# Age and fertility > How fertility changes with age in women and men, what tests can and cannot show, when guidelines advise an earlier assessment, and what age means for IVF. Source: https://www.ghinashami.com/en/interests/age-and-fertility/ Updated: 2026-10-13 Step 1 of 4 · Tests Fertility changes with age in women and in men, though not in the same way. This page explains what changes, what tests can and cannot show, and how guidelines take age into account. Its figures are averages and do not predict what will happen for one person. - 5 min read - Reviewed 13 October 2026 - 6 references ## How a woman's fertility changes with age A woman is born with all her eggs: about one million follicles at birth and about 300,000 by puberty, according to the American Society for Reproductive Medicine (ASRM), and the number goes on falling steadily. With age, more of the remaining eggs carry too many or too few chromosomes, and most embryos formed from such eggs do not lead to a pregnancy or end in miscarriage. The decline is gradual: ASRM describes it as slow through the 30s and faster after 35, with wide differences between women. A table in the NICE guideline, from a 2004 study, puts the chance of conceiving within 12 cycles of regular intercourse at 86 in 100 for women aged 30 to 34 and 82 in 100 at 35 to 39. ## What changes for men Men produce sperm throughout life, and NICE describes male fertility as declining with age to a lesser extent than female fertility. A guideline from the American Urological Association (AUA) and ASRM reports small age-related declines in most semen measurements. Less is certain here. That guideline states that there is no clear definition of advanced paternal age, though most studies use 40 and above. As expert opinion, it advises telling couples that some health risks for children are higher from that age, and notes that such a link does not prove cause. See [male infertility](https://www.ghinashami.com/en/interests/male-infertility/). ## What tests can and cannot show No test measures egg quality. AMH and the antral follicle count estimate how many eggs remain: an ASRM committee opinion describes these tests of [ovarian reserve](https://www.ghinashami.com/en/conditions/low-ovarian-reserve/) as testing quantity, not quality, and advises against using them as a test of fertility. NICE advises using a woman's age as the initial guide to her chance of pregnancy, and against using AMH to predict natural conception; see [fertility tests](https://www.ghinashami.com/en/interests/fertility-tests/). ## When guidelines suggest an earlier assessment Guidelines suggest a fertility assessment after a year of trying, and sooner as age rises: - NICE advises referral to a specialist straight away when the woman is 36 or over. - ASRM advises starting the evaluation after six months of trying when the woman is 35 or older. - The American College of Obstetricians and Gynecologists (ACOG) advises six months for women older than 35, and an evaluation before trying to conceive for women older than 40. NICE and ASRM also advise an assessment straight away, at any age, when there is a known reason for concern, such as absent periods. These are points at which doctors look sooner, not advice about when to have children. ## Age and fertility treatment Treatment does not reverse the effect of age on eggs: ASRM states that a woman's age affects the chance of pregnancy with any treatment, [IVF](https://www.ghinashami.com/en/interests/ivf-icsi/) included. In the [HFEA's UK figures for 2023](https://www.hfea.gov.uk/about-us/publications/research-and-data/fertility-treatment-2023-trends-and-figures/), the birth rate per fresh embryo transferred was highest for women aged 18 to 34 and lowest for those aged 43 to 44, using their own eggs. With [egg freezing](https://www.ghinashami.com/en/interests/egg-freezing/), the HFEA notes, the chance of conception depends on the age at freezing and the number of eggs frozen, and freezing does not ensure a baby. Testing embryos for chromosome number ([PGT-A](https://www.ghinashami.com/en/interests/pgt-a/)) selects among the embryos a cycle produces, and NICE advises against offering it to improve live birth rates. General health matters at every age (see [preconception health](https://www.ghinashami.com/en/interests/preconception-health/)): NICE notes that smoking is likely to reduce fertility. ASRM adds that good health does not offset the age-related decline. ## Questions worth asking your doctor 1. 1 How does my age affect the plan? Guidelines treat age as the initial guide to the chance of pregnancy; ask what that means for your options. 2. 2 What can my tests show, and what can they not? AMH and the antral follicle count estimate the number of eggs, not their quality. 3. 3 Should we be assessed now or keep trying? It depends on age, on how long you have been trying and on your history. Dr. Ghina Shami ## Risks and limits **What tests cannot predict.** No test can tell one woman whether she will conceive; ASRM notes that no ovarian reserve test has been shown to predict pregnancy reliably. **Pregnancy at a later age.** Some pregnancy risks rise with age, though not all at once. ACOG notes that miscarriage and stillbirth are more common after 35 and pre-eclampsia after 40, and ASRM that high blood pressure and diabetes develop more often in women who conceive after 35. ACOG adds that the chance of a pregnancy affected by a chromosome condition such as Down syndrome also rises with age, and describes the overall risk as small. **Averages are not individuals.** Every figure here describes a large group; within any age group some women conceive quickly and others do not. Age is one part of the picture, alongside how long a couple has been trying, the semen analysis and each partner's health. ## Common questions **At what age does fertility start to decline?** There is no single age. ASRM describes a gradual decline through the 30s that becomes faster after 35, and ACOG places its start at about 30. The timing varies widely between women. **I am over 35. Will it be hard to conceive?** Not necessarily. In the table NICE quotes, 82 in 100 women aged 35 to 39 conceive within a year of regular intercourse. From 35, ASRM advises an assessment after six months of trying, not a year. **Does IVF make up for age?** No. ASRM states that a woman's age affects the chance of pregnancy with every fertility treatment, IVF included; the HFEA's UK figures show the same. **Evidence basis:** This page is based on guidelines and committee opinions (NICE 2026, ASRM 2020, AUA and ASRM 2024), on ASRM and ACOG patient information and on HFEA national figures; where estimates differ or the evidence is limited, the page says so. ## References 1. Age and fertility (patient education booklet), American Society for Reproductive Medicine (ASRM), ReproductiveFacts.org (2012) — [reproductivefacts.org](https://www.reproductivefacts.org/news-and-publications/fact-sheets-and-infographics/age-and-fertility-booklet/) 2. Fertility problems: assessment and treatment (NICE guideline NG257), NICE (2026) — [nice.org.uk](https://www.nice.org.uk/guidance/ng257) 3. Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy (FAQ060), American College of Obstetricians and Gynecologists (ACOG) (2023) — [acog.org](https://www.acog.org/womens-health/faqs/having-a-baby-after-age-35-how-aging-affects-fertility-and-pregnancy) 4. Fertility treatment 2023: trends and figures, HFEA (Human Fertilisation and Embryology Authority) (2025) — [hfea.gov.uk](https://www.hfea.gov.uk/about-us/publications/research-and-data/fertility-treatment-2023-trends-and-figures/) 5. Testing and interpreting measures of ovarian reserve: a committee opinion (2020), American Society for Reproductive Medicine (2020) — [asrm.org](https://www.asrm.org/practice-guidance/practice-committee-documents/testing-and-interpreting-measures-of-ovarian-reserve-a-committee-opinion-2020/) 6. Diagnosis and Treatment of Infertility in Men: AUA/ASRM Guideline (2020, amended 2024), American Urological Association and American Society for Reproductive Medicine (2024) — [auanet.org](https://www.auanet.org/guidelines-and-quality/guidelines/male-infertility) Written and reviewed by [Dr. Ghina Shami](https://www.ghinashami.com/en/about/), Consultant, Reproductive Medicine and Infertility · 13 October 2026 · [How these pages are prepared](https://www.ghinashami.com/en/legal/#accuracy)