A female’s life stage and the presence of various health conditions affect the fertility rates.
This article explores a female fertility at different stages of the life.
We also discuss tests to measure egg count, fertility options, conditions that may impact eggs, and more.
While females have millions of eggs in their ovaries, they do not mature until puberty.
Puberty begins when the hypothalamus, an area of the brain that plays a role in hormone production, produces the gonadotropin-releasing hormone (GnRH).
Menstruation typically begins when a female is 12–13 years old.
However, some may start as early as 8 years old.
A female typically has around 300,000–500,000 eggs when puberty begins and rapidly loses more eggs each month.
Aside from their monthly cycles, many factors affect how many eggs a person loses every cycle.
The GnRH regulates the onset of puberty, sexual development, egg development, and ovulation by signaling the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
The FSH activates several immature eggs in fluid-filled sacs called follicles to mature during each menstrual cycle.
Known as the follicular phase, this process begins on the first day of a person’s period.
The ovulation phase begins when the LH stimulates the ovaries to release an egg.
However, the ovaries are programmed to allow only one egg to fully mature and be released each cycle.
The body reabsorbs the rest.
The chance of fertilization is dependent on the release of a mature egg from the ovary in a particular menstrual cycle.
A female is most fertile in their mid-20s, with a 25–30% chance of becoming pregnant each month.
ACOG states that a female’s fertility gradually and significantly drops around age 32. They will have around 120,000 eggs, with a 20% chance of conceiving per cycle.
ACOG further states that a female will experience a rapid decline by age 37, when egg count drops to around 25,000.
According to the Centers for Disease Control and Prevention (CDC), around 1 in 5 couples where the female partner is 30–39 years old experience problems conceiving their first child. However, both males and females may experience infertility.
By 40, a female’s chance of conceiving drops to 5%.
Older females generally have a lower success rate with fertility treatments such as in-vitro fertilization (IVF).
However, more people are successfully conceiving in their 40s.
The number of births in women between 40–44 years old rose almost continuously from 1985 to 2019.
There was a slight decline in birth rates in 2020 across all age groups.
Using eggs donated by younger females increases the chance of success with IVF for older females.
By the time a female reaches menopause, they may have fewer than 1,000 eggs.
As a person ages, immature eggs become increasingly resistant to the FSH. As the number of viable eggs decreases, the ovaries also begin to produce significantly less estrogen and progesterone.
This leads to menopause, when a person’s menstrual cycle ends and they no longer ovulate.
The average age a person reaches menopause in the United States is 52 years.
This varies depending on how many eggs a person has at birth and other factors, such as medical conditions and treatment.
Aside from decreasing in number, eggs also drop in quality as a person ages.
A few hours before ovulation, the oocyte divides, resulting in an egg that contains 23 chromosomes.
Older age is highly associated with oocyte abnormalities.
These older eggs are more likely to contain abnormal chromosomes.
This is why the risk of having a child with Down Syndrome and other abnormalities is higher as a person ages.
This tendency to have extra or missing chromosomes is also responsible for the increased miscarriage and low birth rates among older adult females.
There are tests that a person can take to estimate their egg count.
Antral follicle count
The antral follicle test involves a medical practitioner using ultrasound to count visible follicles.
This gives them an idea of a person’s total egg count and how many eggs a person can potentially freeze during one cycle.
Anti-Mullerian hormone (AMH) test
The anti-Mullerian hormone (AMH) is a protein hormone produced by special follicular cells.
The AMH level in the blood can help healthcare professionals estimate the number of follicles in a person’s ovaries, which gives them an idea of their total egg count.
Since AMH levels are stable throughout the menstrual cycle, a doctor can perform this test at any time.
There are several options a person may consider to improve their chances of pregnancy.
Older people or those who have premature ovarian failure (POF) that causes early menopause may consider egg donation.
This involves using eggs donated by another female, typically someone in their 20s or early 30s.
In an egg donation cycle, a donor takes medications to stimulate the production of multiple eggs.
At the same time, the recipient undergoes hormone therapy to prepare the uterus for pregnancy.
After the donor’s eggs are fertilized in a laboratory, a doctor places one or more embryos into the recipient’s uterus.
Egg freezing or fertility preservation
Individuals who want to delay childbearing may consider preserving their healthy eggs in a process known as egg freezing.
A doctor can extract the eggs while the person is younger and use when they want to become pregnant.
The process involves taking medications to stimulate the ovaries to produce multiple eggs.
These eggs are retrieved and kept in a laboratory at sub-zero temperatures.
When a person is ready to conceive, a doctor thaws the eggs and injects surviving eggs with a partner or a donor’s sperm for fertilization.
Assisted reproductive technologies
People with unexplained infertility, or when traditional options have failed, may try more advanced therapies.
These can include IVF and superovulation with timed intrauterine insemination (IUI).
In superovulation and IUI, a female takes medications to stimulate the growth of multiple eggs in the ovaries.
When the eggs are ready to ovulate, a donor or partner’s washed sperm is injected directly into the uterus.
Sometimes an additional medication is given to stimulate ovulation so that timing is more certain.
In contrast, IVF involves removing a person’s egg that a doctor fertilizes with a donor or partner’s sperm in a laboratory. Once successful in fertilization, the doctor transfers the embryo to the uterus.
Most information about egg supply and fertility options is for cisgender and heterosexual females.
However, fertility issues can affect anyone born with ovaries.
A person transitioning to male can freeze their eggs, embryos, or ovarian tissue before hormone therapy or gender-affirmation surgery.
People assigned female at birth (AFAB) and taking the male hormone testosterone may experience amenorrhea, the absence of menstruation due to the hormone suppressing ovulation.
The effect of taking testosterone on egg supply is unclear.
But a recent small study found that functional ovarian reserve was preserved in transgender men receiving testosterone therapy over a prolonged period.
A case study from 2020 documented a person taking testosterone who was able to retrieve eggs for freezing.
They stopped testosterone treatment for only 24 days around the time of egg stimulation.
This compares to cases where hormone treatment ceased for up to 6 months before egg retrieval.
Another case study from 2019 reported a 20-year-old transgender male becoming pregnant 2 months after stopping testosterone therapy.
More research is needed to offer accurate fertility guidance to trans people.
A person wishing to discuss their fertility options before or after transitioning should speak with a medical professional.
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Age is the major factor that affects a female’s egg quality.
However, some conditions may also contribute, including:
A 2017 study found that oxidative stress damages oocytes and impairs their fertilization capacity.
Smoking, drinking, drug use, and inadequate diet can increase free radicals in the body, damaging the egg.
According to the CDC, medical professionals recommend that females younger than 35 years with no health or fertility issues and regular periods try to conceive for at least 1 year before consulting a doctor.
However, females 35 years or older should contact a doctor after 6 months and even sooner for those over 40 years old.
People who have other health issues or circumstances such as irregular periods or have received chemotherapy should also consider discussing their fertility options sooner.
A person’s biological clock affects their fertility.
Age not only decreases fertility rates but can also affect eggs quality.
People concerned about their egg supply due to factors such as aging, different priorities, gender-affirming surgery or hormone therapy, or preparation for cancer treatment have several fertility options to consider.
A person should discuss these options with a healthcare professional to determine which options are most suitable.
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