This Week in Sex is a summary of news and research related to sexual behavior, sexuality education, contraception, STIs, and more.

Genetic Variation Could Screw With Your Birth Control 

Let’s face it: When a doctor learns a patient on the birth control pill is pregnant, they probably assume that that it’s the patient’s own damn fault. After all, when used perfectly, the birth control pill is considered 99 percent effective. But like many methods that require users to do something and do it right, the real-life efficacy rate is lower (91 percent in the case of the pill). So, when a user gets pregnant, health-care providers are likely to jump to the conclusion that the patient forgot a pill or two or three.

A new study suggests an intriguing reason that hormonal methods might fail: genetic variations that mean the body processes the active ingredients in hormonal birth control differently.  The study was conducted among users of the contraceptive implant—a small rod that is inserted underneath the skin of a person’s arm—but the researchers believe the results could affect daily pill users.

University of Colorado researchers recruited 350 women who had been using the contraceptive implant for one to three years. They chose this method because it uses the same hormones as the birth control pill and stops ovulation, but also because once an implant is inserted, it automatically releases hormones over time. There is no need to account for user mistakes such as a missed pill.

Researchers specifically looked at three genetic variants that have been linked to hormone levels in the blood. Hormonal birth control methods suppress ovulation by keeping hormone levels steadily elevated during a person’s menstrual cycle. If these genetic variants affect how the body metabolizes hormones, they could cause reduced efficacy of birth control pills or other hormonal methods.

The finding were strongest for one gene known as CYP3A7*1C. During fetal development, the gene produces a protein that can break down hormones like those in birth control. In most infants, the gene is switched off after birth, but some women continue to produce the protein throughout their lives.

This study found that about 5 percent of participants had this genetic variation and were still making this protein. Among those with this variation, 28 percent had estrogen levels that fell below the hormonal threshold that the implant is supposed to maintain.

But don’t panic, throw out your pill packs, or get your implant removed just yet. This is a very small study, and only 18 participants had this genetic variation and only five of them had lower levels of estrogen in their blood. And body mass index and longer use of the implant could also account for lowered estrogen levels.

Most importantly, the researchers who conducted this study don’t believe that the blood-hormone levels were low enough to put these participants at risk of pregnancy because the threshold the implant is supposed to maintain is higher than necessary. Dr. Aaron Lazorwitz, the study’s lead author, explained to CNN that he doesn’t think implant users are at increased risk of conceiving while using contraception. But he said this research, if proven correct, could have implications for birth control pill users because the pills aim for a lower concentration of hormones to begin with.

The authors acknowledge that much more research has to be done before they can reach any real conclusions. For now, Lazorwitz’s main point is pretty simple. He told Wired: “The biggest takeaway is that we’ve assumed for so long that if a woman taking birth control gets pregnant, then she must have done something wrong …. Instead, maybe we need to pay more attention as physicians to other things that might be going on, like genetics, so we can give better, more individualized treatment to women instead of just blindly adhering to the motto that if you just throw some hormones at it, that usually fixes the problem.”

Another Pill Recall

While we’re on the subject of birth control, we want to draw your attention to a recall of pills due to packaging errors.

The FDA announced a recall by generic drug company Apotex Corp., of four lots of drospirenone and ethinyl estradiol USP. The affected lots expire in August 2020 and are printed with the lot numbers 7DY008A, 7DY009A, 7DY010A and 7DY011A.

The packages may have mixed active pills with the placebo pills that users take during their period, have pockets with no pill in them, or have both problems. Taking a placebo at the wrong time or missing an active pill during the month could make a user vulnerable to pregnancy. A similar recall of out-of-order pills by maker Allergan happened last May.

If you have one of these packets, return it to your pharmacy and get a replacement. Anyone who is worried that they might be pregnant due to this error should see their health-care provider.

An Oral Sex Risk You’ve Probably Never Imagined

A story in the March issue of BMJ Case Reports has all the elements of a medical mystery, and it’s worthy of House with a dash of Grey’s Anatomy-style sex. A 31-year-old woman was treated in a Spanish emergency room for a severe allergic reaction marked by difficulty breathing, vomiting, and hives.

But it came not after eating a new food—but after engaging in oral sex with her male partner.

A latex allergy could have explained this response after oral sex, except that the couple had not used a condom or a dental dam during their encounter. There is also a known condition called seminal plasma allergy (SPA) or human seminal plasma hypersensitivity (HSP). A study published in the Mount Sinai Journal of Medicine suggests that as many as 40,000 U.S. women might have this condition, which makes conceiving difficult because they cannot have unprotected sex without a reaction to sperm. The doctors in Spain, however, did not believe this is what happened to their patient because she had engaged in sex before with no problems.

The aha! moment came when the patient explained that she had gotten hives as a child when she was prescribed the antibiotic amoxicillin. It turns out that her partner was on the fifth day of a course of the drug Augmentin—which is a combination of amoxicillin and clavulanic acid—to treat an ear infection. He had taken his medication just a few hours before they had sex (we can only assume he was feeling better).

Certain antibiotics can travel in high doses to the prostate gland, one of the glands that contributes to semen production. So doctors now suspect that this patient inadvertently got a dose of her partner’s antibiotics.

This one case certainly does not mean that anyone allergic to penicillin should stop going down. We here at This Week in Sex just see this as more proof that communication between sexual partners is a really good idea. If you’re one of the 1 percent of the U.S. population who is allergic to penicillin (or the 10 percent who thinks they are), tell your partner and ask for a heads up whenever they start taking an antibiotic. It might save you a trip to the emergency room and some rather painful symptoms.

Reminder: Condoms and Staplers Don’t Mix

A young Texas barbershop owner had a great idea to promote his business: giving away condoms with his business card attached because, as he said in a tweet, “You’re going to need them after I cut your hair. Trust me.”

We might trust him with our hair. But based on the photo he tweeted out, we will never trust him with our birth control. You see, the barber’s plan had a fatal (or make that “fertile”) flaw. He attached his business card to the condom package with a stapler.

Those two pin-prick holes right through the middle of the condom can let sperm, bacteria, or viruses through. In other words, they basically defeat the condom’s entire raison d’etre.

Great idea, failed execution. If anyone else wants to promote their business and condom use simultaneously, might we suggest having some nice stickers to shout out your services?