Facts Behind Common Advice

You may read a lot of advice about what you should avoid during pregnancy, but do you know why? Below we have detailed why and how these pose a risk to you or your baby so you are able to make an informed choice.


Advice:  If you smoke, quit smoking as soon as you discover you’re pregnant.

Why?   When you smoke, your baby shares chemicals from the smoke you breathe. It also means that the dangerous chemicals in other people’s smoke – secondhand smoke – can affect your baby.

When you smoke, or inhale other people’s secondhand smoke, the smoke goes into your lungs. Chemicals from the smoke, such as carbon monoxide, are then absorbed into your bloodstream replacing the oxygen and restricting the supply to your baby. Oxygen is essential for your baby’s growth and development and when oxygen is restricted their tiny hearts must beat harder. Smoking during pregnancy can also damage your baby’s airways before it is born.

If you smoke during pregnancy your child may develop smaller airways, making them more vulnerable to breathing problems such as asthma.

Research has shown airflow through the breathing tubes is on average 20% lower in babies born to mothers who smoke. On average, smokers have more complications during pregnancy and labour which can include bleeding during pregnancy and placental abruption.

Women who stop smoking during the first three months of pregnancy have a lower rate of placental abruption and a lower rate of placenta praevia compared to continuing smokers so quit smoking as soon as possible.

Smokers are five times more likely to develop eclampsia which is a major cause of maternal mortality in the UK and smoking can cause a greater risk of miscarriage and stillbirth.
Your baby is more likely to be born prematurely and with a low birth weight if you smoke. Your baby is more likely to have extra problems in keeping warm and is also more prone to infection during and after labour.

After the birth your baby may cry more and be harder to settle. They are also more at risk of getting infections such as inflammation of the middle ear in childhood  and of getting asthma and other chest infections in young children.

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Foods to avoid

The Advice:  Don’t eat mould-ripened soft cheese, such as brie, camembert and chevre (a type of goats’ cheese) and others with a similar rind. You should also avoid soft blue-veined cheeses such as Danish blue or gorgonzola. Avoid all types of pate and raw or undercooked eggs.

Why? Soft cheeses are more likely to grow bacteria such as listeria, which can harm your unborn baby. Even if these cheeses are pasteurised, they still aren’t safe to eat. That’s because they are more moist and less acidic than other cheeses. It’s this moistness and acidity which provide the perfect environment for listeria bacteria to grow. However, though the risk of listeria contamination in hard, mould-ripened cheeses is very low, it can’t be ruled out. You may find it easier, and more reassuring, not to eat any blue cheeses, unless they’re cooked (make sure it is cooked through and hasnt just melted)

It’s also not safe to eat any sort of pate when you’re pregnant, including vegetable pate.

All forms of pate made from meat, vegetables or fish, may contain higher levels of listeria bacteria than other foods which, like soft cheeses, can lead to listeriosis.

If you become infected with listeria, you can get an illness called listeriosis. This causes flu-like symptoms which develop several weeks after you’ve been exposed to the bacteria. Even though listeriosis a fairly mild illness for you, it can cause serious health problems for your baby. It can even lead to miscarriage, or the loss of a baby at birth.

Listeriosis is rare and affects just one pregnancy in every 25,000. The risks to you and your baby are very low.

Eggs present a salmonella risk. to avoid this eggs should be cooked throughout without a runny yolk

Liver or liver products should be avoided as they contain high levels of vitamin A which in large quantities is harmful to your baby

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The Advice: if you’re carrying one baby and you’ve had an uncomplicated pregnancy then you can fly up to 36 weeks of pregnancy. However, airlines are sometimes unwilling to carry women who are more than 28 weeks pregnant because of the risk of premature labour.

Why?:  Flying during pregnancy can slightly increase your risk of thrombosis (blood clots) and varicose veins. Wearing support stockings (not tights, which increase your risk of developing thrush) when you fly will help keep your circulation flowing and relieve swollen veins. It’s also possible to buy knee-high socks which are specially designed for flying. For maximum protection, put the stockings or socks on before you get out of bed in the morning and keep them on all day.

There is a higher risk of dehydration in the pressurised cabin so ensure you drink lots and stay hydrated.

You may also have heard that exposure to natural atmospheric radiation while flying can increase the risk of miscarriage or abnormalities in unborn babies. Pregnant flight attendants and business travellers who fly hundreds of times a year may have a slightly higher risk of both. However, be assured that if you only fly a few times a year the risk is negligible.

Be realistic about the possibility of a medical emergency, too. Both on the flight and at your destination. Whenever possible, you should avoid travelling to places where emergency services are not readily available.

