Blood clot risk varies by hormonal contraception type used, personalized counseling needed
Key takeaways:
- VTE risk among women varied based on the type of hormonal contraceptive they used.
- These trends persisted regardless of BMI, smoking or family history.
A woman’s risk for blood clots varied by the type of hormonal contraception used, according to a nationwide cohort study conducted in Denmark.
Rates of venous thromboembolism appeared highest among women who used hormonal contraceptives that contained third-generation progestins, as well as those who used combined pills.
Data showed no elevated VTE risk among women who used intrauterine devices (IUDs).
“Hormonal contraception is widely used, and while the risk for venous blood clots with hormonal contraceptives is well known, newer formulations — such as those containing low-dose estrogen, novel progestins and bioidentical estrogen — have not been as thoroughly evaluated in large population-based studies,” Harman Yonis, MD, PhD, of the department of emergency medicine at Aalborg University Hospital in Denmark, told Healio. “Our goal was to update the risk profile for all available contraceptive types to help physicians and patients make more informed decisions.”
Hormonal contraception is recognized as a risk factor for VTE.
Yonis and colleagues used national registers in Denmark to evaluate VTE risk based on types of contemporary hormonal contraceptives used.
The analysis included data from 1,397,235 women aged 15 to 49 years with no history of cancer, thrombosis, thrombophilia, liver or kidney disease, hormone therapy, infertility treatment, oophorectomy, hysterectomy, endometriosis or polycystic ovary syndrome.
Follow-up began on Jan. 1, 2011, or a person’s 15th birthday, and it continued until July 1, 2021, emigration, death or an exclusionary event.
Diagnosis of lower-limb deep VTE or pulmonary embolism served as the main outcome.
Researchers identified 2,691 VTE events over 8,455,601 person-years of follow-up.
Investigators calculated the following standardized VTE rates per every 10,000 person-years: 11.9 cases (95% CI, 4.4-25.6) for injections, 10 cases (95% CI, 9.2-10.9) for combined pills, 8.1 cases (95% CI, 1.5-25.1) for patches, 8 cases (95% CI, 4.6-12.8) for vaginal rings, 3.6 cases (95% CI, 2.8-4.7) for progestin-only pills, 3.4 cases (95% CI, 1.7-6.3) for implants, 2.1 cases (95% CI, 1.7-2.6) for IUDs and 2 cases (95% CI, 1.9-2.1) for nonuse.
Compared with nonuse, researchers calculated VTE rate ratios of 5.7 (95% CI, 3.5-9.3) for injections, 5 (95% CI, 2.1-12) for patches, 4.6 (95% CI, 4.2-5) for combined pills, 4.5 (95% CI, 3.1-6.5) for vaginal rings, 2.4 (95% CI, 1.4-4) for implants, 1.8 (95% CI, 1.4-2.3) for progestin-only pills and 1 (95% CI, 0.8-1.1) for IUDs.
Corresponding additional VTEs per every 10,000 person-years included 9.9 (95% CI, 0.5-19.3) for injections, 8 (95% CI, 7.2-8.7) for combined pills vs. nonuse, 6.1 (95% CI, 3.6 to 15.8) for patches, 6 (95% CI, 2.1-9.8) for vaginal rings, 1.6 (95% CI, 0.7-2.6) for progestin-only pills, 1.4 (95% CI, 0.7 to 3.5) for implants and 0.1 (95% CI, 0.3 to 0.6) for IUDs.
These associations remained consistent regardless of BMI, smoking or family history.
“The overall findings were consistent with earlier research, showing that combined hormonal contraceptives increase the risk for venous blood clots,” Yonis told Healio. “What stood out was the variation in risk between different types of contraceptives. We were also reassured to find that hormonal IUDs with levonorgestrel were not linked to an increased risk for venous blood clots, making them a safer alternative for women concerned about this issue.”
Researchers acknowledged study limitations, including possible residual confounding factors. The study population’s homogeneity and health profile may limit generalizability, they added.
The findings highlight the need for “personalized contraceptive counseling,” Yonis and colleagues wrote.
“It’s important to emphasize that while the risk for venous blood clots exists, these events are rare,” Yonis told Healio. “Hormonal contraception offers many benefits beyond birth control, such as helping manage menstrual problems and reducing the risk for certain cancers. The goal is not to discourage its use but to promote informed and personalized choices.
“Future research should confirm these findings in more racially and ethnically diverse populations, and explore how personal factors like genetics and lifestyle influence the risk for venous blood clots with hormonal contraception,” he added. “It would also be valuable to study long-term outcomes beyond the first diagnosis of a venous blood clot, such as recurrence or chronic complications.”
For More Information:
Harman Yonis, MD, PhD, can be reached at harman@live.dk.
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