Age is one of the most important factors affecting fertility, but its impact is often oversimplified.
You may have heard that fertility “falls off a cliff” at 35, that men can remain fertile indefinitely, or that a normal AMH result means there is plenty of time to have children. None of these statements tells the whole story.
Fertility changes gradually. For women, age affects both the number and quality of eggs available. For men, age-related changes tend to occur more slowly, but sperm quality and reproductive outcomes can still be affected.
Understanding fertility by age is especially useful for people who are deciding when to start a family, couples who have delayed parenthood, and anyone wondering whether they should seek a fertility assessment sooner rather than later.
There is also an important distinction between population statistics and individual fertility. Knowing what generally happens at 30, 35 or 40 can help with planning, but it cannot tell one person exactly how easily they will conceive.
Here is what actually changes with age and what those changes can mean when planning a pregnancy.
Why Does Female Fertility Decline With Age?
Women are born with the eggs they will have for their reproductive lifetime. That pool naturally declines over time.
But quantity is only part of the story.
As a woman gets older, the proportion of eggs with chromosomal abnormalities also increases. This is why discussions about female fertility by age need to consider both ovarian reserve and egg quality.
The two are related but not interchangeable.
Ovarian reserve refers primarily to the remaining quantity of eggs.
Egg quality is a less precise everyday term that generally refers to an egg’s likelihood of successfully completing fertilization and contributing to the development of a healthy embryo.
There is no routine blood test that directly measures the quality of an individual woman’s eggs.
Tests such as anti-Müllerian hormone (AMH) and antral follicle count can provide information about ovarian reserve, but they should not be interpreted as direct measurements of egg quality or as guarantees of future pregnancy.
Age therefore remains important even when ovarian reserve testing appears reassuring.
The Public Health Agency of Canada’s maternity care guidance notes that female fertility declines significantly beginning in the early 30s, primarily because both the number and quality of available eggs decrease.
Female Fertility by Age: A Practical Timeline
There is no birthday when someone suddenly becomes infertile.
The better way to understand fertility is as a gradual timeline.
Fertility in Your 20s
For most women, fertility is generally highest in the 20s. During this period, ovarian reserve is typically greater and a higher proportion of eggs are expected to be chromosomally normal compared with later reproductive years. Both egg quantity and egg quality decline with age, with the rate of decline becoming more significant in the 30s.
That does not mean pregnancy is automatic.
Someone in their 20s can still experience infertility because of conditions such as:
- Polycystic ovary syndrome
- Endometriosis
- Blocked fallopian tubes
- Uterine abnormalities
- Reduced ovarian reserve
- Ovulatory disorders
- Male-factor infertility
- Unexplained infertility
Age is only one fertility factor.
A 27-year-old who does not ovulate regularly, for example, may have more difficulty conceiving than an older woman with regular ovulation and no identifiable fertility concerns. This is why age should never be used to dismiss symptoms or delay an appropriate fertility assessment.
The 20s may also be an appropriate time to consider egg freezing for those who want to preserve future reproductive options. Eggs frozen at a younger age generally have a higher likelihood of being chromosomally normal than eggs retrieved later in the reproductive years.
As a result, fewer eggs may be needed to achieve a comparable probability of a future live birth when eggs are frozen at a younger age, although individual outcomes vary and no number of frozen eggs can guarantee a future pregnancy.
For individuals considering delaying pregnancy, a fertility assessment can help provide information about ovarian reserve and support a discussion with a fertility specialist about whether and when egg freezing may be appropriate.
Fertility From 30 to 34
The early 30s are often when conversations about fertility become more nuanced.
Many people in Ontario are now starting or expanding their families in their 30s. However, biologically, fertility does not remain unchanged during these years.
For healthy couples, the chance of becoming pregnant naturally during a single menstrual cycle is often estimated at approximately 20–25% in the 20s and early 30s. Fertility then gradually declines through the early 30s, with the decline becoming more pronounced after approximately age 35. These are population-level estimates, however, and individual fertility can vary considerably.
One reason is that both the number and quality of available eggs decline with age. As a woman gets older, a greater proportion of eggs are also expected to have chromosomal abnormalities, which can reduce the likelihood of conception and increase the risk of miscarriage.
For someone who wants several children, this becomes particularly important. The question is not simply, “Can I get pregnant at 32?” It may also be, “If I want two or three children, what does starting at 32 mean for the timing of later pregnancies?”