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Hair dye

Advice: It is widely believed that hair dying is thought to be safe during pregnancy. however some mothers are still anxious about the risks.
Why? It’s possible that a few of the chemical compounds in hair dyes could cause birth defects. However, you’d need to use them in extremely high doses for them to have this effect. The quantities would be far greater than the amount you’d use to colour your hair every month or two.

So, colouring your hair up to three to four times during pregnancy is probably safe. Plus, if you apply the dyes safely your body shouldn’t absorb many of the chemicals.

If you colour your own hair, follow the instructions carefully and apply the product for the minimum length of time stated. Also wear gloves and work in a well-ventilated room to reduce your exposure to the chemicals in the product.

You may want to highlight, paint, or frost your hair instead of dyeing it. You absorb hair colouring agents through the skin on your scalp, not through your hair shafts. So having highlights or streaks put straight onto your hair means you have less contact with chemicals.

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Advice: The Department of Health advises that alcohol should be avoided in pregnancy if possible.The National Institute for Health and Clinical Excellence (NICE) advises women who are pregnant to avoid alcohol in the first three months in particular, because of the increased risk of miscarriage.If women choose to drink alcohol during pregnancy they are advised to drink no more than one to two UK units once or twice a week, and avoid getting drunk. A unit equals half a pint of standard strength lager or beer, one shot (25ml) of spirits, while one small (125ml) glass of wine is equal to 1.5 UK units.

Why? If you drink alcohol when you’re pregnant, the alcohol crosses the placenta into the bloodstream of the unborn baby and could interfere with how it grows and develops. In the absence of its own blood filtering system, your baby is unprotected from any alcohol molecules that cross from your blood. If you drink too much alcohol during pregnancy it can permanently damage your developing baby’s cells. This could affect how your baby’s face, organs and brain grow.

Heavy drinking can also damage your baby’s nervous system. This can result in your baby having learning difficulties and problems with movement and coordination throughout his life.

Alcohol can cause damage to an unborn baby at all stages of pregnancy. Drinking during pregnancy has been associated with:

  • miscarriage (over 9,000 women are admitted to hospital every year for miscarriages caused by alcohol [NHS Information Centre Hospital Admission data])
  • low birth weight
  • heart defects
  • learning and behavioural disorders
  • The most severe of the alcohol-related conditions (which is normally due to heavy drinking in pregnancy) is Fetal Alcohol Syndrome (FAS). It causes:
  • facial deformities
  • problems with physical and emotional development
  • poor memory or a short attention span

A wider range of intellectual and physical disabilities than those seen in FAS and partial FAS-like syndromes occur in babies born to mothers who drank alcohol at some time in the pregnancy. These are commonly grouped together under the umbrella term Fetal Alcohol Spectrum Disorders (FASD).

While these effects attributed to alcohol are still more common in heavier drinkers, the problems also seem to happen at much lower drinking levels than seen for FAS.
It is not yet clear whether there is any small amount of drinking in pregnancy that might be completely safe from the risk of FASD. Therefore, pregnant women are advised to avoid all alcohol during pregnancy.

FASD and FAS-related disabilities carry on into adulthood, and because those effects due to drinking alcohol would have been completely prevented if the mother had not drunk during pregnancy, it is considered important to take a precautionary approach in advising on risk.

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Recreational drugs

The advice: Do not take recreational drugs at any stage in your pregnancy

Why? The effects of cannabis on your unborn baby are uncertain, but it’s thought to be harmful to your baby. Ecstasy can cause you to dehydrate and has also been linked to birth defects. Apart from adverse effects on your health, other illegal drugs such as cocaine, heroin and crack are addictive, as the drugs cross the placenta. This means your baby could be born with an addiction and will have to go through withdrawal after he is born.

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The advice: Limit your caffeine consumption to less than 200mg per day.

Why? High levels of caffeine during pregnancy can result in babies having a low birth weight, which can increase the risk of health problems in later life. Too much caffeine can also cause a miscarriage. The recommended limit is 200mg a day (see the table below for quantities found in common drinks).

The amount of caffeine found in some foods and drinks is:

  • one mug of instant coffee: 100mg
  • one mug of filter coffee: 140mg
  • one mug of tea: 75mg
  • one can of cola: 40mg
  • one can of energy drink: up to 80mg
  • one 50g bar of plain chocolate: up to 50mg
  • one 50g bar of milk chocolate: up to 25m

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The advice: Maintain a healthy weight during pregnancy, a BMI between 18.5 and 24.9
Why? More than half of women who die during pregnancy are overweight or obese. Obesity raises the risk of the following conditions in pregnant women:

Most pregnancies of obese women are successful, but problems for your baby can include:

There’s also evidence that babies born of obese mothers are more prone to health problems later in life, including obesity and diabetes.

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