Almost 29,000 babies in Canada in 2006-2007 were born pre-term. (CBC)

The rate of pre-term births in Canada has increased since the early 1990s, according to a report released Thursday.

Early birth may result in possible long-term physical effects on the children, as well as extra costs to the health care system.

The report "Too Early, Too Small: A profile of small babies across Canada," by the Canadian Institute for Health Information, looked at the number of babies born pre-term, delivered before 37 weeks gestation.

"Factors such as delayed child-bearing and use of reproductive technologies are likely contributing to a greater number of multiple births and pre-term deliveries," said Jean-Marie Berthelot, CIHI's vice-president of programs.

In 2006-2007, the Canadian pre-term birth rate was 8.1 per cent, or almost 29,000 births, up from around 6.6 per cent in the early 1990s, the researchers found.

The rate of small-for-gestational-age births — babies born with a weight below the 10th percentile for their gestational age and sex — was 8.3 per cent, down from approximately 11 per cent in the early 1990s.

'Concerning' trend

"I know the trends. But as a clinician I am surprised that with advanced medical care, with improved screening, with a decrease in [maternal] smoking, that it's still increasing," said Dr. Mark Walker, a high-risk obstetrician at the Ottawa Hospital and a spokesperson for the Society of Obstetricians and Gynaecologists.

"So it's concerning."

Babies born pre-term or small-for-gestational age are at an increased risk of long hospitalizations and complications.

Biological factors such as a mother's age were more strongly linked with pre-term births. Women aged 35 and older had a one in 10 chance of delivering a pre-term baby in the year studied, compared to eight per cent for those 20 to 34.

C-section, health issues cited in rise

Women with high blood pressure or diabetes were six times more likely to deliver pre-term than women without those conditions, which are linked to obesity.

"With the understanding that chronic conditions can increase the chances of having a pre-term birth sixfold, additional management of these conditions throughout a pregnancy becomes a vital step in limiting the instances of pre-term births," said Dr. Reg Sauve, a professor in community health science at the University of Calgary.

The pre-term birth rate was also higher for babies delivered by caesarean section at 13.3 per cent compared to induced births at 6.9 per cent or non-induced vaginal deliveries at 6.5 per cent.

Babies conceived through fertility treatments are more likely to be born pre-term than those conceived naturally, Walker said.

The growth in twins and triplets that has coincided with the introduction of assisted reproductive technologies may also be contributing to pre-term births. Multiple-birth babies were nearly 17 times as likely to be born pre-term as single babies, according to the report.

Hospital costs higher too

Mothers living in low-income neighbourhoods were at 1.5 times an increased risk of having a baby who is small for gestational age, compared to mothers living in high-income areas, the researchers found.

Likewise, mothers living in urban areas were 1.3 times or 30 per cent more likely to have a baby who is small for gestational age.

In cost terms, in 2005-2006, the average in-hospital cost for a low birth-weight baby — less than 2,500 grams or 5½ pounds — was more than 11 times higher than for those weighing 2,500 grams or more.

That translates into an average of $12,354, compared to $1,084 for a normal-weight baby.

The cost of care for single pre-term babies was on average nine times higher than for full-term babies — $9,233 versus $1,050.

The report also includes data on C-section and epidural rates for vaginal deliveries in different provinces.

With files from the Canadian Press