Female fertility is influenced by many factors, but age is one of the most important. Fertility can also be affected by ovulation problems, conditions involving the ovaries, fallopian tubes or uterus, certain medical treatments, lifestyle factors, and some genetic or hormonal conditions. In some cases, several factors contribute at the same time, while in others no clear cause is identified.
Understanding these factors can help explain why becoming pregnant may be easier for some people than for others and why fertility can change over time.
Age
Age has a major effect on female fertility because both the number and quality of a woman’s eggs change over time.
A female is born with a finite supply of eggs. The number decreases throughout life, and the remaining eggs gradually become more likely to have abnormalities in their chromosomes. This change becomes more significant with increasing age and can make conception more difficult and increase the risk of miscarriage.
Age also affects ovarian function. As the ovaries age, ovulation may become less predictable and eventually stops at menopause. Fertility therefore declines gradually before menopause rather than ending suddenly when menopause begins.
Problems with ovulation
Ovulation is the release of an egg from an ovary. For pregnancy to occur naturally, an egg generally needs to be released and become available for fertilization.
Conditions that interfere with regular ovulation can therefore reduce fertility. Irregular or absent menstrual periods can sometimes be a sign that ovulation is not occurring normally.
Hormonal disorders are among the causes. Polycystic ovary syndrome (PCOS), for example, can interfere with normal ovulation. Other problems involving the thyroid gland, pituitary gland, or reproductive hormones can also disrupt the hormonal signals that control the menstrual cycle.
Very low body weight, substantial weight changes, excessive physical stress, and some other conditions can also interfere with the hormonal system responsible for ovulation.
Conditions affecting the ovaries
The ovaries are responsible for releasing eggs and producing important reproductive hormones. Diseases or abnormalities affecting them can interfere with fertility.
PCOS is a common cause of irregular ovulation. Endometriosis can also affect fertility. In endometriosis, tissue similar to the lining of the uterus grows outside the uterus, potentially causing inflammation, scar tissue, and changes around the reproductive organs.
Ovarian surgery, certain ovarian disorders, and conditions that reduce ovarian function can also affect the ability to conceive.
A reduced ovarian reserve means that the number of remaining eggs is lower than expected. It does not necessarily mean that pregnancy is impossible, but it can reduce the reproductive window and may affect fertility treatment options.
Blocked or damaged fallopian tubes
Fallopian tubes provide the usual location where sperm and egg meet. After ovulation, the egg enters a fallopian tube, where fertilization may occur before the early embryo travels toward the uterus.
If a tube is blocked or damaged, sperm may be unable to reach the egg or the fertilized egg may be unable to travel normally toward the uterus.
Pelvic infections, including some sexually transmitted infections, can cause inflammation and scarring that damage the fallopian tubes. Pelvic surgery and endometriosis can also contribute to scarring or blockage.
Tubal problems may occur without obvious symptoms, so a person may not know there is a problem until pregnancy does not occur.
Problems involving the uterus
The uterus needs to provide an appropriate environment for an embryo to implant and develop.
Fibroids, which are noncancerous growths of uterine muscle, can sometimes interfere with fertility depending on their size and location. Polyps, abnormalities in the shape of the uterus, scar tissue, and other structural problems can also affect implantation or pregnancy.
Not every uterine abnormality causes infertility. Its effect depends on the particular condition and how it affects the reproductive anatomy.
Endometriosis
Endometriosis deserves particular attention because it can affect fertility in several ways.
Endometriosis can cause inflammation and scar tissue within the pelvis. This may alter the normal relationship between the ovaries, fallopian tubes, and surrounding tissues. In more advanced disease, adhesions can distort the reproductive organs or interfere with the fallopian tubes.
The condition can also affect the ovaries and may be associated with changes in ovarian function.
Importantly, the severity of symptoms does not always correspond directly to the degree of fertility problems. Some people with endometriosis have significant fertility difficulties with relatively few symptoms, while others may have substantial symptoms without infertility.
Previous pelvic infections
Some infections of the reproductive tract can cause lasting damage even after the infection itself has gone away.
Pelvic inflammatory disease, which can develop after certain untreated infections, may cause inflammation and scarring of the fallopian tubes and other pelvic structures. This can interfere with the movement of sperm, eggs, or embryos.
Because fertility problems caused by tubal damage may not produce obvious symptoms, preventing and treating reproductive tract infections is important for protecting future fertility.
Body weight and energy balance
Both very low and higher body weight can be associated with reduced fertility in some people.
The reproductive system depends on signals from the brain, ovaries, and other parts of the body working together. Insufficient energy availability can disrupt these hormonal signals and stop or alter ovulation.
