Birth control experts cast
doubts on updated rhythm method
April 11, 2004
Researchers have refined the
outmoded birth control method, but it still has its sceptics, write Lucy
Beaumont and Prue Clarke.
Creators of a new take on the rhythm method of contraception say it is now a
viable, natural and reliable option for women, but Australian experts are
not so enthusiastic.
For decades it has been seen as a relic of the pre-sexual revolution era,
advocated by priests and grandmothers, and jokingly labelled "Russian
roulette". Now the rhythm method is making a 21st century comeback.
Researchers at Georgetown University, in the US, call their updated version
the Standard Days method. Using a computer model based on records of more
than 7500 menstrual cycles compiled by the World Health Organisation,
researchers have identified a 12-day window when a woman is fertile and can
become pregnant from unprotected intercourse. The old rhythm method relied
on temperature, vaginal discharge and guesswork.
"People used to think ovulation occurred 14 days before the end of the
cycle," explains Victoria Jennings, director of the Institute for
Reproductive Health. "We now know it is likely to occur at the mid-point of
the cycle or a few days either side, regardless of cycle length."
That means, for example, that a woman who has unprotected sex on the Tuesday
before the Saturday she ovulates has only a slight chance of becoming
pregnant. On the Wednesday that chance is greater and so on until the Sunday
after she ovulates, when she has very little chance of becoming pregnant.
The one caveat is that it will work only with women whose cycles are
reliably 26-32 days long. Luckily, that accounts for 80 per cent of the
population.
The Standard Days method comes with a set of coloured "cycle beads" that
allows women to chart their cycle. On day one a band is placed around the
first coloured bead. Each day it is moved one bead further until it reaches
the first of 12 white beads, which designate the days the woman is fertile
and should abstain from sex, or use some form of protection. Or if she wants
to become pregnant, the white beads identify when that is most likely.
In Australia, the oral contraceptive pill is the primary method of birth
control, reported by 40 per cent of contraceptive users, but 3 per cent
practise periodic abstinence from sex to avoid pregnancy.
Clinical trials have shown the Standard Days' failure rate is 5 per cent if
used properly, but Melbourne University sexual health professor Christopher
Fairley said that "perfect use" rates were misleading.
"You'll get 25 per cent of people pregnant with the rhythm method in the
first year of use," he said. "If the thing is used perfectly it might do
somewhat better, but it still doesn't come anywhere near other forms of
contraception."
Data published in The Lancet and cited by Professor Fairley, says the pill
has a failure rate of 5 per cent in the first year but 1 per cent in perfect
use. Male condoms lead to 14 per cent unwanted pregnancies in the first
year, but this rate falls to 3 per cent in longer term relationships when
they are used properly.
Standard Method's authors recommend women track their cycle on a calendar to
guard against slip-ups.
But Australian Women's Health Network convenor Helen Keleher said that
unless women were in "a stable long-term, monogamous relationship", they
should use condoms to protect them from sexually transmitted diseases.
The new rhythm method is gaining appeal, with more than 100,000 women
already said to be using it. Much of the institute's funding has come from
the USAID agency, which considers it a promising alternative to condoms and
birth control pills in developing countries.
"We've still got to promote condoms in those countries because of the
prevalence of AIDS, in particular, and gonorrhoea and syphilis," Dr Keleher
said. She urged women to be cautious when considering the method and only
use it if they were "absolutely certain" that they understood their cycle.
Researchers say Western family planning groups are increasingly offering the
Standard Method as an alternative for women wanting hormone-free,
non-invasive birth control.