This information is for women who have severe nausea and vomiting in early pregnancy. It tells you about steroids, a treatment used to relieve these symptoms. It is based on the best and most up-to-date research.
Do they work?
We're not sure. There's not enough good-quality research to tell us whether taking a steroid drug can stop severe vomiting in pregnancy (called hyperemesis gravidarum). We also can't say for certain that taking steroids is safe for your baby.
What are they?
Doctors call these drugs corticosteroids. They are not like the steroids used by bodybuilders. Instead, they are like some of the hormones your body makes naturally in your adrenal glands which help to lower stress.
Steroids aren't a standard treatment for severe vomiting in pregnancy. They tend to be used as a last resort.
Here are the steroids sometimes used to treat hyperemesis gravidarum. Most of the research has looked at steroid tablets, but steroids can also be given as injections.
How can they help?
We don't know whether they can help. Some research has found that if you have been in hospital for severe vomiting during pregnancy, steroids can reduce your chances of having to go back for more treatment.  But steroids don't reduce vomiting.
How do they work?
Steroids work well in treating other kinds of nausea and vomiting, such as nausea after chemotherapy for cancer.  But we're not sure exactly how they work.
Can they be harmful?
Studies involving more than 100,000 women found no increase in the number of major malformations in babies whose mothers took steroids during the first 12 weeks of pregnancy. 
Some recent studies showed a small increase in the chances of babies developing cleft palates if their mothers took steroids during the first 12 weeks of pregnancy.  But researchers don't know for certain as there isn't enough evidence.
There are also side effects if you take steroids for a long time when you are pregnant.  They include:
About 1 in 20 people find that steroid tablets affect their mood.  This can happen a few days or weeks after you start treatment. You may be irritable, anxious, or confused, or have trouble sleeping. Or you can get an unusually high mood (euphoria). Rarely, people get more serious side effects, such as thinking about suicide or seeing things that aren't really there. It's also possible to get these side effects when you stop taking steroids.
Your doctor should explain the benefits and risks of steroids before you start taking them. Doctors are advised to use steroids in pregnancy only if the benefits of treatment outweigh the risks to the baby. 
If you get any worrying symptoms while you're taking steroids, see your doctor straight away.