Study confirms some contraceptive pills more likely to cause blood clots

A study published in the British Medical Journal today confirms previous findings that certain oral contraceptive pills are more likely to cause serious blood clots (venous thromboembolism - VTE ) than others.

The authors, led by Dr Øjvind Lidegaard from the University of Copenhagen, say that women on pills containing one of the newer types of progestogen hormone (drospirenone, desogestrel or gestodene) have double the risk of VTE than women on pills containing an older progestogen (levonorgestrel).

Previous studies have indicated that the new types of progestogen hormone might increase the risk of VTE. So Lidegaard and colleagues carried out a large-scale study to assess the risk of VTE for women using with different progestogens.

The researchers reviewed data of the hormonal contraception patterns and first time VTE episodes for all Danish non-pregnant women between the ages of 15 and 49 from January 2001 until December 2009.

The participants had no previous record of either or cancer before the study began.

The research team assessed over eight million women years of observation and during this period there were 4,246 first episodes of VTE.

The relative risk of VTE whilst taking the oral contraceptive pill is still low, explain the authors. Compared with non-users of hormonal contraception, pills with levonorgestrel increase the risk of VTE threefold and pills with drospirenone, desogestrel or gestodene increase the risk sixfold.

In absolute terms, the risk of VTE in current users of newer is about 10 per 10,000 women years. This means that about 2,000 should shift from using oral contraceptives with desogestrel, gestodene, or drospirenone to those with levonorgestrel to prevent one event of VTE in one year, say the authors.

The increased risk remained even after taking account of other possible causes for VTE, they conclude.

In an accompanying editorial, Dr Philip Hannaford from the University of Aberdeen says "it is difficult not to conclude that combined oral contraceptives with desogestrel, gestodene or drospirenone confer a higher risk of venous thromboembolism than those with levonorgestrel" and that "many clinicians will choose to minimize the risk by prescribing a combined oral contraceptive with levonorgestrel whenever possible."

Hannaford stresses however that it is crucial "not to exaggerate the risk - oral contraceptives are remarkably safe and may confer important long term benefits in relations to cancer and mortality."

add to favorites email to friend print save as pdf

Related Stories

Risk of blood clots in veins hereditary

May 31, 2011

Venous thromboembolism (VTE) is the third most common type of cardiovascular disease after coronary heart disease and stroke. Researchers at the Centre for Primary Health Care Research in Malmo have mapped the significance ...

US reviews birth control pill safety over clot risk

May 31, 2011

The US Food and Drug Administration said Tuesday it is reviewing recently published studies which have pointed to an increased blood clot risk associated with a certain type of birth control pill.

Recommended for you

Seniors successfully withdraw from meds

Sep 19, 2014

Elderly people have proved receptive to being de-prescribed medications, as part of a trial aimed at assessing the feasibility of withdrawal of medications among older people.

Flu vaccine for expectant moms a top priority

Sep 18, 2014

Only about half of all pregnant women in the U.S. get a flu shot each season, leaving thousands of moms-to-be and their babies at increased risk of serious illness.

Experts want restrictions on testosterone drug use (Update)

Sep 17, 2014

Federal health experts said Wednesday there is little evidence that testosterone-boosting drugs are effective for treating common signs of aging in men and that their use should be narrowed to exclude millions of Americans ...

User comments