Morning-after pill ‘may not work if you weigh more than 11 stone’
THE morning-after pill may not work for women over 11 stone, according to sexual health experts.
They have issued new guidelines stating that the contraceptive may be diluted or broken down too quickly by their bodies, even though 11 stone is the weight of the average British woman.
Women who are overweight – with a body mass index over 26 – are also being warned that the pills may be ineffective.
They are being urged to take two pills as a precaution or consider using the emergency coil instead.
The advice has been issued by the Faculty of Sexual and Reproductive Healthcare which represents 15,000 specialist doctors and nurses. The organisation is concerned that the drug is diluted in larger women or broken down more quickly by their bodies, rendering it ineffective.
Dr Jane Dickson, its vice president, said: ‘The morning-after pill works by delaying or interfering with the release of eggs and disrupting fertilisation through delivering a higher dose of the hormone progestin that is found in regular birth control pills.
‘We believe there is evidence to suggest that in heavier women, the drug may be less effective because the drug is diluted in their blood stream.
‘The 11 stone (70 kg) figure is based on research. It is something of an arbitrary figure and it may be 15 stone is the danger point for some women. But for safety 11 stone or a BMI over 26 is the level we can say weight may create a risk.’
Dr Dickson explained that larger women worried about pregnancy after contraception failure or unprotected sex could take two morning-after tablets.
FSRH is recommending health professionals advise women that an intrauterine device (IUD, or the coil) is the best emergency contraception.
Dr Dickson said: ‘The coil’s effectiveness is not affected by a woman’s weight as it works differently to prevent fertilisation – it’s toxic to sperm and eggs and works locally. And weight issues aside, it is more effective than the morning-after pill.’ There are two kinds of emergency contraceptive pill. Levonelle has to be taken within 72 hours – three days – of sex, and ellaOne, which must be taken within 120 hours – five days. Both work by preventing or delaying ovulation – the release of an egg.
Trials suggest the failure rate for the IUD as emergency contraception is lower than one per cent.
However, research reveals that 95 per cent of women are issued the morning-after pill when obtaining emergency contraception, probably due to the convenience of visiting a pharmacy. The IUD must be fitted by a health professional at a GP surgery or a sexual health service.