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Subfertility and Infertility - An Overview

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Fertility complications are seen affecting every one out of five couples. Two of the most common factors associated with it are infertility and subfertility.

Medically reviewed by

Dr. Sameer Kumar

Published At June 6, 2023
Reviewed AtApril 15, 2024


Fertility-related complications are growing in numbers day day day. Around 48 million couples and 186 million people worldwide suffer from infertility worldwide. These complications have grave psychological, social, and personal impacts. Understanding and knowledge about fertility-related disorders will help eradicate these conditions. Two of the most commonly encountered fertility-related conditions are infertility and subfertility.

What Is Infertility?

Globally around 10 percent of women are suffering from infertility. Infertility is being unable to get pregnant even after having unprotected sex for more than one year.

What Is Subfertility?

Substerlity is characterized by inability to get pregnant after one year of regular unprotected sexual intercourse. In this condition, ovulation, tubal patency, and semen analysis are normal. This of two types:

  1. Primary Subfertility: This is seen in women who have never been pregnant or in men who have never made any women pregnant.

  2. Secondary Subfertility: This is seen in women who were pregnant before but are unable to conceive. Or men who made women pregnant before could not do so in their present condition.

The main difference between infertility and subfertility is that in subfertility, it usually takes longer than normal to conceive. And couples go through certain medical procedures like IVF (in-vitro fertilization) to conceive. But in infertility, the couple can't conceive a child.

What Are the Causes?

Thirty-seven percent of cases of infertility are related to female infertility. The conditions related to female infertility and subfertility are:

  • Ovulatory Disorders: Ovulatory disorders are the leading cause of infertility in women. Around 25 percent of cases are related to such conditions. These conditions are responsible for the impaired release of eggs (anovulation). The causative factors for such conditions are:

  • Hypogonadotropic Hypogonadal Anovulation: Excessive exercise, reduced calorie intake, eating disorders, and obesity is responsible for increased secretion of Gonadotropin-releasing hormone (GnRH, regulatory hormone for periods). As a result, the amount of cortisol (a steroid hormone) in the blood is elevated. These cause decreased secretion of hormones responsible for period and ovulation (release of eggs).

  • Normogonadotropic Normoestrogenic Anovulation: Conditions like polycystic ovary (PCOS) belongs to this category. Around 5 to 20 percent of women of reproductive age suffer from conditions like this. In such conditions, the level of androgen (male sex hormone) remains high. As a result, the level of it levels of luteinizing hormone (LH) and gonadotropin-releasing hormone (GnRH) are elevated and the ratio between luteinizing hormone (LH) and follicular-stimulating hormone (FSH) is changed. This causes alteration in the period cycle and ovulation is disrupted. PCOS causes around 80 percent of cases of anovulation. Also, elevated levels of the anti-Mullerian hormone (AMH, a hormone that helps in folliculogenesis) are related to the cystic appearance of the ovary.

  • Hypergonadotropic Hypoestrogenic Anovulation: These conditions are responsible for premature ovarian insufficiency or ovarian resistance. The primary factor that is associated with this condition is the decline in the quality and quantity of the patient’s egg. At the time of birth, the number of eggs is around 1 million. At puberty, the number of eggs is 300,000, and the gradual loss of eggs occurs with age progression. But, sometimes, the rate of losing the egg is increased. Various factors like increased age, smoking, and chronic alcoholism precipitate such conditions.

  • Hypergonadotropic Hypogonadism: This happens when ovaries stop working normally before age 40. Usually, women stop producing eggs at around the age of 45. But in certain cases, women stop having periods suddenly due to primary ovarian insufficiency. In this condition, low level of estrogen and loss of eggs. The disorders associated with such conditions are autoimmune disorders like rheumatoid arthritis, Turner’s syndrome (X-chromosome-linked disorder), and chemotherapy.

  • Endometriosis: This condition is characterized by the presence ofovary-like tissue outside the ovary. In such conditions, such tissues are present in places like the pleura (covering the lungs), the pericardium (covering the heart), the rectum, the bowl, or the central nervous system. This condition can be found in 10 to 15 percent of women of reproductive age. The minimal form of endometritis (stage I and stage II) is associated with increased secretion of inflammatory mediators, increased functioning of macrophages, and natural killer cells. These factors prevent the implantation of the fertilized egg and are associated with subfertility. On the other hand, a severe form of endometritis (stage III and Stage IV) is associated with the presence of pelvic adhesion and the presence of masses, and distorted pelvic anatomy. These factors are associated with infertility.

  • Pelvic or Tubal Adhesions: In these conditions, genital structures are stuck together. These factors lead to tubal abnormality and tubal blockage. As a result, the muscular action of the tube, normal passage of the sperm, and implantation of the fertilized egg are impaired. Pelvic inflammatory diseases (PID) are also associated with such conditions. Several infectious conditions, such as gonorrhea and chlamydia, can cause PID. A milder form of such infection is a tubal function defect without causing total occlusion. These functional defects are associated with subfertility.

  • Uterine Abnormalities: Anatomical abnormalities of uterine structures are associated with such conditions. The presence of leiomyomas (fibroids, growth of muscle and connective tissues) and scar tissue is associated with these conditions. Additionally, structural abnormalities like the presence of a septum, double uterus, one-sided uterus, and bicornuate uterus (heart-shaped uterus) are responsible for infertility.

Not only female males are also equally responsible for fertility-related complexities. These conditions are:

  • Poor Semen Quality: Poor semen quality is the key cause of fertility-related problems. These problems can be of various types, such as less quantity of semen, altered pH of the semen, increased motility of the sperm, and less sperm count the semen. These are caused by various factors like:

  • External Factors: Increased stress, smoking, obesity, and alcoholism is associated with decreased sperm count and sperm mortality rate.

  • Pre-Testicular Factors: Conditions like hypogonadotropic hypogonadism (decreased production of male hormone) and erectile dysfunction (unable to produce sufficient erection) are associated with decreased sperm count.

  • Testicular Disorders: Testicular tumors and varicoceles (increased diameter of blood vessels around testicles) are responsible for decreased sperm count. Epididymal dysfunctions (path for passage of sperm) are responsible for DNA dysfunction of sperm and impaired semen parameters.

  • Post-Testicular Factors: Lesions in the seminal tract (part of the male reproductive tract), inflammation is vas difference (tubes which carry sperm out of the testis), infections, and diseases like gonorrhea are responsible for defective sperm formations.


Fertility disorders are global problems. Both men and women can be affected by these conditions. External factors include lifestyle, food habits, and smoking is also associated with these problems. Also, infectious diseases, anatomical malformations, and hormonal disorders are responsible for infertility and subfertility. Poper diagnostic tests such as ultrasonography and semen analysis are necessary to differentiate between infertility and subfertility. With the help of modern medical procedures like in-vitro fertilization, treatment of subfertility is also possible.

Dr. Sameer Kumar
Dr. Sameer Kumar

Obstetrics and Gynecology


infertilitysubfertility and infertilityfemale subfertility
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