Birth control pills, implants, and intrauterine devices (IUDs) are highly effective at preventing pregnancy, but people in larger bodies may have different experiences with birth control than those in smaller bodies.

Studies show that women with higher body fat levels have an increased risk of many birth control-related side effects. Plus, certain forms of birth control, like emergency contraception and birth control patches, may not be as effective for women with obesity.

This article discusses the effects of obesity on birth control side effects, safety, and efficacy.

Although you may have heard that many birth control methods are less effective if you have obesity, that’s actually not the case.

According to a 2018 review, most methods of birth control are effective for women with obesity, except the birth control patch and emergency contraceptive pills.

We’ll dive into more details about different types of birth control later in the article, but first, it’s important to note that women who are considered to have obesity are at a higher risk of certain birth control-related side effects, like venous thromboembolism (VTE).

VTE occurs when blood clots form in your veins. The use of combined hormonal contraceptives, which are birth control methods that contain both estrogen and progestin, increases the risk of VTE, and so does obesity.

This means women with obesity who use combined hormonal contraceptives have a higher risk of developing blood clots, which can lead to serious health conditions like a heart attack or stroke.

These methods include combination birth control pills, the vaginal ring, and the birth control patch. If you have obesity and are interested in using one of these methods, it may still be a good fit for you depending on your health history. It is worth discussing the risks versus benefits with your doctor.

That said, experts suggest the safest and most effective forms of birth control for women with obesity are:

  • progestin-only birth control pill
  • birth control shot
  • long-acting reversible contraception, such as IUDs and contraceptive implants

Read on to learn more about birth control options for people with obesity.

Progestin-only pill

The progestin-only birth control pill, or minipill, only contains the hormone progestin, which is a type of hormone naturally found in women’s bodies.

The pill needs to be taken at the same time every day to be the most effective. This method does not protect against sexually transmitted infections (STIs).

  • How it prevents pregnancy: Progestin-only birth control helps prevent pregnancy by stopping ovulation and thickening cervical mucus, which prevents sperm from reaching your eggs.
  • Is it safe for larger bodies? Progestin-only birth control is considered safer for people in larger bodies because it is not associated with an increased risk of VTE.
  • Possible side effects: Progestin-only birth control may cause minor side effects, like breast tenderness, nausea, and spotting or irregular bleeding.

Birth control shot

When progestin is given as an injection, it’s known as a birth control shot, or Depo-Provera. You get this injection at your doctor’s office every 13 weeks. This method does not protect against STIs.

  • How it prevents pregnancy: Progestin-only birth control helps prevent pregnancy by stopping ovulation and thickening cervical mucus, which prevents sperm from reaching your eggs.
  • Is it safe for larger bodies? Progestin-only birth control is considered safer for people in larger bodies because it is not associated with an increased risk of VTE.
  • Possible side effects: Progestin-only birth control may cause minor side effects, like breast tenderness, nausea, and spotting or irregular bleeding.

Studies show that progestin-only birth control is not significantly associated with weight gain. But some evidence suggests the injectable progestin-only contraceptive depot medroxyprogesterone acetate (DMPA), also known as Depo-Provera, may lead to weight gain.

However, a 2020 study that included 240 women found that those with obesity were not more susceptible to Depo-Provera-related weight gain than women without obesity.

IUD

An intrauterine device (IUD) is a tiny device that’s inserted into your uterus.

There are two types of IUDs: hormonal and copper. Copper IUDs do not contain hormones. Hormonal IUDs only contain progestin, so they’re safe for women in larger bodies. IUDs do not protect against STIs.

  • How it prevents pregnancy: Hormonal IUDs work by thickening cervical mucus, inhibiting sperm movement, and thinning the lining of your uterus, which prevents pregnancy. The copper IUD works by preventing sperm from reaching your eggs.
  • Is it safe for larger bodies? Yes, both types of IUDs are safe and effective for all body sizes.
  • Possible side effects: Hormonal IUDs can help improve heavy periods, cramps, and premenstrual syndrome (PMS). However, they are associated with some side effects, like pain during and after insertion, spotting, and irregular periods. The copper IUD can also cause pain during and after insertion and irregular periods, heavier periods, and a worsening of cramps.

Even though the IUD insertion process can be painful, most IUD-related side effects subside in a few months. Plus, IUDs are one of the most convenient forms of birth control: They last 3 to 12 years, depending on the type you choose.

Contraceptive implant

A contraceptive implant or birth control implant is a tiny, matchstick-sized rod that’s inserted under the skin of your upper arm.

Birth control implants use progestin to prevent pregnancy, so they’re safe for all body sizes.

  • How it prevents pregnancy: Birth control implants release a small amount of progestin, which helps prevent pregnancy by thickening cervical mucus and stopping ovulation.
  • Is it safe for larger bodies? Progestin-only birth control is considered safe for women in larger bodies because it is not associated with an increased risk of VTE.
  • Possible side effects: Progestin-only birth control may cause minor side effects, like breast tenderness, nausea, and spotting or irregular bleeding.

Birth control implants are convenient because they can last for up to 5 years. Plus, the insertion process is easy and isn’t usually painful. This method does not protect against STIs.

Barrier methods

These methods include condoms and internal condoms, which help protect against STIs. Other barrier methods that do not protect against STIs are diaphragms and cervical caps, which are used with spermicide, and the birth control sponge.

  • How they prevent pregnancy: Barrier methods prevent pregnancy by physically preventing sperm from entering the uterus.
  • Are they safe for larger bodies? With correct and consistent use, barrier methods are safe and effective for all body sizes.
  • Possible side effects: Since these methods do not contain hormones, there are few side effects. The use of spermicide with certain methods may irritate sensitive skin.

While combined hormonal contraceptives are effective in preventing pregnancy in women with obesity, they are not always recommended because they may raise the risk of developing VTE.

However, there are two methods that may actually be less effective in preventing pregnancy for women in larger bodies.

Birth control patch

Research has shown that one long-term birth control method, transdermal birth control patches, may be less effective at preventing pregnancy in women in larger bodies. This method is not recommended for people who weigh more than 198 pounds (89.8 kilograms).

Morning-after pill

Emergency contraceptive pills, commonly known as morning-after pills, are also less effective for women above a certain weight.

Levonorgestrel, also known as Plan B, does not work as well for women who weigh more than 165 pounds (74.8 kg). Ella is another type of morning-after pill that loses its effectiveness in women who weigh more than 195 pounds (88.4 kg).

Studies suggest that women with obesity are four times as likely to get pregnant after using emergency contraception containing levonorgestrel than women who do not have obesity.

But in an emergency, you do have another option. Regardless of your weight, getting an IUD inserted within 5 days after having sex without a birth control method is considered the most effective type of emergency contraception.

Most forms of birth control, including progestin-only pills and shots, IUDs, and birth control implants, are highly effective at preventing pregnancy in all women, regardless of body size.

However, both obesity and the use of combined hormonal contraceptives that contain estrogen may increase the risk of blood clots and other health issues, so women with obesity who are considering these methods should discuss the risks and benefits with their doctor.

What’s more, birth control patches and the morning-after pill may not be as effective for women who are over a certain body weight.

Even without combined hormonal contraceptives, there are plenty of safe and effective birth control options for people in larger bodies.

If you have any questions or need advice on birth control, make an appointment with your doctor to find the method that’s right for you.