Dr. Wilf Steinberg calls it the unicorn theory. He is talking about some of the beliefs held by teens about contraception. For example, you can only get pregnant if you have an orgasm. Or, you can't get pregnant the first time you have sex. The gynecologist and assistant professor, department of obstetric and gynaecology at the University of Toronto, has heard it all. But this fantasy thinking is not limited to teens. In fact, many women aged 40 and beyond believe their age is contraception enough.

Consider the statistics: Approximately 50% of pregnancies in Canada are unintended; 50% of these pregnancies occurred to women using some form of contraception.

"Other than the under-age-18 group, the highest proportion of unplanned pregnancies is in the age group 40-plus," says Dr. Alfred Yuzpe, emeritus professor of obstetrics and gynecology from the University of Western Ontario and co-founder and co-director of the Genesis Fertility Centre in Vancouver.

"A lot of these women are using contraception, but less-than-ideal methods," Dr. Yuzpe says. "The irony is that as physicians, we stress that fertility declines in women over the age 40. So many women have a false sense of security."

And it is false. To put it into perspective, almost 200,000 unintended pregnancies occur each year in Canada. "This is wholly unacceptable," Dr. Steinberg says. "And treating these failures, whether by terminating a pregnancy or having the child -- these are failing strategies that don't enhance our societal values. Nor do they take into account many of the physical and emotional problems unplanned pregnancies produce."

Dr. Steinberg says there are three reasons the failure rate is so high: information, motivation to use the contraception appropriately and behavioural skills (in other words, a mindset to use a contraceptive). "My take-home message is: There are safe and effective methods of contraception for women over 40 that have the ability to prevent 99% of all pregnancies. These methods are not only safe, effective and beneficial for family planning, they also all carry various noncontraceptive benefits that are specific to their individual use."

Take oral contraceptives, for example. Mature women over 40 have irregular menstrual cycles that can be socially and physically disabling, leading to the need for operative intervention including hysterectomy. "Oral contraceptives, because they regulate the menstrual cycle, have the added benefit of reducing the need for operative interventions as well as reducing the physical and emotional discomfort of abnormal bleeding," Dr. Steinberg says. "As well, it has been proven and re-proven that there is a 50% reduction of ovarian cancer and cancer of the uterus in women who take the birth control pill for more than five years."

Dr. Steinberg calls the levonorgestrel-releasing intrauterine system a "rising star" in the area of long-term intrauterine contraception. "It has the added benefit of reducing menstrual flow and menstrual pain in women of all ages but especially in women over the age of 40. In my clinical practice, I can tell you I avoid doing surgery on a woman with abnormal bleeding until she has completed a trial with an oral contraceptive or intrauterine system. What's more, it's reversible."

Choosing a right method of contraceptive for an individual's lifestyle is absolutely essential. "A right method has a lot of facets," Dr. Yuzpe says. "Efficacy is one. There are two types of failure rate for any method of contraception: There is the theoretical failure rate and the use-effectiveness failure rate. That means once you put it in the hands of the consumer, how effective is it? A classic example is the birth control pill. The theoretical failure rate is one in 1,000. The practical failure rate is five to seven in 100. When a method has to be used daily, compliance often becomes an issue. Condoms are very effective but they need to be used. The biggest reason they fail is they are not put on at the appropriate time or they break."

Dr. Yuzpe suggests women ask themselves the following questions when deciding on an appropriate method of contraceptive:

* Have you completed your family or not? If they haven't, then they want to choose a method that is quickly reversible and will return them to normal fertility rates.

* What is your tolerance for failure? In other words, how effective does the method need to be?

* How acceptable is the method to them?

"There is no one method that is perfect for everyone. Every one has their own preferences. You have to think about yourself," Dr. Yuzpe says. "Women have to be their own advocate, ask what their choices are, the ups and downs of each, and then they can make their choice on an informed basis. Unfortunately, that doesn't happen often enough."