Though it won't help your nausea, feeling sick is actually a good sign that your pregnancy hormone levels are high.
The exact cause of morning sickness is unknown, but it's thought to be connected to the pregnancy hormones human chorionic gonadotrophin (hCG) and oestrogen. The thyroid hormone thyroxine may also play a part.
Common causes of morning sickness are:
If you're expecting twins or triplets you will have higher levels of pregnancy hormones, and may be severely sick.
If you normally suffer from travel sickness, you may be more likely to feel sick when you are pregnant. That's because morning sickness may be linked to a disorder in the balancing mechanism in your inner ear.
If you already have a gastro-intestinal infection caused by a bacteria called helicobacter pylori, it may cause tummy upsets, ulcers and acid reflux. This can be identified through a poo sample test or blood test, and is easily treated with antibiotics that are safe to take in pregnancy.
If you are tired or hungry your nausea may become worse.
One theory is that your increased sense of smell and nausea is a protective measure. This makes you less likely to expose yourself to something that's unsafe to eat or harmful toxins.
Whatever the cause, it can be a shock to find yourself overwhelmed by morning sickness. It's unclear why some women get it and others escape, but seeing your pregnant friends enjoying their pregnancy may feel horribly unfair. It may help to remember that nothing you have done is causing your symptoms.
A few doctors still believe that morning sickness is a psychological condition, brought on by stress or negative feelings about your pregnancy. It's not a very popular theory. Most people believe that it's morning sickness which causes the stress, not the other way around.