Summary

  • Around half to two-thirds of all pregnant women will experience morning sickness.
  • Possible causes include high levels of hormones, blood pressure fluctuations and changes in carbohydrate metabolism.
  • Severe morning sickness, called hyperemesis gravidarum, may require hospitalisation.
  • Symptoms of morning sickness may be relieved by eating a few dry crackers before you get up in the morning, avoiding foods and smells that make you nauseous, drinking plenty of fluids and choosing high-carbohydrate and high-protein foods.
Around half to two-thirds of all pregnant women will experience morning sickness to some degree, particularly in the first trimester. The symptoms include nausea and vomiting. Morning sickness is typically at its worst early in the day, hence its name, but it can strike at any point during the day or night.

For most women, morning sickness begins around the fourth week of pregnancy and resolves by the 12th to 14th week. However, one in five women endures morning sickness into their second trimester, and an unfortunate few experience nausea and vomiting for the entire duration of their pregnancy.

In most cases, morning sickness doesn’t harm the woman or the unborn child. However, severe morning sickness that includes weight loss and dehydration needs prompt medical attention.

Symptoms of morning sickness

Symptoms of morning sickness can include:
  • Nausea
  • Loss of appetite
  • Vomiting
  • Psychological effects, such as depression and anxiety.

The myth of hysteria and morning sickness

Unrelenting morning sickness can have a profound effect on your quality of life, preventing you from working, socialising and looking after your other children.

Pregnant women enduring morning sickness report higher levels of psychological stress, including anxiety and depression. This prompted the false belief that morning sickness is purely psychosomatic, which means that the woman’s fears and anxieties trigger her physical discomfort. However, there is no research to support these claims.

Possible causes of morning sickness

The cause of morning sickness remains a mystery, but it is thought a combination of physical and metabolic factors play a significant role, including:
  • High levels of hormones, including oestrogen
  • Fluctuations in blood pressure, particularly lowered blood pressure
  • Altered metabolism of carbohydrates
  • The enormous physical and chemical changes that pregnancy triggers.

Morning sickness and your baby

Some women are concerned that the action of vomiting may threaten their unborn baby. Vomiting and retching may strain the abdominal muscles and cause localised aching and soreness, but the physical mechanics of vomiting won’t harm the baby. The fetus is perfectly cushioned inside its sac of amniotic fluid.

Numerous studies have discovered that moderate morning sickness is associated with a reduced risk of miscarriage. However, prolonged vomiting (that leads to dehydration and weight loss) can deprive your child of proper nutrition and increase the risk of your baby being underweight at birth.

If you have nausea and vomiting that will not stop, contact your doctor or midwife.

Severe morning sickness (hyperemesis gravidarum)

Severe morning sickness is known as hyperemesis gravidarum (HG), and can affect around one in 1,000 pregnant women. The symptoms of HG include repeated vomiting, weight loss and dehydration. Treatment usually involves hospitalisation, and the administering of intravenous liquids and nutrition.

The possible complications of untreated hyperemesis gravidarum include:
  • Electrolyte imbalances
  • Extreme depression and anxiety
  • Malnourishment of the fetus
  • Excessive strain on vital organs, including the liver, heart, kidneys and brain.

Managing morning sickness

Suggestions for coping with morning sickness include:
  • Don’t take drugs of any kind, unless your doctor knows you are pregnant and has prescribed specific medications.
  • Eat a few dry crackers or plain sweet biscuits before getting out of bed in the morning.
  • Don’t eat anything that you suspect will make you nauseous. In general high-carbohydrate meals are well tolerated.
  • Eat small meals regularly, as an empty stomach tends to trigger nausea.
  • It may help to avoid cooking or preparing foods.
  • Drink as much as you can manage. Sometimes sips of flat lemonade, diluted fruit juice, cordial, weak tea, ginger tea, clear soup or beef extract drinks are helpful. If none of these are bearable, try sucking on ice cubes.
  • Vitamin B6 supplements can be useful, but doses above 200 mg per day can actually be harmful. Follow your doctor’s advice.
  • Consider acupressure or acupuncture on the wrist.
  • Wear loose clothes that don’t constrict your abdomen.
  • Moving around may aggravate morning sickness. Rest whenever possible.

Seeing your doctor about morning sickness

Always seek medical advice if your morning sickness is severe, if you have lost a lot of weight quickly, or if you feel depressed or anxious. Treatment options can include drugs that won’t harm your developing baby.

Where to get help

  • Your doctor
  • Maternal and child health nurse

Things to remember

  • Around half to two-thirds of all pregnant women will experience morning sickness.
  • Possible causes include high levels of hormones, blood pressure fluctuations and changes in carbohydrate metabolism.
  • Severe morning sickness, called hyperemesis gravidarum, may require hospitalisation.
  • Symptoms of morning sickness may be relieved by eating a few dry crackers before you get up in the morning, avoiding foods and smells that make you nauseous, drinking plenty of fluids and choosing high-carbohydrate and high-protein foods.
  • Nausea and vomiting in pregnancy (morning sickness), 2012, The Royal Women’s Hospital. More information here.
  • Chan RL, Olshan AF, Savitz DA, et al., 2010, ‘Severity and duration of nausea and vomiting symptoms in pregnancy and spontaneous abortion’, Human Reproduction, vol. 25, no. 11, pp. 2907–2912. More information here.

More information

Healthy pregnancy

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Keeping healthy during pregnancy

Health concerns during pregnancy

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Last updated: July 2013

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