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Monday’s medical myth: the pill affects long-term fertility

The combined oral contraceptive pill is the most popular form of contraception in Australia and is taken by an estimated 100 million women worldwide. The pill’s most obvious use is to prevent pregnancy…

Some women question the long-term impact of the contraceptive pill on their fertility. J. Stephen Conn

The combined oral contraceptive pill is the most popular form of contraception in Australia and is taken by an estimated 100 million women worldwide.

The pill’s most obvious use is to prevent pregnancy. But it’s also prescribed to treat acne, regulate periods, alleviate menstrual pain and reduce the symptoms of conditions such as endometriosis and polycystic ovarian syndrome.

The average duration of pill use is estimated to be about three to five years, but varies widely by country.

Research suggests that most women want to promptly return to their pre-pill fertility levels when they stop taking the contraceptive. But some women have difficulty falling pregnant after ceasing the pill, leading them to question whether the contraception affected their long-term fertility.

This myth is so pervasive that researchers have identified fear of infertility as a key reason for women avoiding this effective form of contraception.

How does the pill work?

The pill works by effectively switching off a woman’s natural production of ovarian oestrogen and progesterone and replacing this with a synthetic version of both hormones. This sets off a number of mechanisms: inhibiting egg release (ovulation), changing the consistency or thickness of cervical mucus and altering the lining of the womb so that implantation of a fertilised egg is less likely.

Variables in different pill formulations make it difficult to determine general effects of “the pill”. Alicakes

The early contraceptive pill used much higher doses of hormones than currently available pills, which also vary in their dose of hormones. Most pills contain the oestrogen ethinyl oestradiol and there are a number of different synthetic progesterone-like compounds in different pill formulations.

Women often try a number of pills throughout their reproductive lifetime and, unsurprisingly, find it difficult to recall the exact duration they’ve taken a particular pill. All these variables mean it’s difficult for researchers to make general conclusions about the effects of “the pill”: it’s not just one particular hormonal agent taken for a defined time in one particular group of women.

Fertility

A woman’s fertility declines with age, particularly from 36 or 37 years and this is, in part, genetically determined.

Fertility is also affected by general and gynaecological health, concurrent illness, weight, exercise levels, cigarette smoking and stress. Weight above and below the recommended range for height can have an impact on fertility.

Health-based fertility problems are often signalled by irregular or absent menstrual cycles. This is one of the body’s natural “safety valves” to protect against pregnancy when the health of the foetus or mother may be at risk.

Long-term effects of the pill

It’s difficult to assess the effects of the pill on a woman’s fertility when so many other factors may be contributing. Some women will return to their normal levels of hormone secretion within a couple of days of ceasing the pill. Others may take up to six or 12 months. But the majority of women will return to normal within the first few months.

The very limited evidence we have suggests the pill has no overall effect on long-term fertility. A review of studies comparing reversible forms of contraception found between 79% and 96% of women were able to get pregnant in the 12 months after they stopped taking the pill.

Another study reported that pill users who ceased the pill in order to become pregnant had some delay in conceiving. But this impairment of fertility was temporary and limited to the first few months after coming off the pill.

Overall, the pill - when taken as directed - is extremely effective at inhibiting fertility in the short term. With the evidence showing no long-term impact on fertility, this myth is no reason to avoid the pill.