Morning sickness can occur at any time of the day, although early morning is a common time.
Sickness can start before you miss your first period, but it's typical to feel much better after three months. Not everyone's so lucky - some women are sick throughout their pregnancy.
It's believed pregnancy hormones cause the sickness. These circulate in the body, affecting all your organs and preparing your body to sustain new life.
One theory is that your body is protecting the foetus from harmful substances. In fact there's research to show how women who experience bad sickness are less likely to miscarry, and the sickness generally stops when the baby's major organs have developed.
Small, frequent snacks can help alleviate the symptoms. Avoid large meals, especially those high in fat, as they will put a greater strain on your digestive system.
Don't let your stomach remain empty for more than a couple of hours. Have a dry crispbread, cracker or piece of plain toast to keep your system ticking over.
Keep dry crackers by your bed and eat one or two before getting up in the morning. If you wake in the night, have a small snack to help prevent sickness in the morning. Fruit or savoury foods seem to be better at preventing nausea than sweeter snacks.
Go with any cravings you have (within reason). Ginger has been shown to help relieve sickness. It's safe to use in pregnancy and you can take it in several forms - ginger tea, ginger ale or ginger biscuits.
Some women find that acupressure bands help.
You should talk to your doctor if your sickness is affecting your overall health, if you find you can hardly keep food or drinks down, or if you become extremely tired.
Extreme pregnancy sickness, or hyperemesis gravidarum, might even mean a hospital stay to allow you to maintain fluid levels and prevent dehydration. Drug treatment is available in some cases.
Pregnancy sickness, even severe sickness, is not associated with any harm to your baby.