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
What causes infertility?
There are many possible causes of infertility, and fertility problems can affect either the man or the woman. But in a quarter of cases it isn't possible to identify the cause.
In women, common causes of infertility include:
lack of regular ovulation, the monthly release of an egg
blocked or damaged fallopian tubes
endometriosis – where tissue that behaves like the lining of the womb (the endometrium) is found outside the womb
In men, the most common cause of infertility is poor-quality semen.
There are also a number of factors that can affect fertility in both men and women.
age – female fertility and, to a lesser extent, male fertility decline with age; in women, the biggest decrease in fertility begins during the mid-30s
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 in both sexes: smoking (including passive smoking) affects a woman's chance of conceiving, while in men there's an association between smoking and reduced semen quality; read more about quitting smoking
alcohol – for women planning to get pregnant, the safest approach is not to drink alcohol at all to keep risks to your baby to a minimum; for men, drinking too much alcohol can affect the quality of sperm (the chief medical officers for the UK recommend men and women 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.
To find out more about what you can do to protect your fertility, see: