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Drug safety still confusing for pregnant women

OTTAWA — Tina Preseau began thinking for two last fall when she decided to have a baby. Armed with a copy of What to Expect when you're Expecting, advice from family and friends and scientific studies, she spent much of her time studying for a healthy pregnancy .


In November, Preseau became one of approximately 500,000 women who are pregnant in Canada each year and must wade through heaps of ambiguous research, wondering "Is this safe for my baby?"

Drugs during pregnancy
Conflicting drug research means difficult decisions for pregnant women.

"I never used to think about how everything I did was affecting me,"says Preseau, "but now it's all about the baby."

Excited to see a tiny set of 10 fingers and toes in August, Preseau is trying to avoid exposing her first baby to harmful substances that could cause birth defects.

Despite her doctor prescribing Diclectin, an anti-nausea drug used during pregnancy for 40 years in Canada, Preseau is resistant to join the estimated 80 per cent of pregnant women who use medication.     

'A pregnant woman might say 'I don't want to take anything' but she could be putting herself and her baby at even more risk'

"I'm not against it, but if I don't desperately need it, it's better not to take anything," says Preseau, who carries blue plastic bags in her wallet for emergency nausea bouts. "I'll try everything else before I take medication."

According to Motherisk, a Toronto-based research organization that counsels pregnant women on drug safety, women and their doctors must find a balance that will keep the mother healthy and the developing foetus at the lowest risk.     

Motherisk fields about 200 calls each weekday about the safety of drugs from over-the-counter cold remedies, to prescription medications for mental illness. 

Confusion prevails

With more research accessible than ever why are pregnant women still hesitant?

"It is very challenging," says Ellen Reynolds, director of communications for the Canadian Women's Health Network. "There is a lot of conflicting information out there."    

Barbara Mintzes, an assistant professor in the department of anaesthesiology, pharmacology and therapeutics at the University of British Columbia says some scientific studies are little more than marketing aids and add to the confusion.

"You'll have huge differences in what different studies might say partly because it's an area where there are strong financial interests at play," says Mintzes. "For trials sponsored by drug manufacturers, some that are planned in a way that it's clear the manufacturer will show an advantage for their drug."

Reynolds also says memories of the "thalidomide tragedy" make pregnant women think twice before popping pills.        

It's one reason Preseau says she doesn't want to take Diclectin despite her doctor's recommendation and supporting research. "I just can't get out of my mind the thalidomide babies," she says. "They said 'it's okay' and it turned out it really wasn't okay."     

Drugs crossing placenta

Drugs in the mother's blood can cross the placental membrane into blood vessels in the villi and pass through the umbilical cord to the fetus.

Reynolds says pregnant women should err on the side of caution.  "With thalidomide the effects were immediate at birth but with DES, it was subtle so the effects were only revealed 15 to 20 years later.  We can't be sure what we think is safe actually is," she says, "Precaution is the only sensible way to go." Thorough, long-term testing is needed to prevent another medical mistake, she says.

Finding the balance

While most researchers say pregnant women should be informed about which medications they use, not all agree that avoiding medication is the safest bet.     

"Not all drugs are thalidomide," says Myla Moretti, assistant director of Motherisk.  She says though using drugs can be dangerous, "the most dangerous thing a woman can do is make drastic decisions out of fear of the unknown ... Sometimes not treating is more dangerous than treating."

'I just can't get out of my mind the thalidomide babies. They says 'it's okay' and it turned out it really wasn't okay.'   

"Some conditions, if left untreated, can put the pregnancy at risk," Moretti says. "A pregnant woman might say 'I don't want to take anything' but she could be putting herself and her baby at even more risk." Even if a mom-to-be does everything right, she adds there's still a three per cent chance to have a birth defect.

Ethical considerations

Another reason why little is known about safe drug use during pregnancy, says Mintzes, is because researchers are ethically and legally reluctant to test drugs on pregnant women.  "For pharmaceutical companies the liabilities are higher for pregnant women," she says.

Thalidomide is now used in treating leprosy.

According to Moretti, by the time they hit the market, most drugs have not been tested for safety (or even effectiveness, adds Mintzes) in pregnancy.  This gives women who become pregnant access to thousands of medications, few of which have actually been proven safe or effective during pregnancy.  Moretti says medicating is a judgement call that must be made on a case-by-case basis between a woman and her doctor by balancing the potential risks with the potential benefits.     

Preseau says she is happy to keep her prescription in her wallet for now right next to the blue plastic bags. 

"You can't believe everything you read, especially with something so important," says Preseau. "You just have to take little bits and pieces of information from everywhere and hope you are doing the right thing."

Front Page Courtesy of The Anti-Stress Blog for Women

Related Links


Society of Obstetricians and Gynaecologists of Canada

Canadian Women's Health Network



The thalidomide tragedy

Between 1957 and 1962 thousands of women in 46 countries were prescribed a heralded miracle drug, a sedative that helped women sleep peacefully and forget about morning sickness.  However, many babies were born deaf, blind, with internal disabilities or disfigurations in their limbs.  This incident combined with diethylstilbestrol (DES)  a drug taken in pregnancy which in 1971 was linked to cancers which developed in mothers and children later in life proved that the placental barrier was not the impenetrable barrier it was previously thought to be.  


Risk categories for drugs
in pregnancy

A: Controlled studies in women fail to demonstrate a risk to the foetus, possibility of foetal harm appears remote.

B: Animal studies have not demonstrated a foetal risk, but there are no controlled studies in pregnant women

C: Studies in animals revealed potential adverse foetal effects and no human studies are available.

D: There is possible evidence of human foetal risk, but the benefits from use in pregnant women may be acceptable despite the risk.

X: Studies in animals or humans demonstrated foetal abnormalities. The risk of using this drug in pregnant women outweighs any possible benefit.

Source: Drugs in Pregnancy and Lactation, Sixth Edition



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