Male & Female Fertility Explained: What Factors Can Affect It?

By BSc, MSc (embryologist), MD, PhD (gynecologist), PhD, MSc (senior embryologist) and BA, MA (fertility counselor).
Last Update: 10/25/2016

Human fertility can be described as the capacity of both the male and the female to procreate. Sometimes, and for a number of reasons, this natural capacity can be hindered and make them have trouble conceiving, either because of male infertility, female infertility or a combination of both.

When is it time to see a fertility specialist?

When a couple is unable to achieve pregnancy successfully after a year trying to conceive, that is, having unprotected sexual intercourse, we can consider the possibility that there exists a fertility problem and it may be time for the couple to see a fertility specialist.

On the other hand, it should be clear that infertility and sterility cannot be used synonymously. They both refer to the inability to have offspring, but from two different points of view. While infertility is the inability to give birth to a healthy baby, sterility is defined as the impossibility to conceive.

Thanks to the latest advancements in the field of reproductive medicine, today several analyses and fertility tests can be carried out to detect infertility and sterility, as well as to determine the appropriate treatments to struggle with infertility and have a baby.

Male fertility

Male fertility is directly linked to sperm quality, specifically on each one of the spermatozoa it contains. Several parameters have an impact on sperm quality, especially sperm concentration, sperm motility and sperm morphology.

Age can affect male fertility by reducing sperm quality, although not as sharply as in the case of female fertility. It has been proven that the seminal volume decreases slowly, yet progressively, over time due to age-related changes in the seminal vesicles.

Likewise, the number of sperm with normal motility diminishes, while the presence of oxidative stress increases, which is a major causative factor for sperm DNA damage. The chances for the sperm to have a genetic abnormality are higher as men get older.

Poor sperm quality can lead to the appearance of the following pathologies:

There exist no male infertility symptoms. We can suspect that there may be a fertility issue when the couple experiences trouble conceiving or is unable to carry a pregnancy to term, though. In such case, both members of the couple should be tested to determine the specific cause.

The causes of male infertility can be classified into:

  • Testicular diseases: varicocele, orchitis or orchiditis, cryptorchidism, hydrocele, testicular trauma, etc.
  • Male hormone imbalances: due to an hypothalamic dysfunction or endocrine disorders in men.
  • Disorders of the seminal ducts: ejaculatory duct obstruction (EDO), retrograde ejaculation, etc.
  • Sperm-related issues: abnormalities of sperm linked to parameters such as concentration, motility, morphology and vitality causing poor sperm quality, as explained earlier.

Female fertility

Female fertility is directly associated with a woman's egg supply and quality. The extent to which the uterine lining is prepared for embryo implantation and the proper development of a pregnancy is a key factor as well.

The production and maturation of oocytes is determined by sex hormones and the menstrual cycle, which is regulated by estrogens, progesterone, FSH and LH. Each one of them has its own function.

On the one hand, estrogens and FSH trigger the development of the follicles containing the eggs. On the other hand, LH maintains its levels until the egg is mature, and it is in that moment when it increases its levels, reaching a LH surge that triggers ovulation. Progesterone, however, prepares the endometrial lining so that the embryo can implant if fertilization occurs.

Women can find out what their fertile days are by calculating their date of ovulation. To do so, the counting should start on the 14th day from the first day of the last period, since ovulation occurs halfway through the cycle, which is to say, around day 14 as long as it is a regular 28-day cycle.

A woman's fertile days are the ones closer to ovulation, that is, the release of a mature egg. The menstrual cycle is comprised of the day of ovulation and the days immediately before and after that date.

Ovulation calendars are useful when it comes to determining the ideal moment to engage into sexual intercourse for trying to get pregnant. Also, ovulation tests can be helpful for women with irregular menstrual cycles or if they want to make sure they are actually on their fertile days.

It should be taken into account that a woman's fertile period is limited and dependent on age to a large extent. The age factor has an impact on the egg reserve, that is to say, the amount of eggs contained within the ovary. From age 35-37 onwards, it diminishes substantially, which at the same time reduces the odds for achieving a successful pregnancy.

Women experiencing trouble getting pregnant should have their fertility levels checked. Fertility tests are the only way to determine what is causing infertility, as there exist no symptoms of female infertility or sterility.