Time spent trying to conceive, pregnancy itself, postpartum recovery, and spacing between children can add several years to a family-building plan. Someone who has their first child at 33, for example, may be in their mid-to-late 30s when trying for a second or third child.
For people who expect to delay pregnancy or want several children, the early 30s may therefore also be an appropriate time to discuss fertility assessment and egg freezing with a fertility specialist. Eggs frozen at a younger age generally have greater reproductive potential than eggs retrieved later, although individual outcomes vary.
Thinking beyond the first pregnancy is one of the most useful—but often overlooked—parts of reproductive planning.
What Are the Chances of Getting Pregnant at 35?
Age 35 receives enormous attention in fertility discussions.
It is important, but it is not a biological switch.
A woman does not have normal fertility at 34 and suddenly become infertile on her 35th birthday.
Instead, 35 is a useful clinical marker within a decline that has already begun.
By the mid-30s, declining egg quantity and age-related changes in egg quality become increasingly relevant. It may take longer to conceive, and the risk of miscarriage and chromosomal abnormalities also rises with maternal age.
This is why the timeline for seeking professional help is usually shorter after 35.
Canadian maternity-care guidance defines infertility based partly on age: generally after one year of regular unprotected intercourse when the female partner is younger than 35, versus six months when she is older than 35.
That shorter timeline is not meant to suggest that pregnancy at 35 is unusual.
It reflects something practical: when age is becoming a more significant fertility factor, spending another six months waiting before investigating a possible problem may carry a greater opportunity cost.
Fertility From 36 to 39
During the later 30s, age becomes increasingly important when assessing reproductive potential.
Natural fertility declines more noticeably after age 35. While a healthy woman in her 20s or early 30s may have roughly a 20–25% chance of conception per menstrual cycle, estimates are generally closer to approximately 10–15% per cycle by the late 30s, although individual fertility varies substantially.
Egg quality is an equally important part of this change. As reproductive age increases, a larger proportion of eggs have chromosomal abnormalities. This means that even when ovulation is occurring and ovarian reserve appears reassuring, fewer available eggs may have the chromosomal potential to result in a healthy pregnancy.
This distinction between egg quantity and egg quality is particularly important when interpreting AMH.
Two 38-year-old women can have very different AMH levels, reproductive histories and underlying fertility factors. However, a higher AMH level at 38 does not make the eggs biologically equivalent to those of a 28-year-old.
AMH primarily provides information about ovarian reserve the estimated remaining egg supply and likely response to ovarian stimulation. It does not directly measure egg quality. Age remains one of the strongest predictors of the likelihood that an egg will be chromosomally normal.
Age-related changes in egg quality also contribute to an increasing risk of miscarriage as reproductive age advances.
For women aged 36–39 who know they want children particularly those hoping for more than one child there can therefore be value in discussing their reproductive timeline with a fertility specialist sooner rather than waiting until difficulty conceiving becomes apparent.
For those not ready to conceive, a discussion about egg freezing may still be appropriate, but it is important to understand that egg freezing does not reverse reproductive ageing: the reproductive potential of frozen eggs is strongly influenced by the age at which the eggs were retrieved.
Fertility After 40
Pregnancy after 40 is absolutely possible.
At the same time, it is important to discuss fertility after 40 without minimizing the biological changes that occur.
By 40, both ovarian reserve and egg quality have generally declined substantially compared with the 20s and early 30s. The proportion of eggs with chromosomal abnormalities is also higher.
As a result, conception may take longer and miscarriage becomes more common.
This does not mean every woman over 40 requires IVF, nor does it mean natural conception cannot happen.
It means time becomes a particularly important part of fertility planning.
If someone is 40 or older and wants to become pregnant, waiting many months before seeking an assessment may not be the most useful approach. A fertility specialist can evaluate factors such as ovarian reserve, ovulation, uterine anatomy and, when relevant, sperm health to identify issues that could affect the available options.
For Ontario patients, age can also matter when considering publicly funded fertility treatment. The Ontario Fertility Program currently requires patients receiving a funded IVF cycle to be under age 43, in addition to meeting the program’s other eligibility requirements.
Current eligibility and coverage information is available through the Government of Ontario’s fertility treatment program.
Egg Quality by Age: What Does That Actually Mean?
