Debunking pregnancy nutrition myths, one trimester at a time

By Cary Davies

15 February 2024

There are many old wives tales – some wiser than other tales- pertaining to the perfect pregnancy diet. Furthermore, due to the enormously varied range of diet styles advocating optimum nutrition, falling pregnant can create some overwhelm about where to start. However, amongst the myths, facts, restrictions, superstitions and evolving science, nutritional recommendations for a healthy pregnancy can be easily simplified into ‘bite-size’ steps for each trimester.

The first trimester

Diet style: Whether your pre-pregnancy eating preferences were Low GI, Low Fat, Mediterranean or multifaceted- it is unlikely that dramatic changes will be necessary. Many dietary lifestyles can accommodate a healthy pregnancy and there is no longer a one-size-fits-all approach. Instead, modern medicine regards optimum nutrition to be highly individualised- it all boils down to genetics. Click here to find out more about DNA testing for nutritional well-being.

Eating for two: Despite the widely accepted view of ‘eating for two’, no additional calories are required during the first twelve weeks of pregnancy -unless you were underweight beforehand.

Vitamin top-up: Starting a pregnancy-specific multivitamin and omega three supplement is advisable. This can be regarded as ‘nutritional insurance’ against deficiency states, as micronutrients will not cross the placenta if maternal stores are deficient. Pregnancy-specific multivitamins are designed to support the exact micronutrient needs of pregnancy, including additional requirements for  folic acid, calcium and iron.

Smoking: Smoking retards the delivery of nutrients and oxygen to the fetus and should therefore be avoided throughout your pregnancy.

Alcohol: Alcohol crosses the placenta and accumulates in fetal tissues. Depending on the volume of consumption, this may result in congenital abnormalities and fetal growth retardation. Avoidance of alcohol is especially important during the earlier stages of your pregnancy when fetal organs are being formed.

Caffeine also crosses the placenta and has been associated with increased risk of miscarriage in the first trimester. Scientific consensus suggests limiting coffee intake to two cups per day in order to reduce the risk of pregnancy loss and low birth weight outcomes.

Food safety: Food poisoning can be detrimental to your fetus, which is why pregnant women are advised to adopt firm food hygiene principles. Although mouldy cheeses, (such as Brie and Camembert) and raw foods (such as biltong, sashimi and raw eggs) are often restricted in the nutritional literature due to their heightened potential for bacterial contamination, many sources disregard dietary restriction on the grounds of increased health and safety standards within the highly regulated current-day food industry.

Provided that your food comes from a reputable establishment, is properly stored and handled and is consumed within its expiry date - the risk of food-borne illness is unlikely.

Methyl-mercury: Certain seafood varieties (shark, swordfish, marlin, fresh tuna and yellow-tail) are prone to accumulation of high levels of methyl-mercury, consumption of which could result in heavy metal poisoning that would be detrimental to the growing brain of your fetus.

Pregnant women are, therefore, advised to choose low-mercury varieties of seafood (salmon, trout, tilapia, cod, sole, sardines, shrimp, oysters and other shellfish.)

Morning sickness: Although some studies have reported a higher frequency of nausea and vomiting in pregnant women carrying a female fetus, the evidence is not conclusive and this cannot be used as a predicter of fetal sex. Click here to find out more about MiniMi Early Fetal Sex Testing at 10 weeks of pregnancy.

Dietary management of morning sickness includes choosing plain, bland foods; avoidance of fatty foods and foods with a strong odour; eating smaller meals and regular consumption of ginger tea.

The second trimester

By 13 weeks of pregnancy, morning sickness is most likely to subside and your appetite is simultaneously bound to increase. 

Weight gain: Although weight loss may occur in the first trimester- as a result of nausea and vomiting- healthy weight gain is essential from this point onwards.

Expected average weight gain during the second and third trimesters is 300-500g per week (650g for twins) and the minimum weight gain requirement during this time is one kilogram per month.

Additional energy requirements: An additional 200-300 calories per day is now required to support your growing fetus. However, your increased energy needs should not be used as an excuse to overindulge on junk foods, as high calorie foods with low micronutrient value will have little benefit.

Low iron stores: Pregnancy results in the increase of blood volume over time, with a simultaneous decrease in the percentage of iron in your blood.

Adequate iron intake for pregnancy can be difficult to meet with an average diet, thus supplementation during the second and third trimesters is necessary. The iron requirements for pregnancy should be included in a pregnancy-specific multivitamin, however, your health care provider may suggest an additional iron supplementation if deemed necessary.

The third trimester

Maximum growth: The fetus accumulates most nutrients during the last stage of pregnancy, which makes this a significant time to optimise and maintain healthy eating habits.

Heartburn: Pressure on your stomach from the growing fetus, may cause acid reflux into your esophagus.

In order to reduce the discomfort of heartburn, it is advisable to chew your food slowly; to eat smaller, more frequent meals; to avoid fizzy drinks and spicy foods; to avoid lying down for at least an hour after a meal and to sleep in an elevated position.

Leg cramps: Leg cramps may result from a magnesium deficiency, commonly associated with late pregnancy and breastfeeding. This can be easily corrected with an additional magnesium supplement.

The fourth trimester

Although not widely recognised, this newly coined term for the first twelve weeks following the birth of your baby, should be regarded as an equally important time for management of physical, nutritional and mental health.

Continuation of dietary supplements and additional calories will be necessary to support breastfeeding and adequate hydration to achieve optimum milk volumes is essential. However, beyond the needs of lactation, this is a critical time to ensure sufficient rest and emotional support for the new mother.

Lastly, according to an article in the Medical Journal of Maternal/Child Nursing, careful management of gut health is a key postpartum priority- as sleep deprivation and unmet dietary needs can disrupt the maternal microbial balance, which may in turn magnify post-partum depression.

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