The causes of morning sickness revealed

Laura Mappas
Monday, January 4, 2010
Causes of morning sickness. Image: Getty

Sign of a healthy pregnancy
Believe it or not, morning sickness may actually be good for pregnant women and their unborn babies.

Scientists have long known that the nausea and vomiting normally experienced in early pregnancy points to a healthy pregnancy, but what they don't know is whether the sickness actually serves a purpose, or whether it's just an annoying by-product of having a healthy baby.

Protecting mother and baby
Researcher Samuel Flaxman from the University of Colorado at Boulder, in the US, argues that if morning sickness was just a by-product of a healthy pregnancy, then it should accompany all healthy pregnancies, "But it doesn't," says Flaxman. While two-thirds of pregnant women experience the sickness, the remaining one-third don't — and of that one-third, many still carry their pregnancies to term.

So if morning sickness is not just a by-product of a healthy pregnancy and if it does, in fact, have an actual cause and purpose, what is it? Flaxman and his colleague Paul Sherman from Cornell University in New York believe the irritating illness has to do with a woman's body's natural instinct to protect her unborn child.

It makes sense — morning sickness is usually triggered by the sight, smell or taste of certain foods, and these foods that pregnant women suddenly find repulsive are things such as cheese or meats — foods that were historically more likely to contain food-borne microbes or birth defect-inducing chemicals. Likewise, the taste or smell of alcohol and cigarettes is also usually enough to make a pregnant woman's stomach turn. So, what this suggests is morning sickness does actually have a function — to protect mothers and embryos from things that are potentially harmful.

Adding more fuel to the morning-sickness-has-meaning fire, is that most women experience the tell-tale nausea in early pregnancy, with symptoms tending to peak between week six and week 18 when the embryo's organ development is the most susceptible to chemical disruption.

Managing morning sickness
Understanding the whys and wherefores could have some very real benefits for pregnant women who are bearing the brunt of the never-ending hangover that is morning sickness.

Flaxman agrees: "To say that morning sickness is uncomfortable is a real understatement, and a lot of people are looking at ways to deal with it. But if nausea and vomiting truly serve a useful function, then one has to look more carefully at strategies for dealing with these symptoms."


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