Birth control products contain a wide range of materials depending on the type, from synthetic hormones and plastic polymers to copper wire and natural rubber. Most hormonal methods rely on lab-made versions of progesterone, sometimes paired with a synthetic estrogen. Non-hormonal options use physical materials like copper, latex, or chemical agents that disable sperm. Here’s what goes into each major type.
Combination Pills: Synthetic Estrogen and Progestin
Combination birth control pills contain two active ingredients: a synthetic estrogen and a synthetic progestin. The estrogen component in most pills is ethinyl estradiol, a lab-made version of the estrogen your body naturally produces. It works by binding to the same receptors as natural estrogen, suppressing ovulation and stabilizing the uterine lining. Most combination pills contain between 10 and 35 micrograms of ethinyl estradiol per tablet.
The progestin component varies more. Three synthetic progestins are commonly used in the United States: norethindrone, norgestrel, and drospirenone. Each mimics the effects of natural progesterone, thickening cervical mucus so sperm can’t easily reach an egg and thinning the uterine lining. Different progestins have slightly different chemical profiles, which is why switching pill brands can change side effects like bloating, mood, or skin breakouts.
What might surprise you is how little of each pill is actually hormones. Research from MIT found that for most medications, more than half of the pill’s weight comes from inactive ingredients, and for some drugs that figure reaches 99 percent. Birth control pills are packed with fillers and binders like lactose, corn starch, and magnesium stearate. These give the pill its shape, help it dissolve properly, and make it large enough to handle. About 93 percent of medications contain at least one potential allergen in their inactive ingredients, including lactose and chemical dyes, which is worth knowing if you have food sensitivities or unexplained reactions to a particular brand.
Progestin-Only Methods
Several birth control options skip estrogen entirely and deliver only a progestin. These include the mini-pill, the hormonal IUD, the implant, and the injection. Each uses a different synthetic progestin and a different delivery system, which means the physical materials vary quite a bit.
The Implant
The contraceptive implant (sold as Nexplanon) is a small, flexible rod about the size of a matchstick, inserted under the skin of the upper arm. Its core is made of ethylene vinyl acetate (EVA), a soft plastic copolymer. Embedded in that core are 68 milligrams of etonogestrel, a synthetic progestin that slowly releases over three to five years. The rod is wrapped in a thin EVA skin that controls how quickly the hormone seeps out. Nexplanon also contains barium sulfate, which makes the implant visible on an X-ray so a doctor can confirm its position.
The Injection
The contraceptive shot (Depo-Provera) delivers a progestin called medroxyprogesterone acetate, a chemical derivative of natural progesterone. It’s suspended in a water-based solution that includes polyethylene glycol (a common stabilizer found in everything from skin cream to toothpaste) and sodium sulfate. A preservative keeps the solution sterile. Once injected into muscle tissue, the hormone releases gradually over about three months.
Progestin-Only Pills
The mini-pill contains the same types of inactive fillers as combination pills but carries only a progestin. The three formulations currently available in the U.S. use norethindrone, norgestrel, or drospirenone as their active ingredient.
The Copper IUD
The copper IUD is the only widely used hormone-free device that provides long-term contraception. Its frame is made of plastic, specifically a composite of low-density polyethylene mixed with barium sulfate (the same radiopaque agent used in the implant, included so the IUD shows up on imaging). Copper wire is wound around the plastic frame. The copper itself is the active ingredient: it creates an environment inside the uterus that is toxic to sperm, impairing their movement and viability. No hormones are involved at any point.
The copper also triggers a mild inflammatory response in the uterine lining, which further reduces the chance of a fertilized egg implanting. This is why copper IUDs can cause heavier periods, especially in the first few months. The device contains enough copper to remain effective for up to 10 years.
Condoms and Barrier Methods
Most condoms are made from natural rubber latex, a milky fluid harvested from rubber trees. Latex condoms are the most widely available and tend to be the least expensive. For people with latex allergies, two main alternatives exist. Polyurethane condoms are made from a thin plastic film. They transfer heat better than latex, but they’re slightly less stretchy and more prone to slipping. Polyisoprene condoms are made from synthetic rubber that mimics the feel and elasticity of latex without containing the proteins that trigger allergic reactions.
Lambskin condoms, sometimes called natural membrane condoms, are made from the intestinal lining of sheep. They block sperm but have microscopic pores large enough to allow viruses through, so they don’t protect against sexually transmitted infections.
Other barrier methods like diaphragms and cervical caps are typically made from medical-grade silicone, a flexible, hypoallergenic material that can be washed and reused.
Spermicides
Spermicides are chemical contraceptives designed to kill or disable sperm on contact. Nearly all spermicide products sold in the U.S. use the same active ingredient: nonoxynol-9, a surfactant that disrupts sperm cell membranes. The concentration varies significantly depending on the delivery format. Spermicidal film contains 28 percent nonoxynol-9, foams typically contain around 12.5 percent, and gels range from 2 to 4 percent. Lower concentrations generally mean the product needs more contact time to work.
The remaining ingredients are the delivery vehicle: gels use water-based thickeners, foams include propellants, and films dissolve from a thin sheet into a gel-like barrier over the cervix. Spermicides are available over the counter without a prescription and have no age restrictions, though they’re considerably less effective than hormonal methods when used alone.
Surgical Sterilization Devices
Tubal ligation, the most common form of permanent contraception, sometimes involves small clips or bands placed on the fallopian tubes. The Filshie clip, one of the most widely used devices, is made of titanium lined with silicone rubber. The titanium provides the structural strength to keep the tube closed, while the silicone lining applies continuous pressure even after normal metal fatigue affects the titanium over time. Silicone bands, used in a different technique, are made entirely of medical-grade silicone and work by cinching a small loop of the fallopian tube shut.
In cauterization methods, no foreign material is left behind at all. The tubes are sealed using electrical current or heat, which destroys a small section of tissue and creates scar tissue that blocks the passage permanently.