Estimate when ovulation may return after birth using feeding patterns and cycle status. See LAM eligibility, probability by month, first fertile window, earliest reliable test day, and when to consult.
Methodology & Sources
What this estimates
The tool provides educational estimates for return of ovulation after birth. It reports: LAM eligibility, probability that ovulation has returned at the baby’s current age, a median month for ovulation with an interquartile range, a window for the first period, an earliest reliable pregnancy test day, and a simple month by month curve.
Evidence base in brief
Breastfeeding intensity and pattern suppress ovulation through hypothalamic pituitary mechanisms. Exclusive or nearly exclusive feeding with night feeds is associated with a lower early return of ovulation. LAM is considered reliable for pregnancy prevention during the first 6 months when all criteria are met. When any criterion is not met, protection falls. Postpartum bleeding patterns vary with feeding, maternal age, and medical factors.
Model overview
- Suppression score: a 0 to 1 scale from feeding exclusivity, night feeds, feeding method, and current contraception. Higher values indicate greater ovulatory suppression.
- Return to ovulation curve: a logistic curve parameterised by a median month (
m50) and a spread parameter (k). The median increases with stronger suppression and modestly with older maternal age and reported complications. - IQR: the 25th and 75th percentile for month of ovulation is
m50 ± 1.099 × k. This gives a middle fifty percent band. - First period window: ovulation percentiles shifted by about 14 days to reflect a typical luteal phase. Individual luteal lengths vary.
- Earliest test day: about 10 days after the early edge of the ovulation window. If a first period has already returned, the next cycle estimate is used instead.
LAM eligibility logic used here
- Baby age under 6 months.
- No return of menses since birth.
- Fully or nearly fully breastfeeding (about 90 percent or more of intake).
- At least one night feed.
- Primarily direct breastfeeding rather than pumping only.
If all are met, the tool shows “Meets LAM criteria while these conditions continue.” If any fail, it lists which ones and does not count LAM as reliable.
How inputs map to outputs
- Exclusivity, night feeds, feeding method: increase the suppression score, which shifts the median month later and widens the spread slightly.
- Contraception: progestin only methods or a hormonal IUD increase suppression in the model. Combined pills increase suppression more and can alter bleeding patterns.
- Maternal age: adds a small delay from 35 years, a larger delay from 40 years.
- Complications: adds a small delay and widens uncertainty.
- Baby age: used to calculate probability that ovulation has returned by now from the curve.
Care threshold
The tool suggests a month to seek review if no period has returned. Thresholds are earlier with lower suppression patterns and at older maternal ages, and later with strong exclusive feeding. This is general guidance only. Seek care sooner for concerning symptoms or if advised by a clinician.
Limitations
- Educational model, not a clinical prediction. Individual variation is large.
- Does not diagnose ovulation. Temperature charts, cycles, and clinical advice are needed for confirmation.
- Medical conditions, medicines, and pumping schedules can change bleeding and ovulation patterns in ways not fully captured here.
Sources
- Family Planning: A Global Handbook for Providers — LAM (criteria and effectiveness while criteria are met).
- ACOG — Postpartum birth control (postpartum contraception and LAM patient guidance).
- FSRH — Contraception after pregnancy (UK guidance on postpartum contraception and return of fertility).
- WHO, LAM counselling materials and related breastfeeding guidance on fertility suppression.
What each input means
- Baby age (months): Age at the time you use the tool. Drives the return curve.
- Feeding pattern: Enter exclusivity percent, number of night feeds, and pumping vs direct. Used to assess LAM and shape timing.
- Postpartum menses returned? Select Yes/No and add the date if Yes. A period suggests ovulation has likely resumed.
- Birth type: Vaginal or C-section. Complications affecting cycles (optional): Logged for context.
- Current contraception: Choose LAM met, not met, or other. The tool checks which LAM criterion fails if not met.
How to read the results
- LAM eligibility: Yes/No with a note showing which criterion fails (baby age, feeding frequency/exclusivity, or menses returned).
- Probability ovulation has returned: Chance at your current month. If not returned, a month-by-month curve shows the rising probability.
- If menses returned: Typical time to more regular cycles and the likely first fertile window.
- Earliest reliable pregnancy test day: The first day many home tests are more reliable based on your period window.
- When to consult: A prompt to seek care if cycles have not returned by the tool’s threshold or if you have concerns.
Ovulation can occur before the first period postpartum. Feeding changes, illness, stress and sleep patterns can shift timing. This tool is educational only.
Frequently asked questions
How is LAM eligibility decided?
The tool checks common criteria: baby age, no periods, and exclusive or near-exclusive feeding with night feeds. It shows which criterion fails if LAM is not met.
Can I ovulate before my first period postpartum?
Yes. Ovulation can precede the first period. The curve shows how probability changes with baby age and feeding.
Do pumping or fewer night feeds affect LAM?
They can. Lower exclusivity or longer gaps overnight may reduce LAM protection, so the tool flags LAM as not met when thresholds are not met.
How should I time a pregnancy test postpartum?
Test after your expected period window. If cycles are not yet regular, use the first likely window shown.
When should I see a clinician?
Use the care prompt in your result. Seek advice earlier if you have symptoms or concerns.