Infertility: Causes and Overview

Infertility is a common problem that affects around 15 percent of couples planetwide. It is defined as being unable to become pregnant within one year of regular, unprotected intercourse. In general, infertility investigations are only recommended for couples who have not been able to conceive after 12 months, unless the woman is over 35 years old, in which case doctors may start investigations earlier to compensate for declining fertility with age. Infertility can be primary, meaning that a couple has never had a child, or secondary, meaning that a couple has had children in the past but is now struggling to produce additional children.

To understand the causes of infertility, it is important to consider all the steps involved in becoming pregnant, so let’s go through those now. First of all, you and your partner should engage in regular sexual intercourse without contraception, every two to three days. For pregnancy to begin, an ovum must be fertilized. This happens in the days following sexual intercourse and it requires the woman to have ovulated, meaning that she has released an ovum (an egg) from one of her two ovaries. Usually, this occurs around day 14 of a 28-29-day menstrual cycle, but this can vary depending on the length of the cycle. Of hundreds of millions of sperm cells enter the vagina, only about one in ten thousand —a couple of hundred in total— are able to swim all the way to the fallopian tube, and there, come into contact with an ovum that is en route through the tube, bound for the uterus. There is a fertile window spanning about four days surrounding ovulation, when sperm cells have the best opportunity to meet an egg that is ripe for fertilization.

There are several potential causes of infertility, including problems with sperm production or quality in men, and issues with ovulation, the fallopian tubes, or the uterus in women. In men, infertility can be caused by a variety of factors, including low sperm count, poor sperm quality, and problems with the reproductive system such as a varicocele, a condition that causes the veins in the testicles to become enlarged. In women, common causes of infertility include problems with ovulation, such as polycystic ovary syndrome (PCOS), which generally causes long cycles and thus relatively infrequent ovulation. Infertility also can result from damage to the fallopian tubes, notably pelvic inflammatory disease (PID). In PID, there is inflammation of the female reproductive organs and the surrounding area. In particular, PID features inflammation of the cervix (cervicitis), the fallopian tubes (salpingitis), the lining of the uterus (endometritis), and the membrane that lines the pelvic and abdominal cavities (peritonitis). Typically, the inflammation is due to a bacterial infection, usually with the species Chlamydia trachomatis or Neisseria gonorrhoeae, which are sexually transmitted infections (STIs). But you also can develop PID from non-sexual infections of bacteria coming either from outside, or from your body. Such non-sexual infections can result from foreign objects in your reproductive tract, such as a douche or tampon (especially if left in too long) or occasionally from an intrauterine device (IUD) inserted for birth control. It is unusual for women to develop PID during pregnancy, but when it does happen during pregnancy, usually it is during the first trimester.

Other factors that can contribute to infertility include age, weight, certain medical conditions, and certain medications. For example, women who are overweight or obese may have difficulty becoming pregnant due to hormonal imbalances, while men who are overweight or obese may have problems with sperm production. Certain medical conditions, such as diabetes and thyroid disorders, can also affect fertility. In addition, certain medications, including certain types of chemotherapy and radiation therapy, can cause infertility.

To diagnose and treat infertility, various tests and procedures may be used, including semen analysis, hormonal testing, imaging tests, and assisted reproductive technologies such as in vitro fertilization (IVF). Semen analysis involves examining a sample of a man’s semen to assess the number and quality of his sperm. Hormonal testing involves checking the levels of certain hormones in the body, such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are involved in the menstrual cycle and ovulation. Imaging tests, such as ultrasound, can be used to visualize the uterus, fallopian tubes, and ovaries and check for abnormalities.

Assisted reproductive technologies, such as IVF, involve fertilizing an egg outside of the body and then transferring the fertilized egg back into the uterus. IVF can be an effective treatment for infertility caused by various factors, including problems with the fallopian tubes or uterus, problems with sperm production or quality, and unexplained infertility. It is important to work with a healthcare provider to determine the cause of infertility and develop a treatment plan. While not all causes of infertility can be treated, many couples are able to become pregnant with the help of medical interventions. It is also important to remember that infertility is not the sole responsibility of one partner and that both partners should be involved in the process of diagnosis.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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