When it comes to birth control, there’s often talk about whether having a higher body weight makes contraception less effective. If you’ve ever wondered whether your BMI could affect your birth control, you’re not alone. It’s a question that’s been around for a long time, and thanks to recent research, we’re finally getting clearer answers.
For many years, individuals perceived that individuals who had obesity were more likely to have failed birth control and therefore an unplanned pregnancy. That concept may initially appear baffling, particularly because obesity has also been associated with increased infertility due to hormonal alterations that can impact ovulation and menstrual cycles. How can both be the case? As it happens, the body weight-birth control connection isn’t so straightforward as once believed.
Here’s why some assumed that body weight could affect birth control efficacy. Some researchers suggested that a greater proportion of body fat may alter how the body absorbs, metabolizes, and distributes the hormones in contraceptive drugs. Factors such as expanded blood volume or quicker digestion may come into play, or proteins in the blood may influence how much of the hormone is active. But when scientists tested these hypotheses in real-world situations, the findings were generally reassuring.
Large studies have determined that for the great majority of hormonal contraceptives, effectiveness does not drastically differ by BMI. For instance, scientists at Columbia University Medical Center examined obese women who took the birth control pill. They discovered that when taken daily, the pill suppressed ovulation just as effectively in women with higher BMIs as it did in women with lower BMIs. In other words, it wasn’t weight—it was whether or not the pill was being taken daily.
Considering the variety of hormonal contraceptives available, the majority are well-suited for individuals with greater body weight. These are the combined pill, the vaginal ring, and the Depo-Provera injection. Although hormone levels in the bloodstream might be somewhat lower in women with obesity, the levels remain high enough to suppress ovulation and pregnancy.
One exception is the patch. Clinical trials for the contraceptive patch (such as Xulane or Ortho Evra) determined that it may be less effective in individuals who weigh more than 198 pounds (approximately 90 kilograms). In those trials, most of the pregnancies that were reported occurred in that heavier group, although they represented a smaller percentage of study subjects. For this reason, the patch is usually not the initial advice for individuals with a higher BMI.
The other essential consideration is overall health and the likelihood of blood clots, or venous thromboembolism (VTE). Obesity alone enhances the chance of VTE, and throwing estrogen-containing forms of birth control—such as the pill, patch, or ring—into the mix can increase that risk slightly. All that being said, it’s worth noting that the risk of VTE during pregnancy is higher than when taking these contraceptives. Low-dose pills of today have less risk than previous generations, and for most individuals, the overall risk is low.
However, if you have other chronic illnesses such as high blood pressure, diabetes, or a family or personal history of blood clots, it’s worth discussing in great detail with your healthcare provider.
It’s also worth clearing up a common myth: hormonal birth control does not consistently cause weight gain, regardless of your size. While some people may notice slight weight changes, large studies haven’t found a significant or predictable connection between hormonal contraception and weight gain.
So what’s the message if you are at a higher BMI and looking into birth control? The key is consistency. Taking your birth control precisely as prescribed is much more vital than weight when it comes to avoiding pregnancy. If you are worried about the patch’s reliability, you have plenty of excellent options—the pill, the ring, the shot, or an IUD are all good choices for individuals of any size.
And if you’re concerned about blood clots or other complications, don’t be afraid to discuss it with your healthcare provider. They can guide you through taking your overall health into account and selecting the safest and most effective method for your lifestyle. There’s no single answer that fits everyone, but with the right information and advice, you can have faith in making what’s best for you.
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