Choosing the right birth control for the first time or thinking about changing your current method can be overwhelming.

There are numerous options available, such as implants, IUDs, and more. A discussion with your doctor about which contraceptive may suit your sexual and reproductive health best can be very beneficial.

Experts share insights on the most widely prescribed contraceptive method in the U.S.: the birth control pill.

What is the Birth Control Pill?

Dr. Jennifer Robinson, MD, MPHTM, PhD, an obstetrician/gynecologist and assistant professor in Gynecology and Obstetrics at Johns Hopkins School of Medicine, states, “The birth control pill is the most prevalent and recognizable form of prescription contraceptive.”

According to Dr. Gina Frugoni, MD, an assistant professor of Obstetrics, Gynecology, and Reproductive Sciences at UC San Diego School of Medicine and obstetrician/gynecologist at UC San Diego Health, “The pill is a daily hormonal medication utilized by those with ovaries and a uterus to avoid pregnancy.”

There are two types of birth control pills: the combined oral contraceptive pill and the progestin-only pill (also known as the minipill). The key distinction between them lies in their hormone content. The combined pill includes both estrogen and progestin, while the progestin-only pill contains solely progestin, reports Healthline.

The combined pill is the most frequently prescribed oral contraceptive, notes Robinson. The progestin-only pill, though less common, may be recommended for those who are breastfeeding, have concerns about estrogen, or are at risk for complications such as blood clots, high blood pressure, or heart issues, as per Mayo Clinic.

How Do Birth Control Pills Work?

Robinson explains that, “Most birth control methods work through several mechanisms to prevent pregnancy.”

The combined pill primarily prevents ovulation. Taking the pill sends signals to the brain indicating that there’s no need for ovarian stimulation, which halts the release of an egg, according to Frugoni. Without an egg, pregnancy can’t happen.

In addition, the combined pill causes the cervical mucus to thicken, forming a barrier that impairs sperm function, explains Robinson.

The progestin-only pill also thickens cervical mucus, as noted by the Mayo Clinic. However, it has some differences. While progestin can sporadically prevent ovulation, it may not do so consistently. Research shows that about 40% of women may still ovulate while on the progestin-only pill, according to The American College of Obstetricians and Gynecologists. Additionally, the progestin-only pill can thin the endometrium, making it harder for an egg to implant into the uterus, per Healthline.

What Are the Side Effects of Birth Control Pills?

Common side effects of the combined pill may include breast tenderness, nausea, headaches, and spotting, as reported by ACOG. Although rare, serious side effects such as blood clots, strokes, or heart attacks can occur. There is also a possibility of developing high blood pressure from taking the pill, according to the FDA.

The progestin-only pill may lead to side effects such as acne, breast tenderness, nausea, headaches, irregular bleeding, and weight gain, per FDA guidelines.