Continuing our discussion from last week about birth control and obesity (OK, sort of about birth control and obesity, sort of about truth in headlines…), there are new data out this week in the current edition of ACOG’s green journal. This study, also a randomized, controlled clinical trial — the highest form of clinical evidence — found that, among the nearly 200 study participants, normal-weight and obese women taking oral contraceptive pills (OCPs) consistently had the same risk of ovulation. As the study authors wrote, “normal-weight and obese participants who were consistent OCP users experienced substantial and comparable ovarian suppression during OCP use.”

One thing I have loved in the news coverage this week, however, was study author Dr. Carolyn Westhoff’s commentary on the risks of prescribing higher dose (and supposedly more reliable?) birth control pills to obese patients. As Reuters — not even a medical industry news source! how rad! — reported:

“The new findings, along with more recent clinical trials, should put to rest concerns that obese women are more likely to get pregnant while on the pill, Westhoff says. The issue has confounded doctors, she notes, because some companies have pushed physicians to prescribe higher dose formulations to their obese patients based on the idea that lower doses aren’t effective.”

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The problem with this approach, she explains, is that obese women are at increased risk of developing life-threatening blood clots in their veins. Taking the pill-especially at higher doses-further increases the risk these clots will occur.

That’s right. While higher-dose pills probably don’t increase efficacy, they do increase the risk of deep vein thrombosis and other cardiovascular complications. Important to note is the fact that “high-dose” and “low-dose” often refer to the amount of estrogen in the Pill. And while estrogen can do wonders to regulate periods, it’s the progestin component that gives the Pill most of its power to protect against pregnancy. So, especially for obese women who smoke or have a strong family history of cardiac problems or are older than age 35, low-dose is better, and progestin-only may be best.  

As the reproductive-age population continues to have high rates of obesity, birth control efficacy will continue to be an issue for investigation and discussion. But it’s important to remember that birth control risk will and should continue to be an issue for us to discuss amongst ourselves and with our patients.