Morning sickness

Page last reviewed: 13/07/2011

Nausea and vomiting in pregnancy (NVP) is an unwelcome but perfectly normal part of pregnancy. It does not put your baby at any increased risk.

Although it is commonly called morning sickness, NVP can occur at any time of the day.

How common is NVP?

During early pregnancy, nausea, vomiting and tiredness are common symptoms. Around half of all pregnant women experience nausea and vomiting, and around 3 in 10 women experience nausea without vomiting.


NVP usually starts to get better after the first three months of pregnancy. However, some women continue to experience NVP for a longer period. About 1 woman in 10 continues to feel sick after week 20 of their pregnancy.

NVP is sometimes considered to be a minor inconvenience of pregnancy, but it can have a significant, adverse effect on an expectant mother's day-to-day activities and quality of life.

NVP can often be treated by making dietary changes and taking plenty of rest. The support of family and friends can also make NVP more manageable.

Nausea is when you feel like you're going to be sick.

Page last reviewed: 13/07/2011

For most women, the symptoms of nausea and vomiting in pregnancy (NVP) usually begin before the ninth week of pregnancy, around six weeks after their last period.

The symptoms of NVP should improve as your pregnancy progresses. In about 90% of cases, symptoms disappear by the third month of pregnancy.

When to seek medical advice

Sometimes, symptoms of nausea and vomiting can be caused by a more serious, underlying health condition such as:

  • urinary tract infection a common infection that can affect the kidneys, bladder, urethra and the ureters (the tubes that run from the kidneys to the bladder)
  • appendicitis a common condition that causes inflammation (swelling) of the appendix
  • pancreatitis an uncommon but potentially serious condition that causes inflammation (swelling) of the pancreas.

Contact your GP or midwife immediately if you:

  • have very dark-coloured urine or do not pass urine for more than eight hours
  • have abdominal (tummy) pain
  • have a high temperature (fever) of 38C (100.4F) or above
  • feel severely weak, dizzy or faint when standing up
  • vomit blood
  • have a racing heart rate
  • have repeated episodes of vomiting
  • are unable to keep food or fluids down for 24 hours
Dehydration is an excessive loss of fluids and minerals from the body.
Nausea is when you feel like you are going to be sick.
Vomiting is when you bring up the contents of your stomach through your mouth.

Page last reviewed: 13/07/2011

The exact cause of nausea and vomiting in pregnancy (NVP) is unknown. However, a number of different causes have been suggested, including:

  • increased oestrogen levels
  • increased human chorionic gonadotrophin (hCG) levels
  • nutritional deficiency
  • gastric problems                
  • evolutionary adaptation
  • psychological influences

These are explained in more detail below.


Changes in levels of the female sex hormone oestrogen during the early stages of pregnancy may cause short-term nausea and vomiting.

During pregnancy, oestrogen levels begin to rise. They tend to be at their highest during the first three months when the symptoms of NVP are at their worst.

Rising levels of oestrogen can heighten your sense of smell, which may explain why certain smells can trigger the onset of symptoms.

HCG levels

After conception (when the sperm fertilises the egg), the body begins to produce a hormone called human chorionic gonadotrophin (hCG). It is thought that a rise in the level of hCG may cause nausea and vomiting during pregnancy.

Nutritional deficiency

A lack of vitamin B6 in the diet is thought to be another possible cause of NVP. Foods that contain vitamin B6 include:

  • whole cereals (oatmeal and wheat germ)
  • bread
  • cod
  • soya beans
  • milk
  • potatoes
  • peanuts

It is thought that a lack of vitamin B6 may cause hyperemesis gravidarum, an uncommon but severe form of nausea and vomiting that some women experience during pregnancy.

See Morning sickness - complications for more information about hyperemesis gravidarum.

Gastric problems

During pregnancy, levels of progesterone are increased. Progesterone is a hormone that helps prepare the womb for pregnancy and protects the womb lining.

As progesterone production increases, the movement in the small intestine, oesophagus (gullet) and stomach reduces, causing NVP. The reduction in movement occurs as a result of the muscle walls relaxing.

Evolutionary adaptation

Evolutionary adaptation is a change that occurs in an organism in order to make it better adapted to its environment.

Some scientists believe that NVP may be the result of an evolutionary adaptation that has occurred to protect women and their baby from food poisoning.

Pregnant women with NVP often do not feel like eating foods that can potentially become contaminated, such as meat, poultry and eggs. Instead, foods with a low risk of contamination, such as bread and crackers, tend to be preferred.

Psychological influences

Although it is not a very popular theory, it has been suggested that NVP may be the result of the body responding to stress or negative feelings towards the pregnancy. Conversely, it has also been suggested that these psychological symptoms may possibly be the result of NVP.

Risk factors

A number of different factors are associated with an increased risk of developing NVP. These include:

  • previous pregnancy with nausea and vomiting
  • female foetus
  • family history of NVP
  • history of motion sickness
  • history of nausea while using contraceptives that contain oestrogen
  • young maternal age
  • obesity
  • stress
  • multiple pregnancies, such as twins or triplets
  • first pregnancy

An enlarged placenta is also a known risk factor for NVP. The placenta is the organ that attaches the mother to her unborn baby and provides the baby with food and oxygen.

The placenta can become enlarged in multiple pregnancies, such as twins or triplets, or during a molar pregnancy, where the fertilisation of the egg goes wrong and leads to an abnormal growth of cells inside the womb.

Page last reviewed: 13/07/2011

Nausea and vomiting in pregnancy (NVP) can usually be diagnosed on the basis of the symptoms alone.

