• Introduction
• Symptoms
• Causes
• Diagnosis
• Treatment
• Complications
• Selected links
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Introduction

Nausea and vomiting in pregnancy (NVP) is an unwelcome but perfectly normal part of pregnancy and 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?

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

Outlook

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 affect on your day-to-day activities and quality of life.

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

Symptoms

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 urgent medical advice

Sometimes, symptoms of nausea and vomiting may 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, midwife, or call NHS Direct Wales on 0845 46 47 to speak to a nurse if you:

• have very dark coloured urine or you 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 down food or fluids for 24 hours

Causes

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.

Oestrogen

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 rise and tend to be at their highest in the first three months, when the symptoms of NVP are at their worst.

Rising levels of oestrogen may 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 is an evolutionary adaptation that has occurred in order 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 preferring foods which have a low risk of contamination, such as bread, or crackers.

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.

Diagnosis

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

Urine test

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

This is to check 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 levels of ketones 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.  

Treatment

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

Anti-emetics

If changing your diet and lifestyle does not work, and your symptoms of nausea and vomiting are severe, your GP may recommend a short-term course of a suitable anti-sickness medicine which is safe to use in pregnancy.

This type of medicine is called an anti-emetic and it 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   

Antihistamines

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 do not have an associated increased risk of harming your unborn baby, but they make you drowsy. See your GP if you would like to consider this form of treatment.

Other treatments

Ginger

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

And, to date, there have been no reports of any adverse effects caused by taking ginger during pregnancy. However, in the UK, ginger products are unlicensed, so it is important that you buy them from a reputable source, such as a pharmacy or supermarket. Check with your pharmacist before you use ginger supplements.

Acupressure

There is some limited evidence that a form of acupuncture, known as acupressure, may help to improve the symptoms of nausea and vomiting in some women.

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 be 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.

Vitamin B6

Further evidence is required to establish the benefits of using vitamin B6 supplements during pregnancy.

Although vitamin B6 appears to be effective at reducing the symptoms of NVP, there is limited evidence regarding the strength (toxicity) of the vitamin, its effects and how safe it is to take during pregnancy.

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.

Complications

Hyperemesis gravidarum

Hyperemesis gravidarum is a rare, but severe form of nausea and vomiting in pregnancy (NVP). It affects around 1 in 200 women.

Symptoms of hyperemesis gravidarum include:

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

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.

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

Your GP may recommend that you be admitted to hospital if you are losing too much fluid.  This is so that your condition can be assessed and the appropriate treatment given.

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.

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.

See the topic about Deep vein thrombosis for more information about this potentially serious condition.

Selected links

NHS Direct Wales Topics

Pregnancy

Antenatal health