Morning sickness (also called "nausea and vomiting of pregnancy," or "NVP") affects between 50 and 85 percent of all pregnant women. It is not confined to the morning: nausea can occur at any time of the day. The cause is not known: some of the theories are:-

For 50% of all sufferers, it ends by the 16th week of pregnancy. Studies have shown that women who suffer from NVP are less likely to have miscarriages.