Written by:

Dr Bonnie Ng

MBChB, BMedSci (Hons), MRCOG

MRC Clinical Research Fellow in Obstetrics and Gynaecology, ST4 Southampton

Nausea and vomiting in pregnancy

In this article:

  • How common is nausea and vomiting in pregnancy?
  • Why is it called morning sickness?
  • Why does it occur?
  • Should I be worried?
  • Diet and lifestyle tips
  • Treatment of morning sickness
  • Hyperemesis gravidarum
  • When to get help
  • Main Points

Nausea and vomiting in pregnancy

This article covers everything you need to know about the most common symptom of early pregnancy, how to get some relief and when to seek help.

How common is nausea and vomiting in pregnancy?

Nausea and vomiting is a common symptom in pregnancy, experienced by 50-90% of women. It usually starts before week 9 of pregnancy, and for most women subsides at some point between week 16 and week 20. However, for some, it can last for several more weeks or months and can even last throughout the pregnancy.

Why is it called morning sickness?

Nausea and vomiting in pregnancy is commonly referred to as “morning sickness” as it is more likely to occur early in the day. However, it can affect you at any time of the day or night, and in some cases can last all day long. Therefore the term morning sickness can be misleading for the general public.

Why does it occur?

Although the cause of nausea and vomiting in pregnancy is uncertain, there are several possible reasons why it may occur.

Hormones

Human chorionic gonadotrophin (hCG), a hormone that is produced initially by the developing embryo and then later by the placenta, is thought to stimulate nausea and vomiting in pregnancy. HCG levels rise quickly during the first few weeks of pregnancy and this is typically when nausea starts. Women with higher hCG levels, for example in twin or triplet pregnancies, are more likely to get nausea and vomiting.

The other hormone thought to contribute is oestrogen; nausea and vomiting is more common when oestrogen levels are increased (they can be as much as 100 times higher during pregnancy).

Evolutionary benefit

Nausea and vomiting in pregnancy is thought to be an evolutionary adaptation as it prevents the woman from eating potentially harmful or even poisonous foods.

Delayed gastric emptying

In pregnancy, increased levels of the hormone progesterone mean that “smooth muscle” in the body relaxes more. Examples of this type of muscle include the sphincter between the oesophagus and the stomach, the stomach itself and also the intestines. Relaxation of the stomach sphincter means that food and stomach acid is more likely to be regurgitated back into the oesophagus. This can lead to heartburn or nausea and vomiting.

When the stomach and intestines are relaxed, the stomach empties more slowly and there is slower passage of food through the bowels. This can cause a “back-up effect” which contributes to nausea and vomiting. It also contributes to other pregnancy symptoms such as bloating, wind and constipation.

Should I be worried?

Mild nausea and vomiting in pregnancy does not harm the baby. Some studies have even shown that women who get morning sickness are less likely to have a miscarriage (this does not mean women who do not have morning sickness are more likely to miscarry). Some women may find that it is hard to put on weight and may even lose a little weight in the first trimester — this is usually normal and nothing to worry about.

Nausea and vomiting can, however, affect your life and ability to go about daily activities or go to work. It can also leave you feeling exhausted and in a low mood. It is important that you look after yourself during this time to prevent your symptoms from getting worse. If you feel like you aren’t coping, seek medical advice.

If nausea and vomiting is severe or long-standing, resulting in loss of a significant amount of weight or an inability to gain weight into the second trimester, this can affect your baby’s growth.

Diet and lifestyle tips

There are some simple diet and lifestyle changes you may want to consider:

  • Get plenty of rest.
  • Take prenatal vitamins to ensure you are still getting adequate vitamins and minerals. It may be best to take them before bed with a light snack to reduce the chances of them being brought back up.
  • Eat little and often — eating smaller meals, e.g. five or six “mini-meals” ensures that your stomach is never empty. Nausea can be made worse from overeating or excessive hunger.
  • Drink plenty of fluids such as water — it is better to sip little and often to prevent vomiting and to ensure you stay hydrated.
  • Ginger can help reduce nausea and vomiting symptoms — try ginger candies or capsules, or use fresh ginger to make tea.
  • Aromatherapy — smelling fresh mint, lemon, orange or ginger as these scents may help ease symptoms.
  • Try taking bland foods that have a low-fat content and are easy to digest — e.g. rice, pasta, dry crackers and toast.
  • Try small pieces of fruit — these can also increase your fluid intake.
  • It may be helpful to have a food diary to identify the foods that don’t agree with you, or foods that you can eat and keep down. This will help you to adjust your diet to reduce your symptoms.
  • Keep physically and mentally active.
  • Protect your teeth — frequent vomiting results in the acidic contents of your stomach being brought up. This can wear away the enamel on your teeth. To help protect your teeth, after you have vomited you should rinse your mouth with water.

