Estimate how soon ovulation and a first period may return after stopping combined or progestin-only pills. See likely fertile windows for the first two cycles, cumulative chances at 3, 6, and 12 months, and the earliest reliable test day.
Methodology & Sources
What this estimates
The tool gives educational estimates for time from the last pill to the return of ovulation and menses, then projects a simple trying-to-conceive timeline. It reports: a median and interquartile range for months to ovulation, the probability that ovulation has returned by the current date, an expected first period window, two early fertile windows, cumulative chance of pregnancy at 3, 6, and 12 months (assuming sex 2–3 times per fertile window), an earliest reliable test day, and a care threshold date if periods have not resumed.
Model outline
- Return to ovulation: months-to-ovulation is modelled with a log-normal distribution.
- COC vs POP: combined pills use a slightly longer median than progestin-only pills, reflecting typical washout patterns.
- Modifiers: age band, months of continuous use, BMI band, and pre-pill cycle regularity shift the median by small amounts.
- Withdrawal bleed: reporting a withdrawal bleed after stopping reduces the median modestly.
- First period: expected around 14 days after ovulation windows, displayed as a date range.
- Pregnancy chances: monthly fecundability is age-based; cumulative chance assumes independent cycles and regular timing during the fertile window.
How inputs map to outputs
- Pill type: COC median starts at about 1.5 months; POP median starts at about 1.1 months. Spread parameter is moderate, yielding a middle fifty percent about 0.7Ă— to 1.4Ă— the median.
- Months of use: a shallow slope beyond 6 months adds roughly 0.02 months per extra month, capped.
- Age: small additions from 35 years, larger from 40 years.
- BMI band: underweight, overweight, and obese add small steps to the median.
- Pre-pill irregular cycles: adds a modest delay and lengthens cycle spacing for the second fertile window.
- Withdrawal bleed: subtracts a small amount from the median; does not force ovulation to have occurred.
- Probability “ovulating by now”: cumulative probability from the log-normal at months since the last pill.
- Fertile windows: a 5-day window centred on the median ovulation date, then a second window one cycle length later (28 days if regular, 30 days if irregular).
- Cumulative chance at 3/6/12 months: uses age-based per-cycle fecundability and combines across the number of cycles spanned by those months.
- Earliest reliable test: ten days after the early bound of the ovulation window.
- Care threshold: review if no period by about 3 to 4 months, earlier for older ages and POP users.
Assumptions and bounds
- Dates display in the format “01 Jan 2025”.
- Medians and ranges are educational. Clinic protocols and diagnoses vary.
- Per-cycle fecundability is age-based and capped within plausible limits.
- Independence between cycles is assumed for cumulative chance; real-world dependence can change results.
- Outputs are clamped to keep values within plausible clinical ranges.
When to seek care
If no period has returned by the displayed threshold, consider a review. Seek earlier care with pain, heavy or unusual bleeding, or if you have specific clinical concerns.
Limitations
- Does not account for smoking, thyroid disease, hyperprolactinaemia, or other medical factors.
- Does not substitute for clinical evaluation. Educational use only.
Sources
- ACOG — Combined hormonal birth control (return of fertility after discontinuation).
- CDC — U.S. Selected Practice Recommendations for Contraceptive Use (guidance on discontinuation and return to fertility).
- FSRH clinical guidance (UK Faculty of Sexual & Reproductive Healthcare; combined and progestin-only contraception, return to fertility).
- WHO — Selected practice recommendations for contraceptive use (global guidance on starting and stopping methods).
- ASRM Committee Opinion: female age-related fertility decline (age and per-cycle fecundability context).
What each input means
- Pill type: Combined oral contraceptive (COC) or progestin-only pill (POP). Results are stratified by type.
- Last pill date: The date you stopped taking pills. Dates display as 01 Jan 2025.
- Months of continuous use: Total time on pills before stopping. Used for context in return-to-ovulation timing.
- Withdrawal bleed occurred? Select Yes/No and add the date if Yes. A withdrawal bleed is not a natural period but can help anchor timing.
- Age: Used for context. BMI band (optional): Additional context only.
- Cycle regularity before pills: Regular or irregular. Helps set expectations for early cycles after stopping.
How to read the results
- Time to ovulation and first period: Median and interquartile range from the stop date, shown separately for COC and POP.
- Fertility timeline (first two cycles): Likely fertile windows plotted for Cycle 1 and Cycle 2.
- Cumulative chance of pregnancy: Estimated chance by 3, 6, and 12 months, assuming sex 2–3 times per fertile window.
- Earliest reliable test day: The day after the first expected period window ends. Follow the test pack instructions.
- POP notes: Hormone washout is often shorter and cycles can be irregular at first. Windows may be wider.
If there is no clear timing signal, the tool widens windows and may suggest logging OPKs or BBT. This tool is educational only.
Frequently asked questions
Do I need a withdrawal bleed before I can ovulate?
No. Ovulation can occur before any bleed after stopping, especially with POP.
Are early cycles irregular after stopping?
They can be, particularly after POP. The tool widens windows if irregularity is likely.
Does longer use delay return?
Some people return quickly regardless of duration. The model uses your use-length as context but individual timing varies.
How should we time sex in the first cycles?
Use the fertile windows shown. Many aim for 2–3 acts across each window.
When should I take a pregnancy test?
After your first expected period window ends. The tool shows the first reliable day to test.