I want my teenage daughter protected against pregnancy, but is birth control bad for her bones?

A: Most types of birth control are safe for teenage bones.

Birth control has many benefits for teens. Preventing an unwanted pregnancy is really important. Birth control can also help decrease menstrual cramps and bleeding, improve acne, and treat endometriosis and polycystic ovarian syndrome. Most types of birth control appear safe for teenage bones. If a teen is underweight, has an eating disorder, or exercises at a high level, it’s important for them to talk with their clinician about their bone health.

In female-bodied people, estrogen is crucial for healthy bones. During early puberty, estrogen levels increase, signaling the bones to lengthen. This causes the “growth spurt” that results in 5th grade girls towering over the boys! This growth spurt is nearly complete by the time of the first menstrual period, around age 12. During the early teen years that follow, estrogen then causes the bones to become denser and therefore stronger. Bones reach their peak density around age 20. After that, bone density stays steady or decreases slightly until menopause. Then, estrogen levels fall significantly , and so does bone density, increasing the risk for osteoporosis (thin, weak bones) and fractures. Estrogen replacement therapy after menopause has been shown to improve bone strength and help prevent fractures.

In adults, studies show that birth control pill users have slightly higher bone density and lower fracture risk than non-users, likely due to slightly higher estrogen levels. The implant and intrauterine devices have shown no association with bone health, likely because they have less of an impact on the body’s hormone levels. The shot (DepoProvera), which lowers total body estrogen, is associated with a slight decrease in bone density, in the same range as what occurs during a typical pregnancy. This loss is temporary and reverses when the person stops using the method.

In teens, use of birth control pills does not interfere with the growth spurt or final height. In part, this is because clinicians do not prescribe birth control to people who are not yet menstruating. Studies of birth control’s effect on bone density are difficult to do in teens because so much is changing with bones at that age. Results on bone density have varied, but studies have not found any impact of birth control use on fracture risk in teens.

The two most powerful influences on bone health in teens are nutrition status and exercise. For example, being underweight is associated with a 3x higher risk of fracture, and eating disorders are associated with an 8x higher risk! Exercise generally improves bone density, but too much can be harmful. In activities such as long-distance running, gymnastics, and dance, training more than 12-16 hours per week is associated with almost double the fracture risk. Getting enough calcium and vitamin D reduces risk of fracture by about half.

Bottom Line: Bone health is important, especially during the teen years when bones are building strength. Most types of birth control do not seem to cause any harm to teenage bones and have many potential health benefits. The most important step to take for bone health in teens is ensuring good nutrition and reasonable physical activity. Teens should talk with their clinician about their individual situation and what type of birth control is best for them.