Higher body weight can also affect hormonal regulation and ovulation, particularly in people with conditions such as PCOS. Changes in body weight can sometimes improve reproductive function when excess or insufficient weight is contributing to an underlying hormonal problem.
Weight alone, however, does not determine whether someone is fertile. People of different body sizes can have normal or abnormal fertility for many different reasons.
Smoking and tobacco exposure
Smoking can negatively affect female reproductive health. Chemicals in tobacco smoke can contribute to damage involving the ovaries and may accelerate reproductive aging.
Smoking is also associated with an increased risk of problems during pregnancy. Avoiding tobacco is therefore important not only for fertility but also for reproductive health more broadly.
Alcohol and other substances
Alcohol consumption can affect reproductive health, although the relationship between alcohol and fertility depends on the amount and pattern of use.
Other substances can also affect reproductive function. Some recreational drugs may interfere with hormonal regulation, ovulation, or overall reproductive health.
Because substance effects vary considerably, a person’s overall exposure and health circumstances matter rather than any single factor in isolation.
Certain medications and medical treatments
Some medications can interfere with reproductive function. The effect depends on the specific drug, dose, duration of treatment, and the person’s underlying health.
Cancer treatments are a particularly important example. Some forms of chemotherapy and radiation therapy can damage ovarian tissue and reduce ovarian function. The effect can be temporary or permanent depending on the treatment and other factors.
Certain surgical procedures can also affect fertility, particularly when they involve the ovaries, fallopian tubes, uterus, or surrounding pelvic structures.
Anyone concerned about fertility should discuss medications or planned medical treatment with a healthcare professional rather than stopping a prescribed medicine independently.
Chronic medical conditions
Health conditions outside the reproductive system can sometimes affect fertility.
Disorders involving the thyroid, pituitary gland, metabolism, or other hormonal systems can interfere with the signals that regulate ovulation. Some autoimmune diseases and other chronic illnesses may also affect reproductive function directly or indirectly.
Fertility problems can therefore sometimes be a sign of an underlying health condition rather than a problem originating solely in the reproductive organs.
Genetics and chromosome-related factors
Genetic factors can influence reproductive development, ovarian function, and fertility.
Certain chromosome differences or inherited conditions can affect the number or function of eggs, the development of reproductive organs, or the hormones needed for normal reproduction.
Chromosomal abnormalities in eggs also become more common with increasing maternal age. When an egg with an abnormal chromosome number is fertilized, the resulting embryo may have difficulty developing normally or may result in miscarriage.
Stress and fertility
Stress is often discussed as a cause of infertility, but the relationship is more complicated than simply saying that stress prevents pregnancy.
Severe physical or psychological stress can affect the brain’s hormonal signals and, in some circumstances, interfere with ovulation or menstrual cycles. Stress can also affect sleep, eating patterns, sexual activity, and overall health, which may indirectly influence the chances of conception.
Everyday stress, however, should not automatically be considered the explanation for difficulty becoming pregnant. Fertility problems can have many biological causes, and blaming infertility on stress alone can overlook conditions that need medical evaluation.
Sleep and overall health
Sleep and general health can influence the hormonal and metabolic systems involved in reproduction. Poor health, major disruptions in normal routines, and certain chronic conditions may contribute to reproductive problems.
These factors are usually part of a larger picture rather than independent causes of infertility. Maintaining overall health can support reproductive function, but healthy habits cannot eliminate age-related changes or structural and genetic causes of infertility.
The menstrual cycle can provide useful clues
Menstrual patterns can sometimes provide information about reproductive function.
Regular cycles often suggest that ovulation is occurring, although a regular period does not guarantee normal fertility. Irregular, very infrequent, or absent periods may indicate an ovulation or hormonal problem.
Changes in menstrual bleeding, significant pelvic pain, or other unusual reproductive symptoms can also provide clues about conditions such as fibroids, endometriosis, or hormonal disorders.
A menstrual cycle by itself cannot determine whether someone is fertile. Fertility depends on the coordinated function of the ovaries, fallopian tubes, uterus, hormones, and other reproductive factors.
Fertility usually depends on several systems working together
Conception requires several events to occur successfully. An egg must mature and be released, sperm must reach it, fertilization must occur, the resulting embryo must travel through the reproductive tract, and the embryo must successfully implant in the uterus.
A problem at any of these stages can reduce the likelihood of pregnancy.
That is why female fertility should not be viewed as a single measure controlled by one factor. Age, ovulation, ovarian function, fallopian-tube health, uterine anatomy, hormones, genetics, medical conditions, medications, and lifestyle can all play a role, sometimes independently and sometimes together.