# How Long It Takes to Conceive by Age (and When to See a Doctor)

> Month-by-month conception odds, age-stratified fecundity rates from ASRM and the CDC, and the exact evaluation thresholds that tell you when 'trying' should become 'seen by a specialist.'

*Published 2026-06-25 · By Maya Ellison, CNM*

The short answer
For healthy couples having regular, unprotected intercourse, about 85% will conceive within 12 months — but monthly odds fall from roughly 25–30% in your 20s and early 30s, to about 10% or less at age 40. ASRM recommends evaluation after 12 months if you're under 35, after 6 months at ages 35–39, and immediately at 40 or older.

One of the most disorienting parts of trying to conceive is not knowing what "normal" looks like. Is three months a long time? Is six months? The answer depends almost entirely on age — and on a handful of clinical factors that can make the standard timelines irrelevant for some couples. This guide walks through what the data actually say, who the data come from, and what to do with that information in a practical, week-to-week sense.

## What do the numbers say about conception odds by age?

The most frequently cited benchmark comes from [RESOLVE: The National Infertility Association](https://resolve.org/learn/infertility-101/facts-diagnosis-and-risk-factors/), drawing on ASRM data: approximately **85% of healthy couples** will achieve pregnancy within the first 12 months of regular, unprotected intercourse. Within the first three months alone, 30–40% will have conceived.

Those headline numbers mask meaningful age-related variation. The more clinically useful figure is *fecundity* — the probability of achieving a live birth in any given menstrual cycle. Fecundity is the number that shapes how long the process takes in real life, and it declines steadily with age for biological reasons: a smaller total pool of oocytes (a woman is born with all the eggs she will ever have), an increasing proportion of chromosomally abnormal eggs, and gradually declining uterine receptivity.

  Conception Odds by Age: Monthly Fecundity and 12-Month Cumulative Rates

      Age group
      Approx. monthly fecundity (per cycle)
      Approx. 12-month cumulative conception rate
      ASRM evaluation threshold

      Under 30
      25–30%
      ~85%
      12 months of trying

      Age 30
      ~25%
      ~75%
      12 months of trying

      Age 35
      15–20%
      ~66%
      6 months of trying

      Age 40
      ~10% or less
      ~44%
      Immediately upon deciding to try

*Sources: NIH / PubMed Central age-and-fertility review (PMC7721003); ASRM Committee Opinion, October 2023; RESOLVE: The National Infertility Association.*

The declining numbers also carry an important companion statistic: miscarriage risk. For women age 30 or younger, approximately 16% of pregnancies end in miscarriage. By age 40, that figure rises to roughly **27%**. This is not meant to alarm — it is clinically relevant because it means that some couples who do conceive will experience a loss before a confirmed ongoing pregnancy, and that experience should be folded into the broader conversation about timelines.

A note on CDC trends
Even as overall U.S. birth rates have plateaued, birth rates for older women have risen sharply. The [CDC NCHS Data Brief DB556](https://www.cdc.gov/nchs/products/databriefs/db556.htm) reports that the birth rate for women 35–39 reached 54.3 per 1,000 in 2024 — a 5% increase from 2015 — and the rate for women 40 and older climbed 24% over the same period. Delayed parenthood is not merely a cultural trend; it is a measurable demographic reality, and age-stratified fertility counseling has never been more relevant.

## When does "trying" become "time to see a doctor"?

The answer is specific, and it was updated by ASRM in October 2023. In its revised [definition of infertility](https://www.asrm.org/practice-guidance/practice-committee-documents/definition-of-infertility/), ASRM clarified its evaluation timing thresholds — these did not change with the 2023 update, but they remain the clinical standard:

  - **Under age 35:** Seek evaluation after **12 months** of regular, unprotected intercourse without conception.

  - **Ages 35–39:** Seek evaluation after **6 months** of trying.

  - **Age 40 and older:** Seek evaluation **immediately** upon deciding to pursue pregnancy — no mandatory waiting period.

These thresholds are not arbitrary. They are calibrated to the point at which the probability of spontaneous conception in the next cycle drops low enough that an evaluation provides more value than continued unassisted trying. Importantly, seeking an evaluation does not commit anyone to treatment. It simply provides information — and information, in a field where early intervention often matters, is valuable.

