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morning sickness

Alternative Names
nausea and vomiting in pregnancy, hyperemesis gravidarum

Morning sickness is nausea or vomiting during the first 20 weeks of pregnancy. More than half of pregnant women have morning sickness during the first trimester. It usually goes away by the second trimester. When morning sickness is severe, it is called hyperemesis gravidarum.

What is going on in the body?
The cause of morning sickness is not well understood, but hormones seem to be involved. The hormone called human chorionic gonadotropin, or HCG, is produced by the fertilised egg and by the chorionic villi. These are the fingerlike projections of the developing placenta. HCG is needed to keep the pregnancy going until the placenta has developed enough. HCG levels are usually highest in the first 12 weeks of pregnancy.

What are the signs and symptoms of the condition?
There is a huge variation in how bad the symptoms of morning sickness are. Some women just feel queasy in the morning, and feel fine by noontime. They are able to perform their daily activities. Others suffer from nausea and vomiting that can last all day. They find ordinary work during pregnancy almost impossible.

Some women have symptoms of morning sickness within days of conception. But the average time from the last menstrual period to the start of nausea is about 5 weeks.

The symptoms of morning sickness include: What are the causes and risks of the condition?
A woman with high levels of HCG is more likely to have morning sickness. High levels of HCG are seen in multiple pregnancies, such as twins and triplets. A woman who has had morning sickness in a previous pregnancy is more likely to have it again.

Increased HCG levels can be caused by a tumour of the placenta called hydatidiform mole. This condition should be ruled out in women with morning sickness. Other possible causes include pancreatitis, bowel disease, and vitamin deficiency. There is some evidence that psychological factors, such as ambivalence toward pregnancy, can increase the risk of morning sickness.

What can be done to prevent the condition?
There is no known way to prevent morning sickness.

How is the condition diagnosed?
Morning sickness is diagnosed on the basis of the symptoms. Urinalysis may be done, as well as blood tests to check for dehydration.

What are the long-term effects of the condition?
Possible long-term effects of morning sickness are weight loss, dehydration, imbalances in fluids and electrolytes, and starvation. If these are not treated, they can rarely lead to liver, kidney, heart, and brain damage to the mother and the foetus.

Severe morning sickness can strain a marriage, and hinder job performance. Most women feel better after the start of the second trimester and the pregnancy can continue with no further problems.

What are the risks to others?
There are risks to the foetus if morning sickness is severe enough. Severe morning sickness if persistent, hyperemesis gravidarum, can cause low birth weight and foetal growth retardation. The volume of fluid in the blood vessels may be decreased. The blood flow to the placenta and foetus is also decreased, and less oxygen and nutrients are be delivered to the baby. Low birth weight is often linked with reduced overall health of the baby.

What are the treatments for the condition?
The treatment of morning sickness depends on how severe it is. Conservative treatment is tried first. This includes adjustments to the diet and lifestyle. The mother is advised to avoid things that produce the symptoms, such as certain foods and smells. She should eat smaller, more frequent meals. Dry crackers or toast, tea, cold liquids, and carbonated drinks may help lessen morning sickness. Eating before getting out of bed may help prevent the nausea.

Medications to prevent nausea are sometimes used.

If the morning sickness is quite severe, it is called hyperemesis gravidarum. Intravenous fluids may be needed to correct fluid and electrolyte imbalances and dehydration. Severe morning sickness may require hospitalisation.

Education and emotional support are very helpful for the woman with morning sickness. A nutritionist who routinely works with pregnant woman may help. A social worker may be asked to get involved with the family. A woman with morning sickness needs reassurance that it is okay to change her schedule to allow for more rest. Anti-nausea medications may be needed to keep the woman from vomiting.

What are the side effects of the treatments?
There are a number of medications used for nausea in pregnancy where the benefits outweigh the minimal risks.

What happens after treatment for the condition?
Morning sickness usually gets better by the beginning of the second trimester (12 weeks).

How is the condition monitored?
Morning sickness is monitored at antenatal visits. These visits are an important aspect of all pregnancies.

Author: Gail Hendrickson, RN, BS
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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