“The biological clock” is a phrase in reproductive health, and it is also one of the most misunderstood. The link between age and fertility changes slowly and unevenly for both men and women, and the pattern is different for each person. Here is what really changes, when it is wise to get checked, and what the tests can and cannot reveal.
Most people know that fertility gets lower as you get older. What is not as clear is how it gets lower, why that happens, and what that means in life. The idea of a “clock” suggests a time limit; the truth is more like a slow change with a lot of differences between people. Knowing this won’t make choices about when to have children simple. It gives you better information to make those choices.
What Actually Changes in Women: Egg Quantity and Egg Quality
Women are born with all the eggs they will ever have, and over time the number gets smaller and smaller. As people get older, two things happen: the amount of eggs left, which is often called “reserve,” and the quality of the eggs, meaning how likely each egg is to have the correct number of chromosomes. I have seen that when egg quality is lower, the chance of conceiving in each cycle goes down and the chance of miscarriage goes up. Egg quality usually declines slowly through the thirties, and the decline in egg quality becomes more obvious from the mid-thirties onward. The speed of this decline in egg quality is different, for each woman. Age is not the factor. Things like endometriosis, polycystic ovary syndrome, and thyroid problems block fallopian tubes. Past surgery and smoking can all influence how fertile a person is, no matter what age they are.
What About Men? Sperm Quality and Age
Men do not have an end to fertility, but fertility is not constant either. Sperm quality, including sperm movement and sperm DNA integrity, can decline gradually with age, and the time to conceive can lengthen. Because male factors contribute to a share of fertility difficulties, both partners should be assessed, not just the woman. (See our article on male infertility.)
| Myth | What’s closer to the truth? |
|---|---|
| “Fertility falls off a cliff on a specific birthday.” | It declines gradually and varies a lot between individuals. Some people have difficulty earlier, others later. |
| “If my cycles are regular, my fertility is fine.” | Regular periods are a good sign but don’t tell you about egg quality or other factors such as blocked tubes. |
| “Age only matters for women.” | Male fertility is also affected by age, and male factors contribute to a large share of cases. |
| “I look and feel young, so I’m fine.” | General health and appearance don’t reliably reflect egg quantity or quality. |
| “IVF can overcome any age-related problem.” | IVF can help many people, but it doesn’t reverse age-related changes in egg quality, and success rates are affected by age. |
When to get checked
A common guide that is said to come from the American Society for Reproductive Medicine is to get help after 12 months of trying and not getting pregnant if you are, under 35. If you are 35 or older the advice is to get help after 6 months of trying and not getting pregnant. Many experts suggest seeing a doctor preferably before you start trying for a long time if you are over 40 have periods that are not regular or are missing completely known issues like endometriosis or polycystic ovary syndrome, a past history of pelvic infections or surgery or if you know your partner has a semen problem. If you are not ready to try now but want to learn about your choices, a visit, to a healthcare provider can help you prepare.
What fertility tests can and can’t tell you
- History and examination for both partners
Cycle pattern, medical and surgical history, previous pregnancies, lifestyle, and, for men, general health and any previous testicular or urinary conditions.
- Ovarian reserve tests
A blood test for anti-Müllerian hormone (AMH) and an ultrasound count of resting follicles estimate the number of eggs remaining. A reproductive endocrinologist can interpret them. They describe quantity, not quality, and a low or high result on its own doesn’t predict whether you will conceive naturally.
- Checking ovulation, uterus and tubes
Hormone tests, pelvic ultrasound, and where appropriate a test to check the fallopian tubes are open.
- Semen analysis
A simple, non-invasive test of sperm count, movement and shape. It is an essential part of any fertility assessment.
Options if you’re thinking ahead
- Timing and planning: a fertility consultation helps you understand your situation instead of trusting general statistics.
- Treating conditions is key, to improving fertility. Treating conditions can help fix some causes of reduced fertility. For example thyroid problems or ovulation disorders can be treated.
- Assisted treatments: these range from medicine that helps with ovulation, to placing sperm inside the uterus, to in vitro fertilization. Which one works best depends on the reason for the difficulty and on the person.
- Egg freezing: some women decide to freeze eggs when they’re younger to keep choices open. It does not guarantee a future pregnancy, and results are usually better when the woman is younger at the time of freezing. Rules on egg freezing vary by country, so it is worth discussing with a specialist.
A note on this topic
Questions about age and fertility can carry a lot of emotion, including worry, pressure, grief, or a sense of being behind. None of those feelings is unreasonable. You don’t need a “good enough reason” to ask for an assessment, and support, including counselling, is part of good fertility care.
Frequently asked questions
Q: Can I tell how fertile I am from my age alone?
No. Age is a factor but age can differ a lot. Age alone does not give a picture. Testing and a clinical assessment give a more personal picture, than age alone.
Q: Does a low AMH mean I can’t get pregnant?
Not necessarily. AMH indicates the number of eggs remaining not the quality of those eggs and on its AMH does not predict whether you will conceive naturally. AMH is more useful, for planning fertility treatment. Amh should be interpreted by a specialist.
Q: Does a man’s age matter?
Yes I think the change is usually more gradual than it is, in women. Sperm quality can decline as a person gets older and any assessment of sperm quality should involve both partners.
Q: Is IVF the only option if I’m older?
No. Depending on the cause, simpler treatments might be the first step. Ask the specialist about the options that fit your situation and what you can realistically expect. For women whose own eggs are unlikely to succeed, donor egg treatment is another option.
Q: Can I get a fertility opinion before deciding on treatment abroad?
Yes. Our partner fertility specialists can review your reports through a no-obligation second-opinion consultation. This way you can fully understand your situation and your options before you make any decisions.
Conclusion
The biological clock is real. The biological clock is a slope with a lot of individual variation, not a deadline with a date. I think the useful thing you can do is replace general numbers with your own information: a check for both partners’ honest answers about what the results mean and enough time to make decisions that are right for you.