Treatment of morning sickness

Unfortunately, there is no quick fix for nausea and vomiting in pregnancy and every woman’s experience in pregnancy is different. The goal is to try to find foods and drinks that you can keep down. This will help you get on with life while still getting the nutrition you need for your baby’s development. If simple lifestyle and diet changes don’t work for you or you are having more severe symptoms, your midwife or doctor may recommend anti-sickness medications (anti-emetics). Usually, this will be in the form of tablets or medications that you place under your tongue (sublingual) or between your gums and the inner lining of the mouth cheek (buccal). Some women may need a combination of medications to get relief. These medications are usually a short-term measure to help with your symptoms.

Acupuncture, or the application of pressure on specific points of the body may control symptoms, although there are no large scale trials that prove its effectiveness. Acupuncture is also likely to be an expensive way of treating morning sickness. Elastic acupuncture wristbands are an easier and less expensive option and are available from most pharmacies. These have a plastic button that presses on the acupuncture point on the wrist that is thought to relieve the nausea.

Hyperemesis gravidarum

Hyperemesis gravidarum (HG) is a term used for the most severe form of nausea and vomiting in pregnancy and occurs in up to 3% of pregnancies. It is diagnosed when a woman has lost 5% of her pre-pregnancy weight and has problems related to dehydration. Some cases of HG require inpatient treatment in a hospital to stop vomiting and to restore body fluids.
HG can be serious and may require urgent medical input. This is because women with HG may experience electrolyte (or salt) imbalances, vitamin deficiencies and other symptoms of starvation that can lead to increased risk of blood clots and brain dysfunction.

When to get help

If you are experiencing nausea and vomiting in pregnancy, remember that you are not alone. Accept help from family and friends, who may be able to take over household chores or provide childcare so you can get as much rest as possible.
You should contact you midwife or GP if you are vomiting in pregnancy and:

  • Have very dark coloured urine, have difficulty passing urine, or have not passed urine in more than 8 hours.
  • Are unable to keep food/fluids down for 24 hours.
  • Feel weak, dizzy or faint when standing up.
  • Have tummy pain.
  • Have pain or blood when you pass urine.
  • Have lost weight.

If out of hours and you experience any of the above, it is advisable that you call 111 for medical advice. You may be advised to attend your local urgent care center or A&E for assessment. For more, you can join our forum and see how others are coping, or read one mum’s perspective on hyperemesis gravidarum.

Main Points

  • Nausea and vomiting in pregnancy is experienced by 50-90% of women. It usually starts before week 9, and for most women subsides at some point between week 16 and week 20. However, for some, it can last for the duration of the pregnancy.
  • Although it is commonly called morning sickness, it can occur at any time of the day or night.
  • Nausea and vomiting in pregnancy is caused by various factors, including a hormone called human chorionic gonadotropin (hCG) that is produced initially by the developing embryo and then later by the placenta.
  • Nausea and vomiting in pregnancy may also be attributable to increased levels of hormone progesterone, which then causes relaxation of the stomach sphincter and more frequent regurgitation.
  • Mild nausea and vomiting in pregnancy is not harmful to your baby. However, if it is severe or long-standing and results in significant weight loss or an inability to gain weight into the second trimester, this can affect your baby’s growth.
  • There are some dietary and lifestyle changes you can make that may help to reduce nausea and vomiting in pregnancy.
  • There is no quick fix for nausea and vomiting in pregnancy. However, your midwife or doctor may recommend anti-sickness medications (anti-emetics) for short-term relief.
  • Hyperemesis gravidarum (HG) is the most severe form of nausea and vomiting in pregnancy and occurs in up to 3% of pregnancies. It is diagnosed when a woman has lost 5% of her pre-pregnancy weight and has problems related to dehydration.
  • You should contact you midwife or GP if you are vomiting in pregnancy and have very dark coloured urine, have difficulty passing urine, or have not passed urine in more than 8 hours; are unable to keep food/fluids down for 24 hours; feel weak, dizzy or faint when standing up; have tummy pain; have pain or blood when you pass urine; or have lost weight.

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Important – If you or your child are unwell you should seek medical advice from a professional – contact your GP or visit an A&E department in an emergency. While My BabyManual strives to provide dependable and trusted information on pregnancy and childcare 24/7 via our website pages, we cannot provide individual answers to specific healthcare questions.