- Risk factors
- Cause of morning sickness
During pregnancy many women experience symptoms of nausea (70-85%) and vomiting (50%). Often referred to as ‘morning sickness’ nausea and vomiting during pregnancy can occur at any time of the day, especially at times when the pregnant woman is tired or hungry. For most, the symptoms are mild and temporary and in 90% of women nausea and vomiting stops of its own accord by the 16th week of pregnancy.
If nausea and vomiting begins later in pregnancy it may be caused by a condition other than pregnancy. Causes of nausea and/or vomiting which commences after the 16th week of pregnancy include urinary tract infection and food poisoning. Introduction to nausea and vomiting in pregnancy
Some women are more likely to experience morning sickness than other women. These include women:
- With a history of motion sickness;
- With a history of migraine headaches;
- With a family history or previous pregnancy with the condition;
- With a history of nausea with use of combined oral contraceptives;
- With a poor diet, for women who had a high daily total fat intake prior to pregnancy- these women can often manage morning sickness by modifying their diet;
- Carrying a female foetus;
- Who are young;
- Who are pregnant for the first time;
- Who are obese; and
- Who experience stress.
The risk of developing pregnancy induced nausea and vomiting is reduced in:
- Smokers, however women should not smoke during pregnancy to reduce their symptoms of morning sickness. The risks of smoking to mother and baby far outweigh the benefits of reduced nausea and vomiting. They include prematurity, intrauterine growth restriction (IUGR), sudden infant death syndrome (SIDS), stillbirth and spontaneous abortion.
- Those taking multivitamin supplements early in the pregnancy, specifically prior to the 6th week of pregnancy.
The cause of pregnancy induced nausea and vomiting is not well understood, however most health professionals agree that it is stimulated by the placenta. The placenta is the organ that protects and nourishes the foetus during pregnancy and it produces a hormone called human chorionic gonadotrophin (hCG) which is not produced by non-pregnant women.
The production of hCG by the placenta is thought to cause morning sickness for a number of reasons. Firstly, morning sickness usually begins at the time the placenta begins producing hCG. Secondly, morning sickness is more common in pregnant women who have higher concentrations of hCG in their bodies, including women with multiple pregnancies (twins or greater) and those with molar pregnancy.
The hormone oestrogen is also thought to play a role in the development of morning sickness because oestrogens in combined oral contraceptives can cause nausea and vomiting. The reduced likelihood of morning sickness in smokers may also result from lower levels of oestrogen, as smoking reduces oestrogen levels.
Although morning sickness brings discomfort, there is no evidence that it harms the developing foetus. On the contrary, evidence suggests that women who experience morning sickness are less likely to have a miscarriage and/or stillbirth. However, morning sickness can significantly affect a woman’s psychological health and quality of life. It is therefore important to seek professional advice about how to reduce nausea and vomiting during pregnancy. Nutritional management (link to below) is one strategy for relieving these symptoms.
Severe nausea and vomiting during pregnancy, a condition known as hyperemesis gravidarum affects 0.5% to 2% of pregnancies. The condition is characterised by persistent vomiting, dehydration, ketonuria (presence of ketone in the urine), electrolyte disturbance (imbalances in the content of body fluids and tissues) and weight loss greater than 5% of total body weight.
Hyperemesis gravidarum is the most common reason for presentation to hospital in early pregnancy and can have serious effects on foetal development. It is also important for doctors to exclude other causes (e.g. food poisoning) when women present with severe nausea and vomiting during pregnancy.
Hyperemesis gravidarum can occur as a normal complication of pregnancy but is also associated with:
- Hydatiform mole
- Multiple pregnancy
- Urinary infection
Severe nausea and vomiting can have negative effects on the woman’s quality of life. Up to 60% of women with hyperemesis gravidarum develop secondary depression and some may choose to terminate their pregnancy because they are unable to cope with the nausea and vomiting it causes. Many women who experience hyperemesis gravidarum describe feelings of:
- Frustration at being unable to complete activities of daily living and role function;
- Delay in maternal role attainment (feeling like a mother);
- Concern for the effects on the unborn child;
- Lowered self-efficacy; and
- Alterations in relationships with family, partners, and friends.
A doctor will recommend different strategies for dealing with morning sickness, depending on the severity of the condition. There is no definite cure for morning sickness because its causes are varied and not well understood.
