Chocolate, cappuccinos, tea, tiramisu… a lot of us love our daily caffeine fix! But how does caffeine affect fertility and is it safe for pregnancy?
In Melbourne, the home of great coffee, a daily strong latte is pretty much the norm. The average woman consumes 100mg of caffeine each day, with the top 10% of caffeine consumers exceeding 229mg each day.
So why does coffee make us feel good? Caffeine is a central nervous system stimulant and it is addictive, capable of causing withdrawal affects if you are used to your fix and a feeling of wellbeing when you get it. Other body systems are affected as well including the cardiovascular system (increased heart rate and blood pressure) the renal system (acts as a diuretic so that the kidneys make more urine) and the metabolic rate (revs it up).
Many studies have suggested that caffeine consumption increases the risk of miscarriage. Pregnant women may be more sensitive to caffeine as it is broken down slower during pregnancy. An additional concern in pregnancy is that caffeine can cross the placenta and directly affect the developing baby.
Caffeine may also impact your ability to become pregnant. Study results reporting caffeine use and time taken by participants to conceive have reported mixed results, some positive some negative. Many of these studies involve retrospective reporting of caffeine use. This means the study design is considered to be of low scientific quality and consequently results should be interpreted with caution.
One well designed prospective study of 104 women attempting pregnancy showed women who consumed less than one cup of coffee were twice as likely to become pregnant, per month, as moderate coffee drinkers and the risk of not becoming pregnant increased with higher caffeine intake. In a study of IVF patients, increased caffeine intake was found to be a risk factor for not achieving a live birth (either by not becoming pregnant or by having a miscarriage). While the exact mechanism by which caffeine affects fertility is unknown, the answer may be related to the ability of caffeine to influence the quality of the developing egg. Preliminary studies in mice and monkeys suggest caffeine may inhibit the fertile egg’s maturation process. Caffeine is also thought to perhaps affect ovulation and corpus luteum functioning by causing changes in hormone levels.
Most studies indicate that the bad effects of caffeine are related to the amount that is consumed. In this context it is sensible for women contemplating pregnancy to limit their caffeine intake. No real cut off or threshold for adverse effects is known. My advice to my patients who don’t want to cut out coffee and chocolate all together, is to set your limit at one expresso coffee per day and keep chocolate as a special treat rather than an “everyday food”.
Soft drinks like coca-cola have very little nutritional merit – lots of caffeine and sugar, not to mention other chemicals. I believe they are best avoided in general and more so in pregnancy.