SRISUPA LAOPAKORN, M.D.
Gynecologic Oncology Gynecologic Laparoscopic Surgery Sexual Medicine
First, let us understand venous blood clots. Venous Thromboembolism (VTE) is a condition where blood clots form in veins, which can occur in superficial veins (Superficial vein) or deep veins (Deep vein).
Deep Vein Thrombosis (DVT) is a condition where blood clots form in the deep veins of the body, potentially at a single site or multiple sites, most commonly in the legs. Acute cases present with leg swelling, redness, and pain. It is considered a dangerous condition because the obstructing clot can break loose and travel through the bloodstream to block pulmonary veins (Pulmonary embolism: PE), which has a high mortality rate.
Illustration showing deep vein thrombosis in the leg and its circulation causing pulmonary embolism
Image courtesy of: https://www.chelwest.nhs.uk/your-visit/patient-leaflets/support-services/are-you-at-risk-of-blood-clots-dvt-deep-vein-thrombosis-and-pe-pulmonary-embolism
The birth control pills referred to here are oral combined hormonal contraceptives containing Estrogen (Estrogen) and Progestin (Progestin). Check the package or blister pack being used; they are classified by estrogen levels. High-dose estrogen (≥ 50 mcg) poses a higher risk of blood clots than low-dose estrogen (≤ 35 mcg)) due to mechanisms related to the increase and decrease of blood clotting factors.
Progestin is further divided into 4 generations, and each generation used in combined hormonal contraceptives containing estrogen carries a different level of blood clot risk.
Other types of contraceptives containing progestin only include:
For combined hormonal patches or contraceptive rings, clear data regarding VTE risk is still lacking, unlike combined oral contraceptives (COCs), which carry a venous thromboembolism risk comparable across combined hormonal formulations.
In summary, current data indicates that combined hormonal contraceptives increase the risk of venous thromboembolism to 3–9 cases per 10,000 users, compared to 1–5 cases per 10,000 non-pregnant non-users (ACOG committee opinion No.540 November 2012), representing a 2 to 5-fold increase. This depends on the estrogen dose and progestogen type in the combined formulation, with the highest risk occurring in the first few months of starting the medication.
Pregnant women and those up to 12 weeks postpartum face up to a 12-fold increased risk (48-60/10,000), which is significantly higher than that of combined oral contraceptive use.
Table showing the risk of venous thromboembolism categorized by estrogen dose and progestin type in combined contraceptives compared to non-users (The relative risk of venous thromboembolism in current users of different types of hormonal contraception according to estrogen dose, progestin type and route of administration. Nonusers reference group)1
Image courtesy of: Lidegaard, Øjvind. (2014). Hormonal contraception, thrombosis, and age. Expert opinion on drug safety. 13. 1353-60.
As for Visanne, which contains only progestogen Dienogest 2mg used to treat endometriosis, there is currently no clear data regarding increased risk for venous thromboembolism.
However, do not be overly concerned about combined hormonal contraceptives and venous thromboembolism (VTE), as they offer numerous benefits beyond contraception. These include treating endometriosis, dysmenorrhea (painful periods), hypermenorrhea (heavy menstrual bleeding), irregular bleeding, and polycystic ovary syndrome (PCOS). They also treat symptoms of excess androgen such as acne, hirsutism, and oily skin, while helping to reduce the risk of colorectal, ovarian, and endometrial cancers.
Therefore, taking birth control pills for contraception or treatment correctly, appropriately, and under regular monitoring will ensure safety from side effects. Doctors or pharmacists will provide advice, assess underlying risk factors, check for contraindications before starting, and guide monitoring. Women taking birth control pills should maintain good health, observe symptoms and side effects, and reduce other risk factors that increase VTE risk, such as weight management and smoking cessation.
Illustration showing causes and risk factors of deep vein thrombosis (Causes and Risk Factors of Deep Vein Thrombosis)2 Image courtesy of: By Dawn Stacey, PhD, LMHC Medically reviewed by Scott Sundick, MD on March 03, 2021
Based on this data, the MHRA (Medicines & Healthcare products Regulatory Agency) concluded that COVID-19 vaccination remains safe and highly beneficial in preventing infection. Rare side effects involving blood clots with low platelets continue to be monitored.
Currently, there is no clear evidence of a link between the two, and the mechanisms of clot formation from combined hormonal contraceptives and vaccination are different. Pregnant women, who have a higher VTE risk than birth control users, are also recommended to get vaccinated according to reference guidelines6-9.
Based on current data, individuals using any type of hormonal contraceptive can receive the COVID-19 vaccine without needing to discontinue their medication, as no increased risk of venous thromboembolism has been found. Pregnant women past 12 weeks of gestation or breastfeeding mothers can also receive the COVID-19 vaccine, evaluated based on risk levels and underlying health conditions.
Individuals using any type of hormonal contraceptive can receive the COVID-19 vaccine without needing to discontinue their medication, as no increased risk of venous thromboembolism has been found.
Gynecologic Oncology Gynecologic Laparoscopic Surgery Sexual Medicine