Urine test

If you experience very severe vomiting, your GP may recommend that you have a urine test.

This checks for the presence of ketones (the end product of the breakdown of fatty acids). Ketones are often found in urine if the body is forced to break down fat, rather than glucose, for energy.

Ketones are toxic (poisonous), acidic chemicals such as:

  • acetone
  • acetoacetate
  • beta-hydroxybutyrate

If high ketone levels are found in your urine, it may be a sign that the severe vomiting is causing you to become malnourished. If this is the case, you will require extra nutrients and possibly medicine to help prevent further vomiting.

Page last reviewed: 13/07/2011

If you have nausea and vomiting in pregnancy (NVP), your GP or midwife will initially recommend that you try a number of dietary and lifestyle changes to help reduce your symptoms.

In severe cases of NVP, medication may be recommended. There are also a number of other possible treatments that may prove useful.

Typical treatments for NVP are described below.

Dietary and lifestyle changes

Dietary and lifestyle changes that may help reduce your symptoms of NVP include:

  • getting plenty of rest because tiredness can make nausea worse
  • drinking little and often, rather than in large amounts, because this may help prevent vomiting.
  • eating small, frequent meals that are high in carbohydrate and low in fat (savoury foods, such as toast, crackers and crisp-bread, are usually better tolerated than sweet or spicy foods)
  • eating cold meals rather than hot ones because they do not give off the smell that hot meals often do, which may provoke nausea
  • eating plain biscuits before getting up
  • avoiding foods or smells that trigger your symptoms
  • avoiding drinks that are cold, tart (sharp) or sweet
  • wearing comfortable clothes without tight waistbands, which can sometimes make you feel uncomfortable


If your symptoms of nausea and vomiting in pregnancy (NVP) are severe and do not improve after you make changes to your diet and lifestyle, your GP may recommend a short-term course of an anti-sickness medicine that is safe to use in pregnancy.
This type of medicine is called an anti-emetic and helps to prevent vomiting.

Possible side effects of anti-emetics include:

  • constipation
  • headaches
  • flushing of the skin (warm sensation on the skin)
  • tiredness (fatigue)
  • feelings of weakness
  • indigestion
  • insomnia
  • muscle twitching 


There is some evidence that taking certain types of antihistamines (medicines that are often used to treat allergies) may help reduce the symptoms of nausea.Antihistamines may be used in combination with Vitamin B6.

Antihistamines have not been found to be harmful to the unborn baby,although they may make you drowsy

Other treatments


There is some evidence that ginger supplements may help reduce the symptoms of nausea and vomiting in some pregnant women.

To date, there have not been any reports of adverse effects being caused by taking ginger during pregnancy. However, ginger products are unlicensed in the UK, so buy them from a reputable source, such as a pharmacy or supermarket. Check with your pharmacist before you use ginger supplements.


There are conflicting reports on the effectiveness of a form of accupunture,known as accupressure ,for improving the symptoms of nausea and vomiting of pregnancy.

Acupressure involves wearing a special band on your forearm. Some researchers have suggested that putting pressure on certain parts of the body may cause the brain to release painkilling chemicals.

There have been no reports of any serious adverse effects being caused by using acupressure during pregnancy, although some women have experienced numbness, pain and swelling in their hands

Over-the-counter (OTC) remedies are not recommended during pregnancy as further research is required into how safe they are and what effects they may have.

Antihistamine medicine counteracts the action of histamine (a chemical released during an allergic reaction).
Dehydration is an excessive loss of fluids and minerals from the body.
A drip is used to pass fluid or blood into your bloodstream, through a plastic tube and needle that goes into one of your arteries or veins.
Intravenous (IV) means the injection of blood, drugs or fluids into the bloodstream through a vein.
Veins are blood vessels that carry blood from the rest of the body back to the heart.
Vomiting is when you bring up the contents of your stomach through your mouth.

Page last reviewed: 13/07/2011

Hyperemesis gravidarum

Hyperemesis gravidarum is an uncommon but severe form of nausea and vomiting in pregnancy (NVP). It affects between 1 in 100 and 1 in 200 women, although estimates vary depending on how the condition is defined.

Symptoms of hyperemesis gravidarum include:

  • prolonged and severe nausea and vomiting
  • dehydration 
  • ketosis - a serious condition that is caused by a raised number of ketones in the blood; ketones are toxic (poisonous) acidic chemicals 
  • body weight loss 
  • low blood pressure (hypotension) when standing up

In addition, the symptoms can have a significant effect on your life and may lead to further complications, such as depression.

The symptoms of hyperemesis gravidarum are usually so severe that it is impossible to keep any fluids down. Excessive vomiting can cause dehydration and weight loss.

If your symptoms of nausea and vomiting are so severe that you are unable to tolerate fluids, seek urgent medical advice as soon as possible.

Treating hyperemesis gravidarum

Hyperemesis gravidarum needs specialist treatment. You may be admitted to hospital if you are losing too much fluid. This is so that your condition can be assessed and appropriate treatment given, such as increasing your fluid levels and treating the ketosis.

Hyperemesis gravidarum is unlikely to cause harm to your baby. However, if it causes weight loss during pregnancy, there is an increased risk that your baby may be born with a low birth weight.

Deep vein thrombosis

Due to the dehydration that is caused by hyperemesis gravidarum, there is also an increased risk of deep vein thrombosis occurring. Deep vein thrombosis (DVT) is a blood clot in one of the deep veins in the body.

Vomiting is when you bring up the contents of your stomach through your mouth.

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

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