Science of Sex: BMI And Birth Control Efficacy

March 30th, 2019

bmi and birth control efficacy

This month’s very late Science of Sex post was motivated by the new Hulu show Shrill, which reminded the world that emergency contraception may not be as effective for overweight people. Specifically, the brand Plan B (also known as the morning after pill) EC is rated up to 175 pounds, which is just over the average weight of an American woman.

The results of a large European study show that the popular form of EC, levonorgestrel 1.5 mg, (Plan B pill) loses its potency in women weighing about 165 pounds and does not work at all in women weighing 175 pounds or more.

There are several theories as to why.

  1. Having more fat makes pills break down more quickly. This makes the medication less effective.
  2. Overweight people have more blood, so more birth control is required to reach ideal blood concentration levels.

Researchers haven’t pinpointed which theory, if either, is correct. All we know is that EC might not be reliable for many people. This was something I learned last year thanks to Reddit, but it’s not something that many people have heard from doctors, pharmacists, or other professionals. Even the manufacturer denies this to be the case.

Fortunately, there is another option: Ella. According to the study, Ella is more effective than Plan B for overweight users, and you can take the pill up to five days later. In comparison, Plan B loses effectiveness after 72 hours. However, you may need a prescription for Ella.

Ella bested Plan B by half, with about 50% fewer pregnancies than those taking levonorgestrel.

Additionally, you may be able to double up on doses of Plan B to increase its effectiveness if you are overweight.

This increased risk of pregnancy doesn’t end with EC. Cochrane examined different studies and found mixed results. The effectiveness of birth control didn’t decrease universally as BMI increased, but the patch and some birth control pills were less effective for overweight and obese users. Shots, implants, and hormonal IUDs were not less effective.

Across the board, IUDs are touted as being the most effective birth control or EC regardless of BMI.

But any contraception is better than none. The European Medicines Association advises that using Plan B is better for overweight people than using no EC. You just need to be aware of the risks.

Further Reading

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Categories: Science of Sex

Science of Sex: Birth Control

May 13th, 2017

Welcome to the third installment in a new feature on Of Sex and Love: Science of Sex. In this feature, I plan to discuss the science of sexuality in an easy-to-digest format that’s accessible to the casual reader. I will also follow up with some extended reading material for people who want to know more about the subject of each post.

Enjoy!

science of sex birth control

Barrier methods of birth control, including condoms, cervical caps, diaphragms and the sponge block sperm from moving through the cervix to the uterus, where it would otherwise fertilize an egg. If the barrier becomes compromised, say, by a pinhole or friction, it’s less effective.

Barrier methods are sometimes combined with spermicide in the form of nonoxynol-9. As I mentioned in my previous Science of Sex post on lube, nonoxynol-9 is detrimental to sperm, but it can also have a caustic effect on your sensitive vaginal tissues and can even make it more likely to contract an STI.

Hormonal birth control varies, however. The regular birth control pill, which contains a combination of both estrogen and progestin, a synthetic form of progesterone.

During a woman’s menstrual cycle, estrogen peaks, signaling for her pituitary gland to release other hormones (follicle stimulating hormone and luteinizing hormone, to be specific). This leads to the release of an adult egg, which can be fertilized if sperm makes its way to the egg.

When a woman is on combination birth control, the hormones create a balance and that estrogen spike is prevented from occurring, so no egg is released. Progestin also makes a woman’s uterine lining less ideal for hosting a fertilized egg. Other hormonal birth control methods, including the patch and NuvaRing, work in a similar way.

However, not every form of hormonal birth control contains a combination of hormones. The progestin-only pill (called a POP or mini-pill) lacks estrogen as the name suggests. These pills are less effective than combination birth control. Because they have no estrogen, these forms of birth control may allow more breakthrough bleeding than combination birth control.

Progestin-only birth control may be prescribed to women who are breastfeeding (breastfeeding naturally prevents ovulation, but the mini-pill in addition to breastfeeding is more effective than breastfeeding alone) as well as those who suffer from migraines. Combination pills were once believed to contribute to migraine headaches; however, more recent science suggests that this may not be the case and that combination BC may even help prevent migraines. Nevertheless, taking combination birth control if you already experience migraines with auras might contribute toward strokes.

The Mirena and Skyla IUDs (in the form of levonorgestrel), Implanon, and Depo-Provera are progestin-only BC methods.

Most birth control falls into the category of barrier or hormonal methods, but copper IUDs alone take a different route. Copper IUDs (Paragard in the US) are sometimes known as just a copper-T or coil and work by releasing small amounts of copper into your blood stream. Copper is an effective spermicide without the side effects of nonoxynol-9, damaging sperm so to prevent fertilization. Copper IUDs may also prevent ovulation.

Further Reading

Did you enjoy the second installment of Science of Sex? Do you have further questions or suggestions for next month’s subject? Leave me a comment!

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Categories: Science of Sex

lingerie

I Haven’t Used a Condom in 8 Years

May 16th, 2014

Condoms in a rowThis was a post that I thought of not too long ago. It struck me that most single people use condoms as both birth control and to protect against sexually transmitted infections, but my case is a little different.

It’s been over eight years since I last used a condom. In fact, the only person I’ve ever used a condom with was my ex-husband. However, shortly after moving to Japan to live with him on a military base, I got my first IUD. I kept that in longer than the FDA-recommended 5 years in the US. Mirena is rated for 7 years overseas, and I wasn’t sexually active for several years after my divorce.

My first sexual experience occurred in early 2013, and by that time, I was using my second IUD. I hadn’t had it in very long — maybe 6 weeks — and I can honestly say that I should have used a condom with this new partner, but I didn’t. I did, however, wind up taking Plan B and making an extra appointment at Family Planning. Everything was fine.

Since then, I’ve had only one partner, the bartender, and we’ve never used condoms. I don’t mind condoms as a whole, but I never wanted to use them with him. I wanted — and continue to want — to feel him. He asked about condoms the first time we had sex, but I set a precedent that we follow more than a year later.

In all, I haven’t used condoms in almost a decade. I’ve handled them only to stuff a Halloween pumpkin pinata full of alcohol, condoms and booze. There are a hanful floating around my bedroom thanks to sex toy retailers that send condoms and lube samples with their packages. If I need a condom, I know where to go.

However, they’re just not part of my sex life in a natural way. I don’t carry condoms in my purse. Nor do I have them in my pocket or make sure to grab them when I think that I might have sex. Indeed, I no longer think about condoms with lubes or bumps or ridges. I don’t care about condoms that heat up or cool down or are made of mesh. To be honest, I wouldn’t necessarily mind that. I didn’t dislike condoms as much as I do silicone lube, which seems to create a far greater barrier between me and my partners.

The bartender loves — and I cannot emphasize this enough — loves cumming in me.  I haven’t been able to get him to cum in my mouth because he loves orgasm during penetration so much. It’s almost amusing that he doesn’t want to deviate from that. It’s endearing; although, condoms certainly do make for a less messy sexual experience. But that alone isn’t enough to justify the cost of condoms when I have another, better method of birth control.

For many people, condoms are the answer, but I am not one of those people, at least, not at this point in my life.

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Image © MisterUnlucky; used with permission.