French researchers and colleagues report that the elevated risk essentially goes away within 2 to 4 weeks after the use of the pills ends. Their results are published in the journal Blood.
The authors suggested that their findings can help determine the best time to cease oral contraceptives before events that could further increase the risk of dangerous clots, such as major surgery, prolonged periods of immobility, or when tapering anticoagulant medications after a blood clot (DVT or pulmonary embolism).
Background information in the article pointed out that combined hormonal contraceptives (CHCs) are known to increase the risk of blood clots, affecting roughly 10 in 10,000 women on estrogen-containing birth control, according to the CDC.
“Our goal was not to look at the thrombotic risk of contraceptives, but to determine how long that risk takes to normalize after stopping contraceptives,” explained corresponding author Marc Blondon, MD, an expert in vascular medicine at the University Hospitals of Geneva, Switzerland. “It’s reassuring to know that that possible harm of the pill goes away rapidly when one stops taking it.”
Essentially, the study found that most of the resistance to protein C and thrombomodulin disappears within 2 to 4 weeks after cessation of combined hormonal contraceptives. Previous to the study, the persistence of the risk of venous thromboembolism (VTE) due to CHCs after their cessation, was unknown.
To help guide clinical practice, the researchers write that their goal in the prospective cohort study was to define the time until normalization of the estrogen-related thrombotic biomarkers after CHC cessation. The participants were adult women up aged to 50 years who had decided to stop their CHC, excluding those with a personal history of VTE, current anticoagulation, a recent medical event, or pregnancy.
The study began prior to cessation of CHC, with six visits afterwards (at 1, 2, 4, and 6-12 weeks post cessation). The primary outcomes were defined as normalized sensitivity ratios to activated protein C (nAPCsr) and to thrombomodulin (nTMsr), with sex hormone–binding globulin (SHBG) as a secondary end point.
Women without CHC use were included as controls. “Among 66 users of CHC, from baseline until 12 weeks average levels of nAPCsr, nTMsr, and SHBG decreased from 4.11 (SD2.06), 2.53 (SD1.03) and 167 nmol/L (SD103) to 1.27 (SD0.82), 1.11 (0.58) and 55.4nmol/L (SD26.7), respectively,” the authors wrote. “On a relative scale, 85.8%, 81.3% and 76.2% of the decrease from baseline until 12 weeks was achieved at 2 weeks, and 86.7%, 85.5% and 87.8% at 4 weeks after CHC cessation, respectively.”
They added that levels were not meaningfully modified throughout the study period among 28 control women.
“In conclusion, CHC cessation is followed by a rapid decrease in estrogen-related thrombotic biomarkers,” the study noted. “Two to four weeks of cessation prior to planned major surgery, or withdrawal of anticoagulants in VTE patients, appears sufficient for the majority of women.”
“These findings can help to inform discussions around whether combined hormonal contraceptives are right for the patient, as well as patient-surgeon discussion of whether the benefit of stopping for a short time actually exceeds the risks,” Dr. Blondon said. “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.”
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