TORONTO — Pregnant women who snort, smoke or inject methamphetamines are also exposing their unborn babies to the potentially dangerous drugs, a landmark Canadian study has confirmed.

Researchers at Toronto's Hospital for Sick Children found evidence of methamphetamines in the hair of some newborns, demonstrating that when a mother-to-be uses crystal meth or another form of the drug, it is able to cross the placenta into the fetus.

Because fetal hair does not start growing until about the 20th week of pregnancy, evidence of meth in a newborn means it was not accidental exposure, said principal author Dr. Gideon Koren, head of Sick Kids' Motherisk program. That means the mother used the drug knowing she was pregnant.

"We know from our studies if it's used once, twice, you will not find it," Koren said of methamphetamine in the hair. (As well, blood and urine samples cannot determine long-term use or differentiate between various drugs.)

"It has to be persistent in the blood of mom in order to grow into the hair. That's a very, very ominous sign of addiction."

Methamphetamines, including crystal meth, are powerful stimulants that boost alertness and cause a rush of euphoria. But the highly addictive drugs also depress appetite, and in long-term users can lead to brain damage and psychotic behaviour.

Because crystal meth is relatively easy to make and buy - it can be cooked up in home laboratories with accessible ingredients and bought for $5 to $10 a hit - global use of the drug is skyrocketing, especially among young women, the researchers say. While national statistics for Canada are not readily available - figures vary from province to province - an estimated 500,000 Americans are believed to be regular users, including five per cent that are pregnant women.

The study, published online ahead of print in the fetal and neonatal edition of the Archives of Disease in Childhood, involved tests on hair samples from 8,000 mothers and newborns from across Canada that were sent to the Motherisk Laboratory for analysis between 1997 and 2005.

Almost 400 of the samples sent by doctors or children's aid societies tested positive for meth, including 11 mother and baby pairs. The first positive cases - six in all - were found in 2003. The next year, eight hair samples contained evidence of methamphetamine use. But in 2005, the number soared to more than 300.

"It's a looming epidemic, it's like a big black cloud," said Koren. "For sure we know that a significant group of Canadian kids have addicted mothers."

"I expect . . . we will see more and more."

Methamphetamine users were also more likely to use other drugs, the study found. In fact, 85 per cent of the 396 samples that came back positive for meth also tested positive for at least one other illegal drug, predominantly cocaine.

While the short-and long-term effects of methamphetamines on the developing fetus are not fully known, Koren said animal and small-scale human studies suggest the drug may affect normal growth and development.

The blood-brain barrier in a fetus is much more permeable than that of an adult, "so there's no question whatsoever that it goes into the brain of the baby," Koren explained. "There's all the theoretical reasons to believe it will have long-term effects on the babies."

"That's the next thing we're going to do - we will follow up these babies."

Wende Wood, a psychiatric pharmacist at the Centre for Addiction and Mental Health in Toronto, said babies whose mothers abuse drugs during pregnancy tend to be born prematurely and underweight.

It is difficult to tell, however, whether these babies are underdeveloped because of drugs or because the mother wasn't caring for herself properly during pregnancy, Wood said. A big problem for people taking methamphetamines is proper nutrition.

"With stimulants in particular, like meth and cocaine, they suppress the appetite. So a lot of the problems could be just as much from the poor self-care and poor nutrition as from the drug itself."

Dr. Heather Scott, a maternal-fetal medicine specialist at Nova Scotia's IWK Health Centre, said the study is important for several reasons, including its confirmation of the long-held suspicion that methamphetamines do enter the placenta and subsequently the developing fetus.

Knowing that may make doctors and other health providers more vigilant in trying to identify and help expectant mothers they suspect may be abusing drugs.

"My gut feeling - and this is strictly my gut feeling - is that (methamphetamine use) is on the rise, but I think we're not very good at getting a handle on it," Scott said Monday from Halifax.

Experts say methamphetamines are used by people from all socioeconomic levels - from street people looking for a cheap buzz to long-haul truck drivers who need to stay awake and even some "soccer moms" looking for a means of super-speed to keep up with the demands of work, family and social obligations.

"So I'm sure we're missing people who use the drug," said Scott of prenatal care providers, "because we never ask the question."

Wood said the study suggests a means for health providers to confirm suspected methamphetamine exposure in newborns - knowledge that could help them key in on potential developmental deficits in little ones, so that programs could be tailored to boost their development.

"Even if babies are born with problems, the post-natal period is so important and so much ground can be made up," she said.