Equally important: ASRM specifies that evaluation should begin *sooner* than these thresholds if certain clinical risk factors are already known. Both ASRM and [ACOG Committee Opinion No. 762](https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2019/01/prepregnancy-counseling) recommend prompt evaluation for couples with:

  - Irregular, infrequent, or absent periods — which can signal ovulatory dysfunction, identified in up to **40% of women with infertility**

  - Known or suspected uterine fibroids, polyps, or adhesions

  - A history of pelvic inflammatory disease, prior ectopic pregnancy, or endometriosis

  - Prior cancer treatment (chemotherapy or radiation) that may have reduced ovarian reserve

  - Family history of premature ovarian insufficiency or early menopause

  - A male partner with known risk factors: prior cancer treatment, a history of undescended testicles, testicular injury, mumps orchitis, or prior vasectomy

That last point deserves emphasis: **male factors are identified in approximately 40% of diagnosed infertility cases** — either as the sole cause or a contributing factor. In roughly one-third of all cases, male infertility alone is responsible, per ASRM. A complete evaluation therefore always includes semen analysis for the male partner, not only hormonal testing for the female partner.

## What modifiable factors actually influence how quickly you conceive?

Age-related egg quality decline is not reversible, but where any individual lands within the population-level statistics for their age is meaningfully influenced by lifestyle, nutrition, and a few emerging clinical interventions.

**Diet quality.** A 2023 systematic scoping review published in *Human Reproduction Update* found that a **Mediterranean dietary pattern** — high in olive oil, vegetables, legumes, fish, and nuts, and low in processed meat and refined carbohydrates — showed the strongest and most consistent association with improved clinical pregnancy rates among all dietary variables studied. The protective effect held even in women undergoing assisted reproductive technology (ART). A companion 2024 systematic review found improvements in semen quality parameters as well, making this a two-person preconception intervention.

**Omega-3 supplementation.** A study published in *Human Reproduction*, analyzing 900 women across 2,510 menstrual cycles, found that women taking omega-3 supplements had **1.83 times the probability of conceiving** in any given cycle compared with non-users. Omega-3s also appear to improve semen quality parameters.

**Timing intercourse within the fertile window.** The fertile window is approximately six days long, ending on the day of ovulation. Intercourse in the two to three days before ovulation — when cervical mucus is most sperm-receptive — produces the highest per-cycle conception probability. Ovulation predictor kits (OPKs) detect the LH surge that typically precedes ovulation by 24–36 hours. For women with irregular cycles, identifying the actual fertile window requires more tracking effort and may signal underlying ovulatory dysfunction worth discussing with a provider.

**Folic acid or methylfolate, started now.** ACOG recommends 400 mcg of folic acid daily, beginning *at least one month before conception* — ideally three months — and continuing through the first trimester. The neural tube closes in the first 28 days after conception, often before a positive test. Women with MTHFR gene variants may benefit from the methylated form (5-MTHF) rather than synthetic folic acid; a qualified practitioner can discuss whether testing and supplementation adjustments are appropriate.

**A note on luteal-phase support.** For couples who have confirmed ovulation but are experiencing difficulty sustaining early pregnancies, luteal-phase progesterone insufficiency is one correctable root cause. The 2025 PiNC Trial — published in *BJOG* — found that vaginal micronized (bioidentical) progesterone at 400 mg twice daily during the luteal phase more than doubled live birth rates in women with unexplained infertility compared with expectant management alone (15.3% vs. 7.0%), though the trial was underpowered and a larger confirmatory study is warranted. This is not a self-directed intervention; decisions about progesterone supplementation should always involve a qualified physician.

*This article is general health information, not a substitute for personalized medical advice. If you have concerns about your fertility or have been trying to conceive, please speak with your OB-GYN, certified nurse-midwife, or reproductive endocrinologist.*

## Sources

1. [Facts, Diagnosis, and Risk Factors](https://resolve.org/learn/infertility-101/facts-diagnosis-and-risk-factors/)
2. [Definition of Infertility: A Committee Opinion (2023)](https://www.asrm.org/practice-guidance/practice-committee-documents/definition-of-infertility/)
3. [Knowledge about the impact of age on fertility: a brief review](https://pmc.ncbi.nlm.nih.gov/articles/PMC7721003/)
4. [FastStats — Infertility](https://www.cdc.gov/nchs/fastats/infertility.htm)
5. [A Decade of Changes in State Fertility Rates for Women Age 30 and Older: United States, 2015–2024](https://www.cdc.gov/nchs/products/databriefs/db556.htm)
6. [Fertility Evaluation of Infertile Women: A Committee Opinion (2021)](https://www.asrm.org/practice-guidance/practice-committee-documents/fertility-evaluation-of-infertile-women-a-committee-opinion-2021/)
7. [Prepregnancy Counseling, Committee Opinion No. 762](https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2019/01/prepregnancy-counseling)
8. [Progesterone Luteal Support in Natural Cycles for Unexplained Infertility: The PiNC Trial](https://pmc.ncbi.nlm.nih.gov/articles/PMC12232507/)

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