Aliya Visram is seven months pregnant and anticipating the birth of her second child. 

But the Toronto woman says pregnancy can also be a fearful time, as women try to decide what's best to do when faced with multiple sources of health advice.

"As mothers and mothers-to-be, we all want to do what's best for our babies and children," Visram said in an email.

Still, there are some strategies to cut through the confusion. 

This week's news that use of the popular pain reliever acetaminophen during pregnancy may increase the risk of behavioural problems in children is a recent example that could give some mothers-to-be pause for thought.

The acetaminophen paper is not the first to suggest an association between the use of a drug taken by thousands of pregnant women worldwide and the risk of harm to the developing brain. Many other studies suggest acetaminophen is safe.

"Two relatively large, well-done studies show a similar thing — maybe deserves attention," said Emily Oster, author of Expecting Better. "On the other hand, there's this tendency sometimes to overreact to what was the last thing you read on the internet."

Oster is an economics professor at Brown University in Providence, R.I. Reflecting on her pregnancy, Oster wished she'd been better prepared to make decisions she felt were thrust upon her by doctors with little time to consider the options.

The experience motivated Oster, an expert in evaluating statistical data, to devote more than a year to researching and writing the book.

"If you think about a question like 'Is it OK to have caffeine? You know, caffeine has been sometimes been linked to miscarriage.' I argue a lot in the book that those linkages are basically overstated and, in moderation, there's no excess risk. But there is a point which is if you think there's some excess risk and then you have a miscarriage and you had some coffee, I think it enhances people's feelings of guilt in a way that is sort of unfortunate."

Advice tuned out

The mixed messages emerging from studies of varying quality with different conclusions contributes to the confusion. 

At his family medicine practice in Toronto, Dr. Nav Persaud often gets questions from pregnant women about diet, exercise, medications or sexual activity. 

Women receive a lot of advice during pregnancy, some unwanted and some from reliable sources, he said.

"When you are being bombarded with different advice, it's difficult to know what to believe and who to listen to," said Persaud. "There is a tendency because it is confusing to just tune that advice out or, on the other hand, to unnecessarily avoid a lot of things."

As a researcher at St. Michael's Hospital in Toronto, Persaud fought to get access to unpublished clinical trial data about the popular morning sickness drug Diclectin

Since then, Persaud no longer refers pregnant women to commonly used resources, including from professional organizations, because he finds they can oversimplify a complex reality with categorical declarations of "safe" or "unsafe."

When you are being bombarded with different advice, it's difficult to know what to believe. -  Dr. Nav Persaud

In reality, the dose, exposure and stage of pregnancy, from planning to conceive through trimesters, all make a difference. 

"When a pregnant woman is asking you, 'Yes or no, should I drink coffee?' it's tempting to provide an answer," Persaud said. "But in the long term it's impossible for another person to weigh ... the value of benefits of coffee against the potential risks. Ultimately it is a trap to defer the decision to someone else because it's likely to lead to a bad decision for that individual woman."

For Persaud, there is no substitute from going to look at the original study itself. He recognizes that's practically impossible for many people. 

Oster's tips to cut through the cacophony in studies include: 

  • Compare probabilities in pregnancy with the risks women are often willing to take, such as driving a car
  • Take a  closer look at the risk. Studies often present risks as odds ratios, such as something increases the risk by five times. But it matters if it's the odds of something that's one in a million or one in 20.
  • Consider how believable the results of a study are. 

For the acetaminophen paper, Oster zeroed in on major differences between moms who said they took the drug and those who didn't, which could bias the results. Maternal history of psychiatric illness, which the study's authors took into account in their analysis, is one difference that jumped out at her. 

Drive to do best for baby

For Visram, a chiropractor who also works in prenatal and postnatal care, pain relief medications aren't necessarily bad. But she's seen pregnant women come to her fearful about how to deal with pains in the back, groin, hip and elsewhere.

Visram often recommends non-pharmacological approaches to pain, such as yoga. 

"I think building a relationship with your health-care practitioner, especially during pregnancy, is crucially important and is a great place to start when faced with conflicting information."