Causes of Infertility

Ovulation Disorders

A female is born with millions of eggs.  Each month, several hundred to one thousand eggs are eligible for ovulation. Hormonal changes throughout the menstrual cycle, as well as local events within the ovary, typically allow only one egg to be released during a single menstrual cycle.

Eggs develop inside a water balloon-like structure called a follicle.  The release of luteinizing hormone (LH) then triggers ovulation (the release of an egg from a follicle). After ovulation, the dominant follicle produces progesterone, which is critical for maintaining a receptive uterine lining, or endometrium, where a fertilized egg may implant.

If pregnancy is established, the placenta makes the hormone human chorionic gonadotropin (hCG). hCG levels rise sharply during early pregnancy and forces the dominant follicle (now called a corpus luteum) to make progesterone until the placenta takes over making progesterone. This occurs at approximately eight weeks gestation. If pregnancy is not established, the corpus luteum dissolves and progesterone levels fall, triggering a menstrual period.

Most women ovulate every 21 to 35 days. Women with cycles greater than 35 days are considered to have oligo-ovulation. Those who do not ovulate at all have anovulation. Medical therapy is often successful in these cases.

There are a number of reasons why women do not have regular cycles. Some reasons include polycystic ovarian syndrome (PCOS), thyroid disorder and adrenal gland problems. Excessive exercise or weight loss can also cause problems with ovulation. An evaluation including hormone and other blood testing, as well as ultrasound, is performed to determine the cause of the irregular cycles.

Fertility medications help to encourage the development of eggs within the ovaries. These medications – such as clomiphene citrate and injectable gonadotropins – often stimulate the ovaries to mature more than one egg in a cycle.  Women undergoing ovulation induction or IVF will frequently be given progesterone during the luteal phase (the two weeks after ovulation) to help support the endometrium. 

Learn more about infertility medications.

Other Causes of Infertility:

• Tubal Disease
• Endometriosis
• Diminished Ovarian Reserve
• Fibroids
• Uterine Receptivity
• Male Factor
• Recurrent Pregnancy Loss

 

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