Female infertility is not always caused by a diminished egg supply, though. Other causes may be:

  • Problems with ovulating
  • Disorders of the cervix, either functional or anatomical
  • Tubal factor infertility: if the woman has no Fallopian tubes, or if they are blocked or have congenital malformations
  • Uterine abnormalities: malformations, endometriosis, myomas, polyps, etc.

Fertility testing for couples

In principle, the cause of infertility can be detected by assessing the couple's fertility levels. By doing this, the potential infertility problem can be addressed through the reproductive treatment that guarantees the best chances for success. Even though the problem may have a male or female origin, infertility is a two-way thing and affects both partners.

Unexplained infertility or idiopathic infertility is the cause in 15% of the cases. It is diagnosed when fertility tests do not show a specific infertility problem, yet pregnancy cannot be achieved.

Fertility tests for males

Male fertility levels are often assessed with a semen analysis or seminogram, a test to determine sperm quality. Seminal parameters such as volume and pH, as well as morphology, motility and concentration can be screened thanks to it.

In addition to analyzing the semen sample, karyotyping is commonly used for chromosomal screening. Given that couples struggling with infertility usually present a greater number of chromosomal abnormalities, performing a karyotype test is strongly advisable.

Furthermore, hormone testing or sperm DNA damage assessment are not required unless the specialist considers them to be necessary.

Fertility tests for females

Three main tests are involved when it comes to performing a female fertility check-up:

  • Testing for hormone levels: Basal hormone levels can be measured by means of a blood test on days 2-3 of the cycle with ovulation taking place on days 21-23.
  • Vaginal exam with pelvic ultrasound: In order to check the female reproductive system fully and measure the antral follicle count (AFC) (number of antral follicles in the ovaries, i.e. ovarian reserve).
  • Hysterosalpingography (HSG): It helps check the patency of the Fallopian tubes and determine whether infertility is caused by the impossibility for the sperm to meet the egg.

Karyotyping is also available for women. It helps us see whether there exists some kind of chromosomal alteration, as it may be the reason why the couple is experiencing trouble conceiving.

How to boost male and female fertility levels

Male and female fertility levels can be boosted naturally by simply leading a healthy lifestyle. Eating many different foods while following a balanced diet as well as doing regular exercise help increase your fertility.

Avoiding toxic substances such as alcohol, drugs and tobacco is crucial. Not only are they detrimental for your overall state of health, but also harmful to fertility.

Food supplements (vitamins and minerals) can help you boost your chances of getting pregnant. Normally, when a woman is trying to conceive, the doctor may recommend her to take daily folic acid supplements with iron.

Also, boosting foods can improve male fertility caused by poor sperm quality, especially in mild-to-moderate cases.

Unfortunately, it should be clear that treating the most severe cases of infertility with natural remedies does not always work.

FAQs from users

Until what age a woman is fertile?

By Andrea Rodrigo BSc, MSc (embryologist).

Generally, men are fertile throughout their whole life, but a woman's fertility is limited. The childbearing age range in women declines eventually from puberty to menopause, usually between ages 15-49. The optimum time period for a woman to get pregnant is between ages 18-28.

As stated earlier, female fertility drops substantially from ages 35-37 onwards. Thus, while a 20-year-old woman has a 25% chance per menstrual cycle to get pregnant naturally, this percentage is reduced to 5% by age 40 onwards.

To what extent do environmental factors affect fertility?

By Javier Domingo del Pozo MD, PhD (gynecologist).

There are several environmental pollutants that have a certain impact, especially on male fertility, such as the direct exposition to heat that takes place at some work environments, exposition to radiations, some pesticides and dioxins, etc. Also, the chemical substance Bisphenol A (BPA), which has a negative impact on fertility and is used in the production of certain materials of daily usage (such as plastics, gums, PVC...) that are difficult to avoid, as they are present for example in the layer that covers the inside of food cans.

Should men freeze their sperm to preserve their fertility?

By Dr. Rocío Núñez Calonge PhD, MSc (senior embryologist).

Although there exists different studies that relate an advanced age with fertility problems, actually it is still unclear.

