Warning over effectiveness of morning-after pill for overweight women

More than half of women who take the morning-after pill could still fall pregnant because they are overweight, experts have warned.

Emergency contraception providers have been advised to tell women who are overweight according to their BMI or weigh more than 11st that it is possible the drug will not work.

New guidelines issued by the Faculty of Sexual and Reproductive Healthcare (FSRH), part of the Royal College of Obstetricians and Gynaecologists, raise concerns over the two most commonly prescribed morning-after pills, levonorgestrel and ulipristal acetate, known as Levonelle or ellaOne.

Researchers found that having a BMI of more than 26 particularly affected the effectiveness of Levonelle, which has to be taken within 72 hours of having unprotected sex.

The report said: "Women should be informed that it is possible that higher weight or BMI could reduce the effectiveness of oral emergency contraception, particularly levonorgestrel for emergency contraception. Women should be informed that the effectiveness of the copper IUD is not known to be affected by weight or BMI."

Double dosing of the morning-after pill is not usually advised, but the guidelines say doctors should consider prescribing twice the dose of Levonelle if a patient is overweight.

The FSRH advises that a copper intrauterine device, known as an IUD or coil, is the most effective form of emergency contraception.

However it warned a recent survey of women aged 18-45 found "worrying gaps" in knowledge about the most effective methods of emergency contraception.

Around one in 10 women could identify the most effective form of emergency contraception, the copper coil. Nearly two-thirds incorrectly believed the morning-after pill was most effective.

Dr Asha Kasliwal, FSRH president, said: "The guideline's emphasis on the efficacy of the copper intrauterine device as emergency contraception and ongoing contraception reinforces existing Nice (National Institute for Health and Care Excellence) guidance on this issue and we hope its publication will further awareness amongst healthcare professionals and women alike that the copper IUD is the most effective form of emergency contraception."

Figures released by the NHS this week showed that in 2015 around 60% of women in England were classed as overweight or obese, meaning their BMI was higher than 25.