Overweight and progestogen-only contraceptive pills
This question has been received on numerous occasions by the NLH Q&A Service. Our 'standard' answer is:
The Faculty of Family Practice and Reproductive Health Care recently answered a closely related question – ‘Should women who weigh >70kg who use progestogen-only pills take two pills per day to improve contraceptive efficacy?’ , their answer is:
"FFPRHC CEU guidance states that it has been practice for some health professionals in the UK to advise women who weigh >70kg using POPs containing levonorgestrel, norethisterone or etynodiol diacetate to take two pills together every day. Direct evidence to support this however was not identified. Indirect evidence from studies show that obese women who use levonorgestrel implants or vaginal rings have higher failure rates than non-obese women. For women using the etonorgestrel-only implant anovulation occurs in 100% of women. The levonorgestrel-only implant is less reliable in ovulation inhibition especially in the first years of use. Data may be extrapolated to effect on weight and POPs containing levonorgestrel, norethisterone and etynodiol diacetate which are also less reliable at ovulation inhibition. The desogestrel-only pill reliably inhibits ovulation in 97% of cycles and does not appear to be influenced by weight.
No evidence was identified that taking two POPs per day is harmful and until further direct evidence is available the CEU continues to advise that women >70Kg using POPs containing levonorgestrel, norethisterone, etynodiol diacetate should be advised to take two pills together every day (unlicensed). Women using the desogestrel-only pill are advised to take only one per day regardless of weight."
PRODIGY, in their guideline on contraception  report:
"The effect on BMI and weight on the risk of pregnancy while using oral contraceptives (ethinylestradiol 35 micrograms or less, multiphasic COC, and progestogen-only) has been investigated in a recently published case-control study
- The absolute risk of pregnancy was found to increase in women having a BMI greater than 27.3 suggesting a possible reduction in efficacy of hormonal contraception.
- However the evidence available is not strong enough to support a change in current practice. Note: the option to explore using additional or alternative contraceptive methods should be discussed with overweight women."
- 1) FFPRHC. Should women who weigh >70kg who use progestogen-only pills take two pills per day to improve contraceptive efficacy? 2006 (http://www.ffprhc.org.uk/admin/uploads/No1491.pdf)
- 2) PRODIGY. Contraception. 2005 (http://www.prodigy.nhs.uk/contraception/view_whole_guidance)