A new study published in the journal BMC Medicine last month shows that caffeine is linked to low birth weight babies (1).
Caffeine intake is already a concern in pregnancy, with current guidelines recommending that pregnant women restrict themselves to no more than 200mg of caffeine (equivalent to around two cups of coffee) each day.
While the placental barrier does a good job of screening out many infectious agents, it is not able to block environmental pollutants such as pesticides, mercury and PCBs. Likewise, caffeine can cross the placental barrier, resulting in babies that are small for gestational age (SGA).
The study monitored the caffeine intake of more than 60,000 pregnant women. For every 100mg of caffeine each day, the average infant lost an estimated 21-28g. Caffeine intake also increased the length of pregnancy, with caffeine from coffee in particular having the most dramatic effect. This suggests that another substance in coffee may also contribute to the negative effects. For example, decaffeinated coffee retains other stimulants such as theophylline and theobromine.
While coffee is the primary source of caffeine in many diets, there are many other foods and drinks that contribute to overall caffeine intake. This study monitored all sources of caffeine, including coffee, tea, hot chocolate, fizzy drinks, as well as foods such as chocolate and chocolate desserts.
As a general guide, a can of coke contains around 30mg caffeine, a cup of tea contains around 50mg caffeine, and a cup of instant coffee contains around 60mg caffeine. ‘Proper’ coffee will provide an even bigger caffeine hit. A medium cup of coffee from a high street coffee chain can contain around 200mg caffeine. For those who regularly visit high street coffee chains it’s important to note that the amount of caffeine in drinks from these stores can vary wildly making it very difficult to determine how much caffeine you are actually drinking.
Staying hydrated is especially important during pregnancy. Drinking plenty of fluids helps lessen the risks of problems such as constipation, urinary infections, fluid retention and haemorrhoids during pregnancy. The volume of blood in your body, which is made mostly of water, also increases during pregnancy.
So what are the best choices of beverage during pregnancy? Water is the most obvious choice for staying hydrated. Keep a bottle at your desk or carry a small bottle in your bag if you’re out and about. If plain water is too boring, try carbonated water and add a slice or two of lemon or lime.
Naturally caffeine-free teas are another good choice. Redbush tea is naturally caffeine free. Peppermint tea can help ease digestive troubles and ginger tea may help to relieve morning sickness. Fruit smoothies using probiotic yoghurt and digestive-boosters such as milled flax seeds is another great option.
Barley water makes a great anti-inflammatory agent for the urinary system which can be more prone to infection during pregnancy. Buy whole barley, put 40g in a litre of water, boil and simmer for 20 minutes. Add a slice of lemon or the juice of one lemon and simmer for a further 10 minutes. Allow to cool, then sip the water throughout the day.
Finally, green smoothies provide all the antioxidants of fruit juice without the sugar hit, and they can be a great source of minerals such as folate and iron which are needed in greater amounts during pregnancy. Try blending a handful of spinach with an avocado, a dash of apple juice, a cup of water, and three tablespoons of plain yoghurt for a refreshing folate and iron-rich green smoothie.
1. Sengpiel V et al. (2013) Maternal caffeine intake during pregnancy is associated with birth weight but not with gestational length: results from a large prospective observational cohort study. BMC Medicine 11:42.