Women over the age of 35 are being warned to keep using their contraception because the message on infertility and age has gone "too far", Sky News reported Tuesday.
Although fertility declines as women get older, the "constant stream" of information about it could be encouraging older women to abandon contraception and risk unplanned pregnancy, the Family Planning Association (FPA) said.
Data for England and Wales shows abortion rates among women aged 40 to 44 are the same as for under-16s - four per each 1,000 women.
Other figures from the Office for National Statistics reveal women between 30 and 34 continue to have the highest fertility rate, at 113.1 per 1,000 women.
But the rate among women aged 40 and over has more than doubled since 1988, from 5.1 to 12.6 per 1,000 women, with more than 26,000 live births to women in this age group in 2008.
Launching its new campaign, Conceivable?, the FPA warned that age alone is not a barrier to birth.
Julie Bentley, chief executive of the charity, said women should keep using contraception until after the menopause if they want to avoid pregnancy.
The message about infertility is being "overplayed", says the FPA.
"Whilst the message about fertility declining with age is an important one, it is often overplayed, alongside disproportionate messaging about unplanned teenage pregnancies," she said.
"It sends an inaccurate message to women and society that only the young become pregnant and is leading older women to believe their fertility has gone long before it actually has.
"It's important that women realize it's entirely conceivable that just one night of unprotected sex in your late 30s, 40s, even 50s can end in an unplanned pregnancy.
"Our helpline receives calls from such women, shocked this has happened to them. They thought their age would protect them from becoming pregnant."
Bentley said there are 15 methods of contraception, all of which are suitable for the over-35s.
"We know on average women spend about five minutes on choosing their contraception and many don't make enough time for themselves to think about what they want.
"They can talk to FPA or their health professional about finding the perfect contraceptive for them."
The live birth rate is 58.4 per 1,000 women aged 35 to 39.
Meanwhile a new report by the International Planned Parenthood Federation is advocating that children as young as 10 be given extensive sex education, including an awareness of sex's pleasures.
The report demands that children 10 and older be given a "comprehensive sexuality education" by governments, aid organizations and other groups, and that young people should be seen as "sexual beings".