Coffee and tea both contain certain amounts of caffeine in them. although there is a lot of information on the possible affects of caffeine (harmful or beneficial), the official word is that caffeine does not reduce the chance of fertility.
There is no solid medical evidence that caffeine consumption affects your chances of getting pregnant.
Similarly, there is no evidence that caffeine reduces sperm production or quality.
Once you are pregnant though, it is advisable for women to consume no more than 2 cups of coffee or tea per day as caffeine has been shown to reduce placental blood flow and therefore may lead to low birth weight babies.
Fertility can be affected by many factors such as lifestyle, diet, illness etc.
Some research suggests that overdosage of caffeine may affect fertility and people who are trying to conceive are advised to reduce their consumption of caffeine.
Coffee is able to keep one awake and increase urination. In TCM point of view, this suggest coffee can boost the body “Yang” and also to eliminate “dampness” from the body. Though most people can drink coffee without any serious consequence, those people with “dampness-heat” constituency may face problems after overconsumption of coffee.
The warm nature of coffee can destroy the “Yin” in the body easily and result in decrease in the kidney “Yin”. The kidney “Yin” plays an important role in fertility and its decrease may affect fertility.
For people who are trying to conceive, it is recommended to have a balanced diet and reduce consumption in coffee and alcohol.