Some treatments for infertility, such as IVF, can cause complications.
multiple pregnancy – if more than 1 embryo is placed in the womb as part of IVF treatment there's an increased chance of having twins; this may not seem like a bad thing, but it significantly increases the risk of complications for you and your babies
ectopic pregnancy – the risk of having an ectopic pregnancy is slightly increased if you have IVF
There are many possible causes of infertility, and fertility problems can affect either partner. But in a quarter of cases it is not possible to identify the cause.
Common causes of infertility include:
lack of regular ovulation (the monthly release of an egg)
poor quality semen
blocked or damaged fallopian tubes
endometriosis – where tissue that behaves like the lining of the womb (the endometrium) is found outside the womb
There are also several factors that can affect fertility.
age – fertility declines with age
weight – being overweight or obese (having a BMI of 30 or over) reduces fertility; in women, being overweight or severely underweight can affect ovulation
sexually transmitted infections (STIs) – several STIs, including chlamydia, can affect fertility
smoking – can affect fertility: smoking (including passive smoking) affects your chance of conceiving and can reduce semen quality; read more about quitting smoking
alcohol – the safest approach is not to drink alcohol at all to keep risks to your baby to a minimum. Drinking too much alcohol can also affect the quality of sperm (the chief medical officers for the UK recommend adults should drink no more than 14 units of alcohol a week, which should be spread evenly over 3 days or more)
environmental factors – exposure to certain pesticides, solvents and metals has been shown to affect fertility, particularly in men
stress – can affect your relationship with your partner and cause a loss of sex drive; in severe cases, stress may also affect ovulation and sperm production
There's no evidence to suggest caffeinated drinks, such as tea, coffee and colas, are associated with fertility problems.