By NUH Women’s Centre



What nutrients are needed to increase the chances of conception and what kind of food should be eaten or avoided?
There is no particular dietary component that will promote fertility. Folk traditions have made many contributions with regard to food intake benefiting fertility. However, evidence based research has not found any conclusive advice to date, except that the prenatal intake of folic acid is essential in the prevention of neural tube defect in the foetus.


What are some common beverages and food that contain high levels of caffeine?
Caffeine occurs naturally in a range of foods, such as coffee, tea & chocolate. It is also found in some soft drinks (for example, cola soft drinks) and "energy" drinks (for example, Red Bull).


It is normally recommended that for an average person, no more than 300mg of caffeine should be consumed a day, which is roughly equivalent to the caffeine level found in three mugs of instant coffee, three cups of brewed coffee, six cups of tea, eight cans of cola soft drinks, or eight standard bars of chocolate.


How does caffeine affect fertility and to what extent?
Caffeine has been said to affect human fertility for decades. To date, we do not know the exact mechanism underlying caffeine's effect on fertility, but human epidemiology studies have essentially limited the effect to an increased ‘time to pregnancy’ (which is defined as the time interval to become pregnant without use of contraception).


When compared to non-smoking non-caffeine users, the non-smoking heavy caffeine users’ (who consumed more than or equal to 300 mg per day) risk of waiting for more than or equal to one year before conception is increased by 2.65 folds (Stanton & Gray, Am J Epidemiology 1995). A large multi-centre European study also found that the risk of delayed conception by more than or equal to 9.5 months in the first pregnancy is increased by 45% among women who drank more than or equal to 500mg per day of caffeine (Bolumar, Am K Epidemiology 1997).


Caffeine use may also affect other aspects of reproductive health. The daily heavy use of caffeine has also been related to increased risk of early pregnancy loss (Cnattingius, NEJM 2000). An article in the American Journal of Obstetrics & Gynecology demonstrated that daily heavy use of caffeine during pregnancy increased the risk of miscarriage to the extent of two folds when more than or equal to 200mg caffeine is consumed per day (Xiaoping W, AJOG 2008). Another study however concluded that caffeine use (with the median use being more than or equal to 200mg per day in the study) had little miscarriage risk (Svavitz, Epidermiology 2008). Although the general belief is that heavy caffeine use of more than or equal to 300mg per day may increase pregnancy loss in the first trimester, we are not absolutely certain.


To date, it is still controversial whether heavy use of caffeine during pregnancy will give rise to growth restricted babies (babies born below the 10th centile growth). Some studies suggested lower birth weight in caffeine users (Fortier, AJ Epidemiology 1993). Other studies, however, did not find such a direct causative relationship (Clausson, AJ Epidemiology 2002).


In summary, heavy caffeine use appeared to have several negative effects on reproductive health, but it has not been entirely proven. So the message may be that sensible use of caffeine may not be detrimental to reproductive health.


Will a woman's caffeine tolerance have an impact on how their fertility is affected?
Caffeine tolerance develops very quickly, usually achieved by sustained high daily intake (more than 1g per day) over two to three weeks. A woman's tolerance to the effect of caffeine does not reduce the influence of caffeine on fertility or the pregnancy. Caffeine has a direct dose effect, that is, the higher the intake, the more significant the impact.


Now that I am pregnant, can I still have my cup of coffee every morning? Can I have more than one cup of coffee every day? I don't drink alcohol very often either but do like to have a social drink every once in a while. Is it acceptable to occasionally drink alcohol during pregnancy?
High caffeine levels have been associated in some researches with low birth weights and miscarriages. Health authorities in UK have recommended not more than 200mg of caffeine per day. One mug of instant coffee contains 100mg of caffeine. Other food containing caffeine content includes tea, chocolates and cola soft drinks. Therefore, drink in moderation.


Some health authorities (for example, UK Department of Health/ National Institute of Clinical Excellence) have advised pregnant women and women trying to conceive to avoid drinking alcohol. The reason being alcohol can increase the risk of miscarriage during the first three months of pregnancy.


The Royal College of Obstetricians and Gynaecologists (RCOG) UK recommends that "the safest approach in pregnancy is to choose not to drink at all" and that "small amounts of alcohol during pregnancy (not more than one to two units, and not more than once or twice a week) have not shown to be harmful".


One unit of alcohol is the equivalent of a half a pint of lager or beer, a glass of wine or a single shot of a spirit (gin, vodka, and rum). In addition to increasing the risk of miscarriage, alcohol abuse during pregnancy also results in a condition called Fetal Alcohol Spectrum Disorder (FASD) in babies. FASD babies may be mentally retarded and may have defects in the brain.


Does caffeine affect men's fertility?
Heavy caffeine use has been suggested to negatively affect sperm count and functions.


What are some other ways to improve your fertility chances?

  •  Consider starting the family at an earlier age.
  •  Exercise regularly.
  •  Adopt a diet that is low fat, rich in vitamins & minerals.
  •  Avoid smoking & passive smoking.
  •  Avoid drugs and excessive alcohol intake.
  •  Good stress management strategies.

For more information, you may contact the Women's Clinic at (65) 6772 2255 / 2277, or email to


This featured article is contributed by the NUH Women’s Centre, National University Hospital. Please visit to read more.


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