‘What foods should I avoid?’ is one of the first questions people ask once a pregnancy is confirmed. Prenatal Dietitian Melanie McGrice looks at some of the key foods to avoid during pregnancy.

Foods to Avoid during pregnancy

1. Foods high in mercury   
Mercury is a naturally occurring metal that is found in trace amounts in water and food. Mercury can build up over time during pregnancy, and high levels in the blood stream can be harmful to the baby, particularly on their nervous systems.

When a baby is exposed to high levels of mercury, the effects are often not noticed until developmental milestones, such as walking and talking, are delayed. Memory, language and attention span may also be affected.

Levels that would normally be safe for an adult can pass through the placenta and bind to the baby’s nervous system and impair their development.

For pregnant women, it is important to limit fish or seafood that contains high amounts of mercury [1]. These include marlin, broadbill, swordfish, shark (flake), king mackerel, orange roughy, catfish and tilefish .

Pregnant women should instead eat fish low in mercury, such as salmon [2].

To learn more, watch video by Melanie here

2. Foods with high levels of listeria 
Listeria refers to an illness caused by eating foods contaminated with the pathogenic bacterium Listeria Monocytogenes. Infection with listeria, also known as listeriosis, can cause severe health consequences, including meningitis and blood poisoning which can lead to miscarriage or stillbirth.  Raw or undercooked meat, poultry, seafood or eggs may also increase the risk of toxoplasmosis and salmonella toxicity.  Consequently, it is recommended that foods are well cooked and that good food hygiene practices are used.

The immune systems of healthy adults are strong enough to avoid contracting severe illness from consuming the bacteria, but there is a high fatality rate of 20–30% for those who are vulnerable [3]. More than 25% of all listeriosis cases are pregnant women [4].

Foods at high risk of listeria toxicity include pre-packaged and pre-prepared salads, ready-to-eat or raw seafood, unpasteurised juices and milk, deli foods (including ham, salami and paté), soft serve ice-cream and soft cheeses.

3. Foods contaminated with BPA
BPA, or bisphenol A, is a chemical used in the production of polycarbonate plastics. It has been found to impact hormones [5] and, although the evidence is limited, studies suggest that it may play a role in infants who are small for gestational age [6].

As such, it is generally recommended that women trying to conceive, pregnant mothers and infants have minimal exposure.

The best ways to minimise intake of BPA are to:

• avoid putting plastic containers in the dishwasher or microwave
• use glass, porcelain or stainless steel containers for hot foods and liquids
• limit the intake of canned foods
• look for foods with a BPA-free plastic.

4. Some artificial sweeteners
Although sugar substitutes are generally safe during pregnancy, research is limited [7].

It is important to be aware that many sugar substitutes do cross the placenta [8]. Furthermore, some small studies have shown that sugar substitutes have been associated with preterm delivery [9] and affecting genetic programming to result in obesity later in life [10].

Consequently, pregnant women should be advised to avoid large intakes of sugar substitutes where possible.

5. Discretionary foods
A high intake of discretionary foods [11] (which do not fit into the five food groups and are not necessary for a healthy diet) during pregnancy has been linked to paediatric mental health issues [12].

In addition, a recent review covering more than one million pregnancies found half of the women gained too much weight [13]. Excess weight gain has been linked to a higher risk of developing diabetes in pregnancy, high blood pressure, complications during birth and childhood obesity [14] [15] [16].

As such, discretionary foods should be limited during pregnancy.

6. Alcohol
The Australian guidelines to reduce health risks from drinking alcohol recommend that the safest option is to not drink alcohol if you are pregnant [17].

However, an epidemiological study found that alcohol consumption during pregnancy is prevalent and socially acceptable, with more than 40% of pregnant Australian women drinking at least once during pregnancy, and 17% continuing to drink in their second trimester [18].

Alcohol crosses the placenta and consumption can lead to miscarriage or foetal alcohol syndrome.

Although there are foods to limit or avoid during pregnancy, the most important consideration is providing a nutritious prenatal diet.

This article was originally published on RACGP and has been adapted for dietitians