Google NuvaRing (a contraceptive vaginal ring changed monthly) and the top of the page will almost certainly have one (or more) advertisements from malpractice attorneys looking to sue the manufacturer and probably the doctor who prescribed it.
While the links in this shaded area are advertisements and don’t necessarily reflect, ahem, high-quality medical information, there has been murmurings for a few years over the NuvaRing and a possible increased risk of blood clots above and beyond the risk imparted by the standard birth control pill.
There are a couple of ways NuvaRing could increase the risk of blood clots: blood levels of hormones are higher with vaginal delivery compared with a pill and one of the hormones in the ring, etonogestrel, is closely related to desogestrel and birth control pills with this hormone do have a higher risk of blood clots. But just because it’s biologically plausible doesn’t mean it’s true.
So what does the latest medical research tell us? A recent study in the BMJ (Lidegard et al 2012) tells us that if 10,000 women are followed for one year:
- 2.1 women not using any hormonal birth control will have a clot
- 6.2 users of the regular birth control pill will have a clot
- 7.8 NuvaRing users will have a blood clot.
One weakness of this study is that it looked at medical records and there was no data about other risk factors for blood clots (obesity, for example), but a big strength is that a very large number of women were studied (the equivalent of 9 million women over one year).
Another study (Dinger J et al) followed 33,000 women in a prospective study, so higher a quality design because other factors that increase the risk of blood clots were factored in. This study tells us that the risk of a blood clot is essentially the same with the pill and the NuvaRing; however, there are a few issues with this study:
- It’s still unpublished (presented at a meeting but as of yet has not seen print)
- Was funded by the manufacturer
- The abstract doesn’t tell us how many of the birth control pill users were on pills with a higher risk of blood clots (such as Desogen, Mircette, or Yaz) and how many were on a regular lower-risk pill. Whether the NuvaRing has the same clotting risk as the higher risk or the lower risk pills makes a difference.
When faced with conflicting studies (as an aside, if you really to see conflict check out the comments section for the Lidegard study in the BMJ, some of these contraception researchers appear to despise each other’s scientific methods) it’s probably best to assume the highest risk, understanding that it may be an over estimation.
Taking that approach it appears that an additional 1 to 2 women for every 10,000 who use the NuvaRing for a year may be risking a blood clot.
What should you do with this information?
It is important to individualize medical care. For women who have been pregnant due to birth control pill failure, have side effects with the birth control pill that they don’t get from the ring, have trouble remembering to take a pill, or have a medical condition that is specifically improved by the NuvaRing the potential increased risk might be worth it. Women who have never had an issue with the pill may feel differently and women with a higher risk of blood clots may wish to stay away from the ring until there’s more information.
But ultimately risk is perceived very differently by different people. Some people will feel a blood clot risk of 1-2/10,000 per year (or 0.01%-0.02%) is high and others will think it’s low. For comparison, the risk of dying in a motor vehicle accident in the United States is 1.6 per 10,000 licensed drivers per year (or 0.0016%). It is also important to remember that it is medical safer to be on the pill or to use the ring than to be pregnant.
Just don’t get me started on the risks of making medical decisions based on information provided by a malpractice attorney.
Remember, this post does not represent individual medical advice.