Mild and moderate cases of morning sickness usually resolve without intervention by the 16th week of pregnancy. However, women who have concerns about mild-moderate morning sickness in the first trimester of pregnancy should discuss their condition with a health professional, if only to obtain information about the condition and reassurance that their morning sickness is normal and will not have negative affects on the development of their foetus.
Women with moderate morning sickness may also be given medication. Vitamin B6 (also called pyridoxine) tablets are the most common medication used to relieve morning sickness. If vitamin B6 therapy does not relieve morning sickness, the doctor may prescribe a medicine called metoclopramide.
Dietary interventions may also be effective in mild-moderate cases of morning sickness.
Dietary interventions or nutritional management strategies which may reduce morning sickness in pregnant women include:
- Drink plenty of fluids to prevent dehydration. Women who are unable to eat should attempt to drink fluids with higher nutritional contents, including fruit juice, soup and soft drink;
- At times when nausea and vomiting is so severe that it prevents a woman eating she should drink fluids until it is possible to eat again;
- Drink fluids (preferably water or other clear fluids such as lemonade) frequently;
- Try sucking frozen drinks or ice blocks;
- Avoid large drinks by drinking smaller quantities of fluid more frequently;11
- Drink before and after meals, but avoid drinking whilst eating;
- Avoid caffeine containing drinks;
- Avoid fluids which are bitter or sweet.
- Eat small but frequent meals;
- Eat slowly and ensure food is properly chewed before swallowing;
- Don’t skip meals as this can make nausea worse;
- Eat foods which are high in carbohydrates (e.g. rice, cereal, starchy vegetables like potatoes) and low in fat;
- Eat at least some low-fat sources of protein, for example lean meat;
- Eat plain, savoury foods such as toast and crackers, rather than sweet or spicy foods;
- Eat cold meals as these typically have less offensive smells than hot meals. However, be sure to avoid foods which present a risk for listeriosis, including deli meats and left-overs which are more than 24 hours old;
- Eat something bland like a plain cracker 20 minutes before rising from bed in the morning;9
- Eat a snack containing both protein and carbohydrates (e.g. cheese and crackers) before going to bed;
- Avoid foods which are smelly or are known to cause nausea. Where possible, pregnant women with morning sickness should have someone cook meals for them so that they can avoid the smell of food cooking.
Consuming large quantities of ginger can relieve nausea during pregnancy. However, more research is needed to determine whether or not it is safe for pregnant women to consume large amounts of ginger.
Severe and prolonged vomiting during pregnancy can result in nutritional losses, dehydration and maternal malnutrition. Hyperemesis gravidarum may negatively influence foetal development and the most likely risks are intrauterine growth retardation and the baby being born at a low birth weight.
In severe cases of morning sickness it is very important that a doctor ensures the nausea and vomiting are caused by pregnancy, and not another condition (e.g. food poisoning). A doctor will typically need to ask questions about the pregnancy, the woman’s diet and other symptoms she experiences. Blood and urine tests or an ultrasound may also sometimes be necessary.
Women with severe nausea and vomiting will typically require medication to relieve their condition. The most commonly prescribed medications are:
- Prochlorperazine (Stemetil)
- Metoclopramide (Maxolon)
- Pyridoxine (Vitamin B6)
Other medications which may be prescribed include:
- Medications which restore fluid & electrolyte balance;
- Folic acid and multivitamins.
Nutritional interventions which help women to consume more food may also be required to ensure women with severe vomiting do not become malnourished.
Women with severe nausea and vomiting may require additional nutrition to account for nutritional losses associated with vomiting. However, as women with morning sickness are ill and unlikely to feel like eating, maintaining a healthy, balanced diet is likely to be challenging. Individuals who lose weight or have difficulty maintaining a healthy diet should seek nutritional advice from a health professional.
For more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see Pregnancy.
For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.
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- Morning sickness [online]. London, UK: National Health Services; 2008 [cited 23 January 2010]. Available from: URL link
- Managing morning sickness [online]. Brisbane, QLD: Queensland Government Department of Health; 2009. [cited 15 May 2010]. Available from: URL link
- Healthy eating at various lifestages: Pregnant women [online]. Canberra, ACT: Australian Government Department of Health and Ageing; 19 October 2009 [cited 15 May 2010]. Available from: URL link
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