Side Effects of Combined Hormonal Contraceptives Carry Higher Blood Clot Risks Than Others: Study

The Depo-Provera birth control shot carried the highest risk of life-threatening blood clots among all forms of birth control, researchers found.

Doctors have long warned women that hormonal birth control can increase the risk of a serious type of blood clot, known as venous thromboembolism (VTE), which are further supported by the findings of a recent study, which suggests that the risk also applies to newer birth control drugs.

The research, published in the Journal of the American Medical Association (JAMA) on February 10, indicates that birth control injections, like Depo-Provera, and patches like Xulane and Twirla, carry the highest risk of blood clots along with combined birth control pills, especially those with third-generation hormone formulations.

Venous thromboembolism is a serious condition where a blood clot forms deep in the veins of the legs or arms, requiring immediate treatment to prevent it from breaking off and traveling to the lungs, potentially causing a life-threatening pulmonary embolism.

Birth Control Blood Clot Risks

Health experts have long known that hormonal birth control pills carry a risk of causing a VTE, especially among women with other risk factors like smoking and obesity. However, little research has been done on newer formulations of birth control hormones.

In this new study, Danish researchers analyzed the use of combined hormonal pills with estrogen and progestin, progestin only pills, the vaginal ring, the patch, intrauterine devices (IUDs), implants and injections. They analyzed data for 1.4 million women from Danish national registers from 2011 to 2021, including women 15 to 49 years old without a history of blood clots, cancer, liver or kidney disease, and other reproductive health conditions.

The data indicated a total of 2,600 blood clots occurred in women during the study period. Those taking combined birth control pills suffered 10 VTEs per 10,000 person-years compared to women taking no type of birth control. Comparatively, eight blood clots per 10,000 years for women using vaginal rings or the patch, 12 for those who received the Depo-Provera shot, three for progestin-only pills, three for implants, and two among IUD users per 10,000 person years.

Overall, the risk of blood clots was the highest when taking combined birth control pills or receiving the injection, like Depo-Provera. Using a patch like Xulane, combined hormone birth control pills, and vaginal rings like NuvaRing also carried a high risk of VTE.

Combined hormone birth control pill brands include Ortho Tri-Cyclen Lo, Katya, Femodene, Gedarel and Millinette 20.

However, using a progestin-only pill, like Nora-Be, Slynd and Opill, or an IUD like Kyleena, Skyla and the Paragard IUD, carried the lowest risk of VTE, with Paragard carrying no additional increased risk of VTE, when compared to not using hormonal contraceptives at all.

Researchers concluded that the data could help doctors provide patients with the best information about the risks and benefits of different types of birth control, which could be of particular use to those who already face an increased risk of blood clots due to other factors.

Depo-Provera Lawsuits

The findings come as Pfizer and some generic drug manufacturers face an increasing number of Depo-Provera lawsuits, which claim that the quarterly injections increase the risk of brain tumors.

Earlier this month, about 70 such lawsuits were consolidated for coordinated pretrial proceedings in the U.S. District Court for the Northern District of Florida before U.S. District Judge Casey Rodgers as a Depo-Provera multidistrict litigation, or MDL. That number is expected to continue to climb in the coming months and years.

Now that the Depo-Provera lawsuits have been consolidated into an MDL, all current and future claims brought in any federal court will be transferred to Judge Rodgers for coordinated discovery, pretrial motions and potentially a series of early bellwether test trials.

However, if the parties fail to reach a Depo-Provera MDL settlement or another resolution after all pretrial proceedings are concluded, each individual lawsuit may later be remanded back to the U.S. District Court where it was initially filed for an individual trial in the future.