In the testicle, sperm production is a permanent process, contrary to what happens in with egg production in females. This is the reason why, freezing sperm as a preventive measure is not so useful as in the case of egg freezing, since egg quality and quantity decreases from age 35 onwards.

Unless there exists a disorder that affects sperm production, in the case of cancer patients who are going to undergo chemotherapy or radiotherapy, or if the man undergoes some kind of surgery (such as in the case of vasectomy), freezing sperm for the future is not required.

How can the most fertile days to get pregnant be calculated?

By Andrea Rodrigo BSc, MSc (embryologist).

With an ovulation calendar or an ovulation test. The former allows you to find out the expected day of ovulation as long as you know the precise date of the latest menstrual cycle and the normal length of your cycles. Ovulation takes place halfway through the menstrual cycle, which means it occurs on the 14th day if it is a regular, 28-day cycle.

Ovulations tests measure a woman's LH (luteinizing hormone) levels when she is ovulating, as a surge occurs during this phase of the cycle.

Can sperm motility be improved?

By Andrea Rodrigo BSc, MSc (embryologist).

Sperm motility can be increased with food supplements, a balanced diet, moderate exercise and avoiding toxic substances such as tobacco and alcohol.

More often than not, cases of low sperm motility can be improved by making these lifestyle changes. However, the most severe cases of low sperm motility may need in vitro fertilization (IVF) with ICSI to be able to conceive.

Can you increase your sperm count quickly?

By Andrea Rodrigo BSc, MSc (embryologist).

Not exactly. Spermatogenesis, the process by which sperms are produced, takes around 2-3 months to finish. Taking this into account, an improvement in your sperm count will not happen earlier even if you follow a special diet, take supplements, avoid harmful habits, etc. It does not take place from one day to the next.

It should be clear that improvements depend on the origin of your problem. If the reason why your sperm count is low is caused by agents that are not related to your lifestyle, your sperm count is not going to improve.

Can the results of fertility tests vary over time?

By Andrea Rodrigo BSc, MSc (embryologist).

Yes, but it depends on what is causing infertility. Nonetheless, results can vary from test to test, either for the better or for the worse, as long as it is a case of temporary and treatable infertility.

A man's sperm quality can be improved if, for example, stress or an infection was the reason behind it. And the same applies in cases of women suffering from a hormonal imbalance.

However, when infertility is a consequence of cancer treatments such as chemotherapy or radiotherapy, or is caused by non-obstructive azoospermia (zero sperm count) or early menopause, we are talking about permanent infertility and improvements cannot be achieved naturally.

Is there a way to preserve fertility naturally?

By Andrea Rodrigo BSc, MSc (embryologist).

Yes, through egg and sperm cryopreservation. Although it is uncommon among men, it is becoming increasingly popular in women due to causes such as delayed motherhood and the sharp decrease in fertility levels with age. In these cases, freezing the eggs at a young age to use them for later pregnancy is advisable.

Cryopreservation is a method that gives men and women under cancer treatment the chance to become parents. Both radiotherapy and chemotherapy destroy egg- and sperm-making stem cells, and increase the likelihood for passing a genetic abnormality to offspring. This is the reason why cancer patients should choose to freeze their gametes before getting started with the treatment.

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Authors and contributors

 Andrea Rodrigo
Andrea Rodrigo
BSc, MSc
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics. More information about Andrea Rodrigo
 Javier Domingo del Pozo
Javier Domingo del Pozo
Bachelor's Degree in Medicine from the University of Alicante. Specialist in Obstetrics & Gynecology via M. I. R. at Hospital Universitario Materno-Infantil of Canarias, Spain. PhD in "Human Reproduction and Female Reproductive System Pathology" from the University of Las Palmas de Gran Canaria. Currently, he is the Director of the clinics IVI Las Palmas and IVI Tenerife. More information about Javier Domingo del Pozo
License: 353504174
Dr. Rocío Núñez Calonge
Dr. Rocío Núñez Calonge
PhD, MSc
Senior Embryologist
Bachelor's Degree in Biological Sciences from the Complutense University of Madrid. Wide experience in the scientific field, particularly as lab director. Currently, she is the Scientific Director of Clínica Tambre. More information about Dr. Rocío Núñez Calonge
Adapted into english by:
 Sandra Fernández
Sandra Fernández
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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