Subfertility and infertility are often used interchangeably, but they aren’t the same. Subfertility is a delay in conceiving. Infertility is the inability to conceive naturally after one year of trying.

In subfertility, the possibility of conceiving naturally exists, but takes longer than average. In infertility, the likelihood of conceiving without medical intervention is unlikely.

Causes of subfertility

Most of the causes of subfertility are the same as infertility. Trouble conceiving may be due to problems with male or female infertility, or a combination of both. In some cases, the cause is unknown.

Ovulation problems

The most common cause of subfertility is a problem with ovulation. Without ovulation, an egg isn’t released to be fertilized.

There are a number of conditions that can prevent ovulation, including:

  • polycystic ovary syndrome (PCOS), which can prevent ovulation or cause irregular ovulation
  • diminished ovarian reserve (DOR), which is a reduction in a woman’s egg count due to aging or other causes, such as a medical condition or previous ovarian surgery
  • premature ovarian insufficiency (POI)Trusted Source, also referred to as premature menopause, in which ovaries fail before the age of 40 due to either a medical condition or treatment, such as chemotherapy
  • hypothalamus and pituitary gland conditions, which interfere with the ability to produce the hormones needed to maintain normal ovarian function

Fallopian tube obstruction

Blocked fallopian tubes prevent the egg from meeting the sperm. It can be caused by:

  • endometriosis
  • pelvic inflammatory disease (PID)
  • scar tissue from a previous surgery, such as a surgery for ectopic pregnancy
  • a history of gonorrhea or chlamydia

Uterine abnormalities

The uterus, also called the womb, is where your baby grows. Abnormalities or defects in the uterus can interfere with your ability to get pregnant. This can include congenital uterine conditions, which are present at birth, or an issue that develops later.

Some uterine conditions include:

  • septate uterus, in which a band of tissue divides the uterus into two sections
  • bicornuate uterus, in which the uterus has two cavities instead of one, resembling the shape of a heart
  • double uterus, in which the uterus has two small cavities, each with its own opening
  • fibroids, which are abnormal growths inside or on the uterus

Problems with sperm production or function

Abnormal sperm production or function can cause subfertility. This can be caused by a number of conditions and factors, including:

  • gonorrhea
  • chlamydia
  • HIV
  • diabetes
  • mumps
  • cancer and cancer treatment
  • enlarged veins in the testes, called varicocele
  • genetic defects, such as Klinefelter syndrome

Problems with sperm delivery

Problems with the delivery of sperm can make it difficult to conceive. This can be caused by a number of things, including:

  • genetic conditions, such as cystic fibrosis
  • premature ejaculation
  • injury or damage to the testes
  • structural defects, such as a blockage in the testicle