“Egg quality” is used constantly in fertility discussions, but it can be confusing because there is no simple egg-quality blood test.
An egg needs the correct number and arrangement of chromosomes to have the best chance of contributing to normal embryo development.
As women age, chromosomal errors become more common in eggs.
This helps explain several age-related reproductive changes at once:
- Lower probability of conception
- Higher risk that an embryo will not implant
- Higher miscarriage risk
- Increased likelihood of certain chromosomal abnormalities
This is also why ovarian reserve and egg quality must be separated conceptually.
A woman can have a relatively high number of remaining follicles for her age while still experiencing the age-related changes in egg quality associated with that age.
Conversely, a younger woman may have diminished ovarian reserve while her age remains favourable from an egg-quality perspective.
Neither situation can be understood from one number.
Does Male Fertility Decline With Age?
Yes, although the pattern is different from female fertility.
Men continue producing sperm throughout adult life, so there is no direct male equivalent of menopause.
That has contributed to the idea that male fertility does not have an age limit.
Biologically, the picture is more nuanced.
As men age, changes can occur in semen quality and reproductive function. The Public Health Agency of Canada notes evidence that paternal age over 40 may be associated with decreased sperm quality and a slightly increased risk of certain genetic conditions.
Age-related changes may involve:
- Sperm motility
- Semen volume
- Sperm morphology
- DNA integrity
- Sexual function
- Hormonal health
These changes tend to be more gradual and variable than the decline seen in female fertility.
A man in his 40s or 50s may still father a child naturally. But “still fertile” and “fertility is unaffected by age” are not the same statement.
Male Fertility by Age: A Practical Timeline
Men in Their 20s and Early 30s
Age-related decline is generally less of a concern during these years, but younger age does not guarantee normal fertility.
Varicoceles, hormonal conditions, genetic factors, previous testicular injury, infections, medications and other health issues can affect sperm production at any age.
Lifestyle factors can also matter.
Smoking, recreational drug use, heavy alcohol consumption, certain environmental exposures and anabolic steroid or external testosterone use can negatively affect reproductive health.
Men in Their Late 30s and 40s
Age-related sperm changes become more relevant as men move into their 40s.
This does not mean there is a specific birthday when male fertility suddenly drops.
Instead, sperm parameters and reproductive outcomes can gradually change with increasing paternal age.
For couples delaying parenthood, this is an important part of the conversation because reproductive age belongs to both partners.
If a 39-year-old woman and a 45-year-old man are trying to conceive, focusing only on the woman’s age misses part of the fertility picture.
A semen analysis can provide useful information about sperm concentration, motility and morphology, while further testing may be considered when the initial results or medical history suggest it is necessary.
Male Fertility After 50
Many men remain capable of fathering children after 50.
However, that possibility should not be confused with having the same reproductive profile as a younger man.
Age-related changes in sperm and general health may become increasingly relevant, and certain medical conditions or medications are also more common with advancing age.
For an older couple experiencing difficulty conceiving, assessing both partners from the beginning can avoid losing time by assuming that age-related fertility concerns apply only to women.
Can Lifestyle Offset the Effect of Age?
Healthy habits support reproductive and overall health, but they cannot reverse reproductive ageing.
Maintaining a healthy lifestyle may help reduce fertility risks associated with smoking, excessive alcohol use, poor metabolic health or certain environmental exposures.
The Government of Canada’s preconception health guidance encourages both men and women to consider their health, medications, substance use and reproductive plans before pregnancy.
But lifestyle changes cannot make a 40-year-old egg biologically 30 again.
This distinction matters because fertility advice online can sometimes imply that supplements, diet or a particular wellness routine can overcome the reproductive effects of age.
Healthy choices are worthwhile.
They are not a replacement for realistic fertility planning.
When Should You Consider a Fertility Assessment?
Age helps determine how quickly it makes sense to investigate a potential fertility problem.
As a practical starting point:
- Under 35: Consider an assessment after about 12 months of regular unprotected intercourse without pregnancy.
- 35 and older: Consider seeking an assessment after about six months.
- Around 40 and beyond: Earlier discussion with a fertility specialist may be appropriate rather than waiting six to twelve months.
You should also consider earlier evaluation at any age if there are known fertility concerns, such as irregular or absent periods, endometriosis, previous pelvic infections, ovarian surgery, cancer treatment, recurrent pregnancy loss or known male-factor issues.
