Morning sickness is considered to be a good sign of a healthy pregnancy, and now scientists have provided an insight into why it occurs.
Morning sickness is the body's way of telling mums-to-be that she's eating the wrong things.
Scientists believe that it could just be an annoying by-product of a healthy pregnancy, as pregnant women and their embryos carry out a tug of war over the body's resources.
However, researcher Samuel Flaxman, an evolutionary biologist at the University of Colorado at Boulder said that if morning sickness was just the by-product of a healthy pregnancy, then it should accompany all healthy pregnancies. "But it doesn't."
Morning sickness often occurs at the sight, smell, or taste of meats and strong-tasting vegetables, which were historically likely to contain food-borne microbes or birth-defect-inducing chemicals, alcohol and cigarette smoke.
This suggests that the condition carries out a useful function, protecting mothers and embryos from things that may be dangerous.
Moreover, women experience morning sickness, specifically between week six and week 18 of pregnancy, when the embryonic organ development is most vulnerable to chemical disruption.
"To say that morning sickness is uncomfortable is a real understatement, and a lot of people are looking at ways to deal with it," Live Science quoted Flaxman, as saying.
"But if nausea and vomiting truly serve a useful function, then one has to look more carefully at strategies for dealing with these symptoms.
"We're really interested in a more exhaustive analysis to see if morning sickness really does only occur in human beings, or whether there are other animals out there," he added.
The study will appear in July issue of the journal American Naturalist.