use a similar method for charting live births and stillbirths.