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What it really takes to avoid getting pregnant
INSIGHT
AT INDIA’s largest burns centre in Victoria Hospital, Bangalore,
THERE’S a joke that goes: “What do you call people who use the rhythm method of contraception?” Answer: “Parents.” In spite of that, “natural” family planning methods – in which women forgo sex during the most fertile days of the month – can be as effective as the pill in preventing pregnancies, or so it was widely reported last week. In fact it’s not quite that simple. The study the reports were based on used a more sophisticated technique than traditional calendar and rhythm methods, which rely on counting the days since a woman’s period to identify the “non-fertile” days in her menstrual cycle. Instead, the so-called
www.newscientist.com
“symptothermal” method uses two direct physical checks. The first is the condition of cervical secretions, which become slippery and clear during a woman’s most fertile period. Then, when the secretions have ceased, the all-clear for contraception-free sex is signalled when her body temperature rises to 0.2 °C above normal on three consecutive days. Petra Frank-Herrmann of the University of Heidelberg, Germany, and her colleagues tested how well the technique worked for 900 women. Just 322 managed to stick fully to the procedure, completely abstaining from sex when it told them they could be fertile. For these women, the pregnancy
PIERRE BOURRIER/PHOTONICA
What it really takes to avoid getting pregnant
Still a more reliable method
rate over the course of a year was 0.4 per 100 women – just slightly higher than in women who take the pill, which gives a pregnancy rate of 0.3 per cent when used correctly (Human Reproduction, DOI: 10.1093/humrep/dem003). Not surprisingly, the rate was higher among women who had unprotected sex
during the “fertile” phase: 7.5 per 100 of them became pregnant. This figure is still quite low, says James Trussell of Princeton University, whose research suggests that “natural” methods fail 25 per cent of women in the first year of use, compared with 8 per cent for incorrectly taken pills. Frank-Herrmann suggests that figures for the women in her trial were lower because they risked unprotected sex only at the fringes of the fertile period. Trussell thinks the best contraceptives are those that can be fitted and forgotten about – such as implants and intrauterine devices. Ann Furedi of the British Pregnancy Advisory Service agrees. “Circumstances in which sex takes place are not always ones you can plan for,” she says. The symptothermal method is fine for some “highly motivated” couples, she says, but would not suit the majority. Andy Coghlan ●
3 March 2007 | NewScientist | 15
AT INDIA’s largest burns centre in Victoria Hospital, Bangalore,
THERE’S a joke that goes: “What do you call people who use the rhythm method of contraception?” Answer: “Parents.” In spite of that, “natural” family planning methods – in which women forgo sex during the most fertile days of the month – can be as effective as the pill in preventing pregnancies, or so it was widely reported last week. In fact it’s not quite that simple. The study the reports were based on used a more sophisticated technique than traditional calendar and rhythm methods, which rely on counting the days since a woman’s period to identify the “non-fertile” days in her menstrual cycle. Instead, the so-called
www.newscientist.com
“symptothermal” method uses two direct physical checks. The first is the condition of cervical secretions, which become slippery and clear during a woman’s most fertile period. Then, when the secretions have ceased, the all-clear for contraception-free sex is signalled when her body temperature rises to 0.2 °C above normal on three consecutive days. Petra Frank-Herrmann of the University of Heidelberg, Germany, and her colleagues tested how well the technique worked for 900 women. Just 322 managed to stick fully to the procedure, completely abstaining from sex when it told them they could be fertile. For these women, the pregnancy
PIERRE BOURRIER/PHOTONICA
What it really takes to avoid getting pregnant
Still a more reliable method
rate over the course of a year was 0.4 per 100 women – just slightly higher than in women who take the pill, which gives a pregnancy rate of 0.3 per cent when used correctly (Human Reproduction, DOI: 10.1093/humrep/dem003). Not surprisingly, the rate was higher among women who had unprotected sex
during the “fertile” phase: 7.5 per 100 of them became pregnant. This figure is still quite low, says James Trussell of Princeton University, whose research suggests that “natural” methods fail 25 per cent of women in the first year of use, compared with 8 per cent for incorrectly taken pills. Frank-Herrmann suggests that figures for the women in her trial were lower because they risked unprotected sex only at the fringes of the fertile period. Trussell thinks the best contraceptives are those that can be fitted and forgotten about – such as implants and intrauterine devices. Ann Furedi of the British Pregnancy Advisory Service agrees. “Circumstances in which sex takes place are not always ones you can plan for,” she says. The symptothermal method is fine for some “highly motivated” couples, she says, but would not suit the majority. Andy Coghlan ●
3 March 2007 | NewScientist | 15