Researchers studied whether hormonal birth control increases the risk of stress fractures (tiny cracks in bones from overuse) in active-duty female military members. They compared 1,689 women who had stress fractures with similar women who didn’t. The study found that most types of birth control don’t increase fracture risk. However, birth control pills, patches, and vaginal rings used for 2-3 years showed a possible link to more fractures. The researchers say more study is needed before drawing firm conclusions, and overall, hormonal birth control appears safe for active military women.

The Quick Take

  • What they studied: Whether different types of hormonal birth control increase the chance of getting stress fractures (small cracks in bones from intense exercise) in female soldiers
  • Who participated: 1,689 female active-duty military members who had stress fractures, compared with similar women who didn’t have fractures. Participants were matched by age, race, military branch, and time in service
  • Key finding: Most birth control methods showed no increased fracture risk. Only birth control pills, patches, and vaginal rings used for 2-3 years showed a possible increased risk (about 2 times higher), but this finding needs more research to confirm
  • What it means for you: If you’re a female soldier or very active woman, most hormonal birth control methods appear safe for bone health. If you use pills, patches, or rings long-term, discuss bone health with your doctor, especially if you have other risk factors. This single study shouldn’t change your birth control choice without talking to your healthcare provider

The Research Details

This was a case-control study, which is like comparing two groups of people: those who experienced something (stress fractures) and those who didn’t. Researchers looked backward in time to see what birth control methods each group used in the two years before the fracture occurred.

The study carefully matched women in the fracture group with women in the non-fracture group based on important factors like age, race, military branch, and how long they’d been serving. This matching helps ensure any differences found are more likely due to birth control use rather than other factors.

Researchers separated birth control types into groups based on how they work in the body: IUDs, implants, and injectables were studied separately, while pills, patches, and vaginal rings were studied together because they work similarly.

This research approach is important because stress fractures are a real problem for female soldiers—they happen more often in women than men and can affect military readiness. By comparing women who got fractures with similar women who didn’t, researchers can identify whether birth control might play a role. The careful matching of groups helps reduce confusion from other factors that might cause fractures, like fitness level or nutrition

Strengths: The study was approved by an ethics board, used a large sample size (1,689 cases), and carefully matched comparison groups. Researchers adjusted their analysis for important factors like obesity and military rank that could affect fracture risk. Limitations: The study only looked backward in time, so it can’t prove birth control caused fractures. The finding about pills/patches/rings was based on a smaller number of women and needs confirmation. The study couldn’t measure all factors affecting bone health, like vitamin D levels or exercise intensity

What the Results Show

The main finding was reassuring: most types of hormonal birth control showed no increased risk of stress fractures in female soldiers. IUDs, implants, and injectables were not associated with higher fracture risk at all.

However, one finding stood out: women who used birth control pills, patches, or vaginal rings for 2-3 years had about twice the risk of stress fractures compared to women not using these methods. This association only appeared after researchers adjusted for obesity and military rank—before that adjustment, no birth control method showed increased risk.

Women with stress fractures were more likely to be vitamin D deficient, overweight, or have a history of bone problems. These factors likely played a bigger role in fracture risk than birth control use.

The study found that enlisted women (lower-ranking soldiers) had more stress fractures than officers. Women with vitamin D deficiency were overrepresented in the fracture group, suggesting this nutrient is important for bone health in active women. Obesity was also more common in women with fractures, indicating that weight management may be important for bone strength during military service

Previous research has suggested that hormonal birth control might affect bone density (bone thickness), but this study found little evidence that this translates to more fractures in young, active women. The possible link between pills/patches/rings and fractures after 2-3 years is new and contradicts some earlier research suggesting these methods are safe. This disagreement is why the researchers call for more investigation

The study looked backward in time, so it can’t prove birth control caused fractures—only that an association exists. The finding about pills/patches/rings was based on a relatively small number of women (making it less reliable). The study couldn’t measure all important factors like calcium intake, vitamin D levels, or how intensely women exercised. Women who stayed in the military longer might have different health profiles than those who left, which could skew results. The study only included active-duty members, so results may not apply to civilian women

The Bottom Line

For most female soldiers: Continue using your current hormonal birth control if it’s working for you—the evidence suggests it’s safe for bone health. For women using pills, patches, or vaginal rings long-term: Discuss bone health with your military doctor, especially if you have risk factors like vitamin D deficiency, low body weight, or family history of osteoporosis. All active women: Ensure adequate vitamin D and calcium intake, maintain healthy weight, and include strength training in your fitness routine. These factors likely matter more than birth control choice for bone health. Confidence level: Moderate—this is one study that needs confirmation

This research is most relevant to female active-duty military members, especially those considering birth control or currently using pills, patches, or rings. It’s also useful for healthcare providers advising active women about contraception. Civilian women may find this helpful, but military women face unique physical demands that might not apply to the general population. Men don’t need to worry about this research

If there is a real effect of birth control on fracture risk, it appears to develop over 2-3 years of use, not immediately. Benefits of switching birth control methods (if recommended by your doctor) would likely take months to appear. Bone health improvements from better nutrition and exercise typically show up over 6-12 months

Want to Apply This Research?

  • Track birth control use type and duration alongside any bone-related symptoms (shin pain, stress fractures, or bone injuries). Log this monthly to identify patterns over time
  • Set reminders to track vitamin D and calcium intake daily (aim for 1,000-1,200 mg calcium and 600-800 IU vitamin D). Add strength training 2-3 times weekly, focusing on weight-bearing exercises like running, jumping, or resistance training
  • Every 3 months, review your birth control type, nutrition intake, exercise routine, and any bone-related issues. If using pills/patches/rings long-term, discuss bone health screening with your healthcare provider annually

This research summary is for educational purposes only and should not replace professional medical advice. The findings are from a single study and need confirmation through additional research. If you’re considering starting, stopping, or changing birth control, or if you have concerns about bone health, consult with your healthcare provider or military medical officer. They can evaluate your individual risk factors and help you make the best decision for your health. This study does not establish that birth control causes fractures, only that a possible association exists that requires further investigation.