Birth Control & Fertility

Updated: 22 Nov 2025

This page explains how different birth control methods change pregnancy chance and how perfect use compares to typical use in real life.

If you want to explore example numbers, you can use tools such as the Condom Risk Calculator, the Pill Risk Calculator, the Combine Methods Calculator or the Advanced Pregnancy Chance Calculator. The sections below give a plain language overview and point to these tools where they are most relevant.

Method snapshots

Barrier methods (condoms, diaphragms)

  • Work best when used consistently and correctly. Slips, breaks and late withdrawal are the main reasons for higher pregnancy rates.
  • If you want to see how this plays out with intercourse count and use quality, you can try the Condom Risk Calculator.

Hormonal methods (pill, patch, ring, shot)

  • Missed or delayed doses are the main source of extra risk. Reminders, routine and clear instructions help keep protection close to the labelled rates.
  • The Pill Risk Calculator shows typical versus perfect use and how the chance builds across a cycle.

Long-acting reversible contraception (IUDs, implant)

  • Offer very low pregnancy rates in day-to-day use when insertion and replacement are on schedule.
  • For people using an implant who are close to or past the labelled duration, this explainer looks at the research: Implant effectiveness over time.

Fertility awareness and withdrawal

  • Highly dependent on user skill and consistency. Accurate cycle tracking helps, but there is little buffer for mistakes or unexpected early ovulation.
  • Many people using these methods also keep condoms on hand as a backup on higher risk days.

Combining methods

Using two methods together can lower the chance of pregnancy further, but some pairings add more protection than others. For example, condoms plus a hormonal method usually reduce risk more than doubling up on two barrier methods.

You can see how different pairings compare in the Combine Methods Calculator, and the article on best and worst contraceptive method combinations walks through common examples.

Tip: When you use any calculator, it is often helpful to look at both perfect and typical use to get a realistic range.

FAQ

Does hormonal birth control harm long-term fertility?
No clear evidence of permanent harm has been found in large studies. Cycles may take time to normalise after stopping, and timing varies by method and by person.
What actually causes most “failures”?
Most unintended pregnancies on birth control are linked to missed or late doses, late or incorrect condom use, device timing (insertion or replacement) and intercourse on higher risk days without a backup method.
Should I use perfect or typical use in your tools?
If you sometimes slip on timing or technique, choose typical. If you are consistently precise with doses and instructions, choose perfect. You can compare both to see a likely range.
What if I use two methods?
The Combine Methods Calculator estimates the combined effect of two methods. Some pairs add a large extra margin of safety. Others overlap and add little, especially if both are already highly effective on their own.

Educational content only; not medical advice. For personalised guidance, consult a qualified clinician. Choice of birth control method is best made with a doctor, nurse or clinic that knows your medical history.

Check Out Our Latest Contraceptives and Fertility Posts

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