Plan cycle dates after contraceptive implant removal using your dates and cycle history. See an ovulation forecast, first-period window and a test date for the forecast.
* These dates and percentages are a planning forecast. Fertility can return quickly after implant removal; pregnancies have occurred within 7–14 days. Use contraception if you do not want to become pregnant. Test from the first day of a missed period, or at least 21 days after the last unprotected sex if your next period date is uncertain. You do not need to wait for the forecast test date.
Methodology & Sources
What this estimates
The forecast percentages describe the timing curve shown, rather than contraceptive protection after removal. Pregnancy testing does not need to wait for the forecast date. See NHS pregnancy-test timing guidance and Nexplanon prescribing information, section 5.14.
The tool gives a planning forecast for ovulation after removal of an etonogestrel implant. Fertility may return before the forecast dates. Months to ovulation are approximated by a log-normal distribution with a base median of 1.6 months and a spread parameter (sigma) of 0.42. The median shifts modestly with age, years of use, bleeding pattern while on the implant, BMI band, cycle regularity before the implant, and whether a first bleed has already occurred. Outputs are educational and approximate.
How inputs map to the estimate
- Brand: The available contraceptive implant options in this calculator are treated the same for return to fertility.
- Years of use: +0.10 months per year beyond the first, capped at +1.0 month.
- Age: +0.4 months at 35–39 years, +0.8 months at 40+ years.
- Bleeding while on implant: amenorrhoea +0.3 months, irregular +0.1 months, regular 0 months.
- BMI band: underweight +0.2 months, overweight +0.3 months, obese +0.6 months.
- Pre-implant cycles: irregular +0.5 months.
- First bleed since removal: subtract 1.0 month from the median, floored at 0.5 months.
From months to calendar dates
Months are converted to days using 30 days per month. The middle fifty percent window uses the 25th and 75th percentiles from the log-normal distribution (median and sigma as above). The expected first period window is approximated as ovulation window plus 14 days.
Probability curve and chips
The probability that ovulation has returned by month M is the log-normal cumulative distribution at M. The chips display this cumulative probability for months 1 to 6.
Test date for the forecast
The forecast test date is set to the early ovulation percentile plus 14 days. If that date is in the past, the tool shows “from today if late”.
Care threshold
Suggested review if there is no period by 4 months after removal. At 35 years or older, use 3 months. If a period has already returned, no amenorrhoea threshold is shown.
Limitations
Early cycles can be anovulatory. Breakthrough bleeding can occur before ovulation resumes. The model does not adjust for lactation, thyroid disease, prolactin disorders, or specific medications. All date projections are approximate.
Sources
- ACOG guidance on long-acting reversible contraception, return to fertility after implant removal.
- FSRH guideline on progestogen-only implants, resumption of ovulation and menses after removal.
- CDC Selected Practice Recommendations for Contraceptive Use, counselling on return to fertility.
- Manufacturer prescribing information for etonogestrel implants, rapid return of ovulation after removal.
What each input means
- Removal date: Date the implant was removed. Dates display as 01 Jan 2025.
- Years of use: Total time in place. Used for context in the return-to-ovulation curve.
- Had periods while on implant? Choose amenorrhoea, irregular, or regular. Helps set early-cycle expectations after removal.
- Age: Used for context and care-flag thresholds. BMI band (optional): Context only.
- Cycle regular before implant: Yes/No. Shapes windows if periods have not returned yet.
- First bleed since removal? Select Yes/No and add the date if Yes. A recent bleed suggests ovulation may have resumed.
How to read the results
- Time to ovulation: Median months from removal with an interquartile range (25–75th percentile). Also shows the probability that ovulation has returned by each month.
- First natural period window: A date range for the first period expected after removal, based on the ovulation estimate.
- Test date for this forecast: A date calculated from the forecast ovulation window. You can test sooner according to the missed-period or 21-day guidance below the calculator.
- When to seek care: A care flag if cycles have not returned by the tool’s threshold for your age and history.
- Timeline chart: A simple visual from removal to ovulation and period percentiles.
If periods have not returned and confidence is low, the tool widens windows and suggests when to follow up. This tool is educational only.
Frequently asked questions
How soon can ovulation return after implant removal?
Some people ovulate within weeks. The calculator shows a median and a month-by-month curve for your inputs.
I had no periods on the implant. Does that change return timing?
Amenorrhoea on the implant does not always delay return. Windows adjust based on your history.
Does longer time on the implant change the timeline?
Return can vary. Years of use are included as context in the curve the tool shows.
Do we need to wait for one natural period before trying?
Not required. You can use the likely fertile window before the first period returns.
When should I see a clinician after implant removal?
Follow the tool’s care flag for your age and history. Seek care sooner if you have symptoms.