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Blood Clots and the Birth Control Patch


I am almost 35 and a bit overweight so I'm concerned about blood clots with The Pill. My doctor thought that the patch called Evra would be safer, but I found some stuff on the Internet about lawsuits because Evra increases blood clots. What do you think?


Thanks for your question. The issues around the first ever contraceptive patch and blood clots are complex. It is ironic that there are warnings about blood clot risks using a transdermal form of hormonal contraceptive that should cause less risk than the usual contraceptive pill. Let's see if I can sort out some of the confusion for you and give you information that will help you make your decision.

First of all, you are to be complimented for knowing that being older (in the premenopausal scheme of things) and being overweight or obese increase your risk for blood clots. The other thing that also increases the risk for clots or cardiovascular disease is smoking cigarettes. Finally, your risk is markedly increased if you've ever had a blood clot in a vein your leg (often called thrombophlebitis).

Clots and hormonal contraception

I'm also pleased that you are aware of the possibility of clots related to hormonal contraception. You are quite right to be concerned for, although the risks are low for a woman of your age, the consequences can be very serious if a blood clot goes to the lungs (called pulmonary embolism), forms in the brain (stroke) or in a coronary artery (called a heart attack). The bottom line is that high dose estrogen causes blood clots. Although we call it "low dose," even today's Pill has four to five times higher estrogen than natural, menstrual cycle estrogen levels.

Clot risks with estrogen through the skin versus by mouth

The risk for clots with high estrogen is true whether that estrogen enters the general circulation directly after being produced by the ovaries as happens occasionally during the menstrual cycle, as is common in perimenopause, or is produced by the placenta as occurs in pregnancy. But that risk of clots from high estrogen production that goes directly into the blood stream is far less than the risk from estrogen by mouth that is absorbed from the stomach into blood vessels that first go to the liver before reaching the general circulation. The reason is that the liver rapidly starts making blood clotting proteins that increase the risk for thrombosis. Our best evidence for the decrease by at least half of estrogen that goes directly into the blood stream (as is the case with all transdermal (meaning trans = through, and dermal = skin) forms such as patches, gels and creams, comes from some large comparison studies of rates of blood clots with menopausal transdermal estrogen versus pill estrogen.

The contraceptive patch controversy - too little data

Now to the controversy about the Evra® contraceptive patch - there are two different estrogen doses of a patch with almost the same name. The Ortho Evra® contraceptive patch marketed in the USA contains 75 μg of ethinyl estradiol while the Evra® patch marketed in Canada contains 60 μg of ethinyl estradiol. The significantly lower dose of estrogen in the Canadian patch has been shown to deliver similar levels of estrogen as the usual Pill forms of "low dose" oral contraceptive.

Another important fact is that, when a safer kind of contraception (or any therapy) is announced, doctors tend to prescribe it for women at higher risk. Therefore, it is likely that women with greater risks for blood clots were preferentially prescribed Evra® or Ortho Evra®. In the USA, when women experienced blood clots on OrthoEvra® and didn't expect them, they brought a lawsuit. To be safe from suit, Canada's Health Protection Branch basically is saying that Evra® and Ortho Evra® are the same in terms of risks for blood clots although is not likely true given how much higher the estrogen doses are in the one marketed in the USA.

A couple of studies have looked at the risks for blood clots on a bunch of different kinds of oral contraceptives versus the contraceptive patch. One study that is not published, that was funded by a company that makes a different Pill and is a rival of the one making the patch contraceptive found results that were highly variable but suggested that clot risks are higher on the patch. Another study, that is published and is apparently without the same pharmaceutical risks, showed a very clear result that the risks for clots did not differ. Before we will know the truth about clot risks on Evra compared with the Pill, a randomized comparative study will need to be done.

Contraceptive choices for midlife women

Now back to you and your contraceptive choices. I think the most reasonable and safe way for you to prevent pregnancy is to stop hormonal contraception and concentrate on barrier methods (condom, diaphragm or female condom) plus spermicidal jelly. That is as effective as hormonal methods, will carry no risks for blood clots, and will not alter your cycles and experiences so that you'll know when you start into perimenopause, the transition to menopause. There is an article on the CeMCOR website called "Choices for Effective Contraceptives" that will discuss this idea more thoroughly. For sure, I think it is risky to be on a hormonal form of contraception during perimenopause when your own estrogen production becomes higher and erratic, the high estrogen/progestin in the contraception won't reliably suppress your own levels with the potential to experience extremely and risky excess estrogen.

Hope this is helpful for you.

All the best,


Updated Date: 
Tuesday, November 19, 2013 - 13:15

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