What is the Difference Between Infertility and Subfertility

The main difference between infertility and subfertility is that people with infertility need medical assistance to get pregnant, whereas people with subfertility still have a chance to get pregnant on their own.

Infertility and subfertility are two conditions we encounter in couples trying to conceive a baby. Furthermore, an infertile person may have been trying to get pregnant for at least one year without success while a person with subfertility takes longer than average to get pregnant.  

Key Areas Covered 

1. What is Infertility
     – Definition, Characteristics, Causes
2. What is Subfertility
     – Definition, Characteristics, Types
3. What are the Similarities Between Infertility and Subfertility
     – Outline of Common Features
4. What is the Difference Between Infertility and Subfertility
     – Comparison of Key differences

Key Terms 

Combined Infertility, Infertility, Primary Infertility, Secondary Infertility, Subfertility, Unexplained Infertility

What is Infertility 

Infertility is the inability of animals or plants to reproduce naturally. However, in humans, it refers to the inability of getting pregnant for more than one year. Generally, infertility is synonymous with sterility, with only sporadically occurring spontaneous pregnancies. The definition of infertility based on the World Health Organization is “a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse (and there is no other reason, such as breastfeeding or postpartum amenorrhoea)”. 

Figure 1: Contribution of Infertility Causes

Furthermore, there are two types of infertility: primary and secondary infertility. Primary infertility refers to infertility in a couple who have never had a child. In contrast, secondary infertility is the failure to conceive following a previous pregnancy. Moreover, the three main causes of infertility include immune infertility, sexually-transmitted diseases, and genetic infertility. Anti-sperm antibodies cause about10-30% infertility. Some sexually-transmitted pathogens, including  Chlamydia trachomatis and Neisseria gonorrhoeae, also cause infertility. Additionally, female tract syndrome and Mycoplasma genitalium infection may cause infertility. On the other hand, the mutations to the NR5A1 gene, which encode SF-1 in men can cause infertility. Furthermore, other causes of infertility include DNA damage, general factors such as diabetes, thyroid disorders, etc., hypothalamic-pituitary factors, and environmental factors such as tobacco smoking. 

What is Subfertility 

Subfertility is the form of reduced fertility characterized by the prolonged time of unwanted non-conception. Generally, the time of unwanted non-conception is the main factor determining the grading of subfertility of an individual. According to a study, 80% of couples would conceive after six months. Moreover, 10% of them would conceive after another six months. Also, another 5% would conceive spontaneously within the next 36 months. However, the last 5% would be extremely unlikely to conceive ever. Therefore, the couples who had been trying to get pregnant for 48 months have a zero chance to conceive without medical assistance.

Figure 2: IVF

Moreover, both subfertility, as well as infertility, have the same causes; they may also vary by partner. Generally, the main causes of subfertility in women include ovulation problems and age-related factors. In contrast, in men, the main cause is the lower sperm count than normal. However, in some cases, both partners show combined characteristics of subfertility. On the other hand, many couples with subfertility are diagnosed with unexplained infertility. Furthermore, some basic fertility tests include ovarian ultrasound, HCG, semen analysis, hormone testing in females, and genetic testing. Moreover, in vitro fertilization and intracytoplasmic sperm injection are the two basic types of treatment for infertility. 

Similarities Between Infertility and Subfertility 

• Infertility and subfertility are two conditions in couples trying to conceive a baby. 
• Both conditions take longer time to get pregnant than normal. 

Difference Between Infertility and Subfertility 

Definition 

Infertility refers to a condition that can be synonymous with sterility with only sporadically occurring spontaneous pregnancies while subfertility refers to any form of reduced fertility with prolonged time of unwanted non-conception.   

Significance 

Infertility indicates that the couple has been trying to get pregnant for at least one year without success while a person with subfertility takes longer than average to get pregnant. 

Medical Assistance 

Infertility needs medical assistance to get pregnant while subfertility still has a chance to get pregnant on their own.  

Percentage 

About 5% of the couples have the unresolved problem with infertility while different levels of subfertility are there based on the time taken to get pregnant. 

Causes 

The three main causes of infertility include immune infertility, sexually-transmitted diseases, and genetic infertility while ovulation problems and age-related factors in women and the lower sperm count than normal in men are the main causes of subfertility. 

Conclusion 

Infertility is the condition with couples who are unable to get pregnant for at least one year. Therefore, they need medical assistance to get pregnant. On the other hand, subfertility is the condition which takes a longer time to get pregnant than normal. However, it has the chance to get pregnant on their own. Hence, the main difference between infertility and subfertility is the time taken to get pregnant and the requirement of medical assistance. 

References:

1. C. Gnoth, E. Godehardt, P. Frank-Herrmann, K. Friol, Jürgen Tigges, G. Freundl, Definition and prevalence of subfertility and infertility, Human Reproduction, Volume 20, Issue 5, May 2005, Pages 1144–1147, https://doi.org/10.1093/humrep/deh870
2. Gurevich, Rachel. “Subfertility and Infertility Causes and Treatment Options.” Verywell Family, 23 Oct. 2018, Available Here.

Image Courtesy:

1. “Infertility causes” By Mikael Häggström – Own work (Public Domain) via Commons Wikimedia   
2. “IVF” By Manu5 (CC BY-SA 4.0) via Commons Wikimedia