These findings may help guide contraception use before surgery.
Women’s risk of developing thrombosis returns to normal within four weeks of stopping combined hormonal contraception, research suggests.
Swiss researchers said the finding may help manage patients taking combined hormonal contraceptives before major surgery.
“Combined hormonal contraceptive cessation is followed by a rapid decrease in estrogen-related thrombotic biomarkers,” they wrote in Blood.
“Two to four weeks of cessation prior to planned major surgery, or withdrawal of anticoagulants in venous thromboembolism patients, appears sufficient for the majority of women.”
The study included 66 women with an average age of 27 who were taking oral, vaginal or transdermic estro-progestative contraception such as birth control pills, vaginal rings and transcutaneous patches.
Researchers measured serum coagulation markers – protein C and thrombodulin – at baseline (prior to stopping the combined hormonal contraceptives) and then again at weeks one, two, four, six and 12, comparing them to 28 controls not taking hormonal contraception.
The researchers found the coagulation markers dropped by around 80% within one to two weeks after stopping the hormonal birth control. By week 12, levels were similar to the control group.
“We found that the majority of the elevation of estrogen-induced haemostatic biomarkers decreased within two to four weeks after combined hormonal contraceptives stop,” the researchers said.
Co-author and vascular medicine expert Dr Marc Blondon said the findings could help inform discussions around whether combined hormonal contraceptives were right for each patient, and patient-surgeon discussions of whether the benefit of stopping for a short time exceeded the risks.
“It’s very important to talk about the benefits of contraception because it’s crucial to avoid unwanted pregnancy and for women to have the choice of a planned pregnancy,” said Dr Blondon, from the University Hospitals of Geneva.
“It’s reassuring to know that that possible harm of the pill goes away rapidly when one stops taking it.”
Dr Blondon added that the study used biomarkers as a marker of clotting risk, and said more research was needed to confirm whether that translated to a reduction in clotting events.
The researchers said women taking combined hormonal contraceptives had a three-fold increased incidence of venous thromboembolism, and hormonal contraceptive-associated thrombosis represented almost half of the venous thromboembolism events in women of reproductive age.
It was well-known that exogenous estrogens needed to be stopped after a venous thromboembolism event, they said. But there was a trend to not stop contraception in the aim of decreasing the risks of unwanted pregnancies and abnormal uterine bleeding, and to continue contraception for some time during the anticoagulation period.
“Based on our study, stopping combined hormonal contraceptives two to four weeks prior to the planned day of cessation of anticoagulation may be safe in most women.”
The researchers said guidelines around taking – or ceasing – combined hormonal contraceptives before surgery varied from country to country. The World Health Organization only recommended that contraceptives were stopped before major surgery, without a timeframe, they said.
“Our data showing a fast decrease of the estrogen-related thrombotic biomarkers suggest that, if the decision to stop combined hormonal contraceptives perioperatively is made, a short-term (two to four weeks) preoperative cessation is enough in most patients.”
Most of the participants were young, Caucasian and had a healthy weight, but the researchers said their subgroup analyses did not suggest that the results would be different in older women, different racial groups or people who were overweight.