The point of an assessment is not automatically to begin fertility treatment.
It is to understand whether there is a reason not to keep waiting.
What Can a Fertility Assessment Tell You About Age?
A fertility assessment cannot predict exactly when you will conceive or how many fertile years you have remaining.
It can provide information that makes your age more meaningful in context.
For women, this may include:
- AMH testing
- Antral follicle count
- Menstrual and ovulation history
- Other reproductive hormone testing when indicated
- Ultrasound evaluation
- Assessment of the uterus and fallopian tubes when appropriate
For men, assessment may include:
- Semen analysis
- Medical and reproductive history
- Hormonal or additional testing when indicated
The results help answer a more useful question than “Am I fertile?”
They help determine whether there are identifiable factors, in addition to age, that could affect your chances of conceiving or influence how quickly you should consider treatment.
Should You Freeze Your Eggs Because of Your Age?
Egg freezing can preserve unfertilized eggs for possible future use, but deciding whether and when to freeze eggs is highly individual.
One of the most important factors is age at the time of freezing. If eggs are frozen at 32 and used at 39, they retain the reproductive characteristics associated with the age at which they were retrieved they do not become 39-year-old eggs while in storage.
Age can also influence how many eggs may need to be frozen to reach a similar probability of a future live birth. Because a greater proportion of eggs are expected to be chromosomally normal at younger reproductive ages, someone freezing eggs at a younger age may need fewer eggs to achieve a comparable probability than someone freezing eggs later. As age increases, more eggs may need to be retrieved and frozen to compensate for the age-related decline in egg quality.
This is one reason why discussing egg freezing earlier rather than later can be valuable for someone who expects to delay pregnancy.
Egg freezing, however, is not an insurance policy. Not every frozen egg will survive thawing, fertilize, develop into a viable embryo or result in a live birth. Age, ovarian reserve, desired family size and expected outcomes should therefore be discussed with a fertility specialist when considering whether and when to freeze eggs.
Planning Fertility in Ontario
There is no perfect age to have a child from every perspective.
Education, relationships, career goals, finances, housing, health and personal readiness all influence when Canadians choose to start families.
Biology is only one part of that decision.
But biology is the part that cannot be negotiated later.
Ontario’s own demographic data shows the broader trend toward later childbearing, with more women having children in their 30s and early 40s. That makes accurate fertility education increasingly important.
Understanding age-related fertility is not about pressuring people to have children earlier.
It is about having enough information to make deliberate choices.
For someone who knows they want children but expects to delay pregnancy, a conversation about reproductive planning may be useful before infertility occurs.
For someone already trying, age can help determine how long it makes sense to continue before seeking an assessment.
And for someone who is unsure whether they want children at all, understanding how fertility changes over time can still help keep future options in perspective.
When to Speak With a Fertility Specialist
You do not need to wait until fertility treatment feels inevitable before asking questions.
A consultation may be useful if you have been trying without success, have a known reproductive health concern, are considering delaying parenthood, want to understand ovarian reserve or are thinking about fertility preservation.
For patients in Ontario, Anova Fertility provides fertility assessments, fertility preservation and treatment options for individuals and couples at different stages of family planning.
A specialist can interpret age alongside medical history, ovarian reserve, sperm health and reproductive goals rather than relying on a generic fertility-by-age chart.
That context is what turns population statistics into useful personal information.
The Most Important Thing to Know About Fertility and Age
Age matters, but it does not tell the whole story.
Female fertility generally declines gradually through the early 30s and more significantly as reproductive age advances. The changes involve both the number of remaining eggs and the likelihood that those eggs are chromosomally normal.
Male fertility also changes with age, although usually more gradually. Older paternal age can be associated with changes in sperm quality and other reproductive considerations.
None of this means that pregnancy at 35, 40 or beyond is impossible.
It means that time becomes a more important part of reproductive decision-making.
A 35th or 40th birthday should not be treated as a deadline. At the same time, reassuring test results should not be used to pretend age is irrelevant.
The most useful approach is to consider age alongside your health, reproductive history, partner’s fertility, desired family size and personal timeline.
If having children is important to you, understanding those factors earlier gives you something fertility statistics alone cannot provide: the opportunity to make decisions while you still have more options.
