Moms who spend part of their pregnancies vomiting and nauseated can take heart: Canadian research suggests they might actually have a smarter baby.

Researchers at Toronto's Hospital for Sick Children's Motherisk Program have discovered that morning sickness appears to be linked to enhanced neurodevelopment of the fetus.

Morning sickness, which affects as many as 80 per cent of pregnancies, is often one of the first signs of pregnancy, typically beginning around the second week of pregnancy. The name is a bit of a misnomer, since the nausea and vomiting that result can come on at any time of the day.

Morning sickness is little understood, but many doctors speculate it is the result of altered levels of hormones, such as estrogen, HCG (human chorionic gonadotropin), and thyroxine.

Nausea has long been known to be a sign of a healthy pregnancy; it's been linked to a lower miscarriage risk and a lower risk of heart malformations in the fetus.

While previous studies have focused on how pregnancy queasiness affects the outcomes of pregnancies, this is the first study to look at the long-term effects of the nausea on the cognitive skills of the babies that result.

For the study, 121 pregnant women were recruited between 1998 and 2003 through a morning sickness hotline run by the Motherisk program. Participants were split into three groups: mothers who experienced morning sickness and were treated with diclectin (a drug used to treat nausea and vomiting during pregnancy); those who experienced morning sickness and did not take diclectin; and those who did not experience morning sickness.

The intelligence and behaviour of the children of those pregnancies were then assessed when the kids were three years old and seven years old. The kids were given age-appropriate psychological tests, including measures of intelligence and behaviour.

Other factors such as mother's IQ, number of cigarettes smoked per day, alcohol consumption and socioeconomic status were also taken into account.

The study found that all children across the three groups scored within the normal ranges for neurodevelopmental outcome. But the children of women with morning sickness scored higher on performance IQ, verbal fluency, phonological processing and numerical memory.

Remarkably, the more severe the morning sickness, the more likely the children were to earn higher scores, the researchers found. They noted that maternal IQ also played a role in the outcome.

The results appear in the online edition of The Journal of Pediatrics.

Dr. Gideon Koren, the principal investigator of the study and the director of the Motherisk Program, says he knows that the study's conclusions sound "a little bit unusual," he insists it makes sense.

He explains that just as in ideal pregnancy, cells will divide and replicate properly to form the baby's physical structures, so will they grow properly to build a healthy brain.

"The same principles carry, it's just that we don't see it. We don't see a healthy brain. But the way to know about it is to test it with IQ tests," he told Canada AM.

He says the hormone swings that lead to morning sickness nausea are actually a good thing.

"It's the hormones secreted by the placenta that cause you to feel yucky, but on the other hand, they probably confer better conditions for the baby," he says. "Women suffer for it, but at least it's for a good cause."

Koren says the most important message pregnant women should take from the study is that diclectin, which is the only medication approved to help relieve morning sickness, is safe and effective.

"Many women are afraid to take medications during pregnancy. This study should empower them to take the medication," he says.

The study authors say that morning sickness is still puzzling and there is a need for further investigation into its causes. That could then help researchers come up with better ways to manage it.