Nausea and vomiting in pregnancy is mistakenly known as “morning” sickness. Mistakenly, because it doesn’t occur only in the morning. One Canadian study reported 80% of its sample of pregnant women experienced nausea that lasted all day, compared to only 1.8% who reported it occurring just in the morning. However, half of pregnant women in a British study did vomit in the morning, between 6am and 12pm.

The exact cause of the nausea and vomiting in pregnancy is unknown, although various factors and hypotheses have been suggested.

The most popular evolutionary hypothesis linked to nutrition seems to be that nausea and vomiting may have protected pregnant mothers and their unborn children against potentially harmful substances in food. Imagine you’re a pregnant, hairy woman who feels too sick to try that new, delicious-looking plant that has just started to grow on your cavestep.

Negative effects of pregnancy nausea on mum can includestress, anxiety and depression, an inability to work, malnutrition, dehydration, contribution to constipation, decreased quality of life and irritability, increased sleep disturbances and lowered mood.

What should you eat?

It can be hard to eat a balanced diet when you are suffering from nausea and vomiting. You may only feel like oranges, hot chips, lemonade, ice blocks and pizza.

It’s best not to worry too much about this in the short term (beginning mid-pregnancy), as you can catch up with better nutrition when you start to feel more human. It’s better to eat anything than nothing at all.

It’s important to note some foods should be avoided during pregnancy. It’s also important to note more reflux-associated nausea and vomiting that may occur later in pregnancy comes with its own list of nutrition tips. These can be different to those for earlier nausea and vomiting.

The tips include eating smaller meals; not eating late at night; not consuming alcohol, fizzy drinks or other reflux-promoting foods and drinks such as spicy or fatty foods and peppermint; and chewing gum.

Even if you only manage to eat some chips and drink lemonade while you suffer from early nausea and vomiting, are there certain things you can eat or drink – or nutrition supplements you can take – that may help ease your symptoms?

There are lots ofreviews and guidelines on the nutritional management of nausea and vomiting in pregnancy. But there doesn’t seem to be enough high-quality evidence to be able to confidently recommend any particular nutrition strategy widely.

There are common nutrition practices that may help and are widely used by women all over the world. Many have good anecdotal support but few have been investigated in scientific studies. That doesn’t mean they don’t work, though. Some of the common tips in the literature are:

• identify and avoid things that you find triggering
• avoid having an empty stomach
• keep some bland food like dry crackers by your bedside and have a few before getting up in the morning
• eat small amounts of food often and avoid large meals
• eat at times when you feel less nauseous (although you will likely have to force yourself at times to eat when you feel nauseous, as it may be the only thing that makes you feel better)
• avoid spicy and fatty foods, which can irritate the stomach and/or decrease the rate of stomach emptying
• avoid foods with strong smells (your sense of smell can become very heightened while pregnant and some smells may make you feel sick – including food smells)
• cold or frozen drinks or foods are often better tolerated
• have foods and fluids at separate times to decrease the volume in your stomach
• drink small amounts of fluid often, but try to have about two litres daily (especially if you’re vomiting)
• herbal teas (such as ginger) may help.

There has been more research into certain nutrition supplements. These also may improve nausea and vomiting symptoms – although the evidence is not yet robust enough for wide application:

• Ginger as syrup or capsules up to 250mg four times a day may help, appears to be safe and is recommended in America. However, it is not recommended in Australian Clinical Practice Guidelines.

• Vitamin B6 (pyridoxine) may improve nausea at a dose of 10-25mg every eight hours, or 25-50mg orally up to four times daily (200mg per day has been shown to be safe). Again, this is not recommended in Australian Clinical Practice Guidelines.

• Discontinuation of iron or multivitamin supplements is recommended in the Australian Clinical Practice Guidelines, as these may contribute to nausea.

If your nausea and vomiting are more severe, then the above strategies may do absolutely nothing for you. You may need to move onto pharmaceutical and other management options. These include the anti-nausea drug ondansetron, which evidence suggests is unlikely to have any severe adverse effects on baby – unlike thalidomide in times gone by.

Even though almost three-quarters of Australian women may use at least one kind of “complementary therapy” during pregnancy, such as acupressure travel bands or acupuncture, the evidence for most is inconclusive.

Dr Reynolds is a registered nutritionist with the Nutrition Society of Australia and the owner of The Real Bok Choy www.therealbokchoy.com, a nutrition and lifestyle consultancy.